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650 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
David Hildenbrand
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3dfde97800 |
mm: add get_and_clear_ptes() and clear_ptes()
Patch series "Optimizations for khugepaged", v4. If the underlying folio mapped by the ptes is large, we can process those ptes in a batch using folio_pte_batch(). For arm64 specifically, this results in a 16x reduction in the number of ptep_get() calls, since on a contig block, ptep_get() on arm64 will iterate through all 16 entries to collect a/d bits. Next, ptep_clear() will cause a TLBI for every contig block in the range via contpte_try_unfold(). Instead, use clear_ptes() to only do the TLBI at the first and last contig block of the range. For split folios, there will be no pte batching; the batch size returned by folio_pte_batch() will be 1. For pagetable split folios, the ptes will still point to the same large folio; for arm64, this results in the optimization described above, and for other arches, a minor improvement is expected due to a reduction in the number of function calls and batching atomic operations. This patch (of 3): Let's add variants to be used where "full" does not apply -- which will be the majority of cases in the future. "full" really only applies if we are about to tear down a full MM. Use get_and_clear_ptes() in existing code, clear_ptes() users will be added next. Link: https://lkml.kernel.org/r/20250724052301.23844-2-dev.jain@arm.com Signed-off-by: David Hildenbrand <david@redhat.com> Signed-off-by: Dev Jain <dev.jain@arm.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Reviewed-by: Barry Song <baohua@kernel.org> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Zi Yan <ziy@nvidia.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Mariano Pache <npache@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Ryan Roberts
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a9e056de66 |
mm: remove arch_flush_tlb_batched_pending() arch helper
Since commit |
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David Hildenbrand
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dd80cfd487 |
mm: split folio_pte_batch() into folio_pte_batch() and folio_pte_batch_flags()
Many users (including upcoming ones) don't really need the flags etc, and can live with the possible overhead of a function call. So let's provide a basic, non-inlined folio_pte_batch(), to avoid code bloat while still providing a variant that optimizes out all flag checks at runtime. folio_pte_batch_flags() will get inlined into folio_pte_batch(), optimizing out any conditionals that depend on input flags. folio_pte_batch() will behave like folio_pte_batch_flags() when no flags are specified. It's okay to add new users of folio_pte_batch_flags(), but using folio_pte_batch() if applicable is preferred. So, before this change, folio_pte_batch() was inlined into the C file optimized by propagating constants within the resulting object file. With this change, we now also have a folio_pte_batch() that is optimized by propagating all constants. But instead of having one instance per object file, we have a single shared one. In zap_present_ptes(), where we care about performance, the compiler already seem to generate a call to a common inlined folio_pte_batch() variant, shared with fork() code. So calling the new non-inlined variant should not make a difference. While at it, drop the "addr" parameter that is unused. Link: https://lkml.kernel.org/r/20250702104926.212243-4-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Suggested-by: Andrew Morton <akpm@linux-foundation.org> Link: https://lore.kernel.org/linux-mm/20250503182858.5a02729fcffd6d4723afcfc2@linux-foundation.org/ Reviewed-by: Oscar Salvador <osalvador@suse.de> Reviewed-by: Zi Yan <ziy@nvidia.com> Reviewed-by: Dev Jain <dev.jain@arm.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Gregory Price <gourry@gourry.net> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Jann Horn <jannh@google.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Lance Yang <lance.yang@linux.dev> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Mathew Brost <matthew.brost@intel.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Rik van Riel <riel@surriel.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
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e66d7a4f55 |
mm: convert FPB_IGNORE_* into FPB_RESPECT_*
Patch series "mm: folio_pte_batch() improvements", v2. Ever since we added folio_pte_batch() for fork() + munmap() purposes, a lot more users appeared (and more are being proposed), and more functionality was added. Most of the users only need basic functionality, and could benefit from a non-inlined version. So let's clean up folio_pte_batch() and split it into a basic folio_pte_batch() (no flags) and a more advanced folio_pte_batch_ext(). Using either variant will now look much cleaner. This series will likely conflict with some changes in some (old+new) folio_pte_batch() users, but conflicts should be trivial to resolve. This patch (of 4): Respecting these PTE bits is the exception, so let's invert the meaning. With this change, most callers don't have to pass any flags. This is a preparation for splitting folio_pte_batch() into a non-inlined variant that doesn't consume any flags. Long-term, we want folio_pte_batch() to probably ignore most common PTE bits (e.g., write/dirty/young/soft-dirty) that are not relevant for most page table walkers: uffd-wp and protnone might be bits to consider in the future. Only walkers that care about them can opt-in to respect them. No functional change intended. Link: https://lkml.kernel.org/r/20250702104926.212243-2-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Lance Yang <lance.yang@linux.dev> Reviewed-by: Zi Yan <ziy@nvidia.com> Reviewed-by: Oscar Salvador <osalvador@suse.de> Reviewed-by: Dev Jain <dev.jain@arm.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Gregory Price <gourry@gourry.net> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Jann Horn <jannh@google.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Mathew Brost <matthew.brost@intel.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Rik van Riel <riel@surriel.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
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df25569d40 |
mm: rename PAGE_MAPPING_* to FOLIO_MAPPING_*
Now that the mapping flags are only used for folios, let's rename the defines. Link: https://lkml.kernel.org/r/20250704102524.326966-27-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Zi Yan <ziy@nvidia.com> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Harry Yoo <harry.yoo@oracle.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Brendan Jackman <jackmanb@google.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Chengming Zhou <chengming.zhou@linux.dev> Cc: Christian Brauner <brauner@kernel.org> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: Eugenio Pé rez <eperezma@redhat.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Gregory Price <gourry@gourry.net> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Jan Kara <jack@suse.cz> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jason Wang <jasowang@redhat.com> Cc: Jerrin Shaji George <jerrin.shaji-george@broadcom.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Madhavan Srinivasan <maddy@linux.ibm.com> Cc: Mathew Brost <matthew.brost@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Naoya Horiguchi <nao.horiguchi@gmail.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Peter Xu <peterx@redhat.com> Cc: Qi Zheng <zhengqi.arch@bytedance.com> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Rik van Riel <riel@surriel.com> Cc: Sergey Senozhatsky <senozhatsky@chromium.org> Cc: Shakeel Butt <shakeel.butt@linux.dev> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com> Cc: xu xin <xu.xin16@zte.com.cn> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Andrew Morton
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cac3d177c0 |
Merge branch 'mm-hotfixes-stable' into mm-stable to pick up changes which
are required for a merge of the series "mm: folio_pte_batch() improvements". |
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Lorenzo Stoakes
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bfbe71109f |
mm: update core kernel code to use vm_flags_t consistently
The core kernel code is currently very inconsistent in its use of vm_flags_t vs. unsigned long. This prevents us from changing the type of vm_flags_t in the future and is simply not correct, so correct this. While this results in rather a lot of churn, it is a critical pre-requisite for a future planned change to VMA flag type. Additionally, update VMA userland tests to account for the changes. To make review easier and to break things into smaller parts, driver and architecture-specific changes is left for a subsequent commit. The code has been adjusted to cascade the changes across all calling code as far as is needed. We will adjust architecture-specific and driver code in a subsequent patch. Overall, this patch does not introduce any functional change. Link: https://lkml.kernel.org/r/d1588e7bb96d1ea3fe7b9df2c699d5b4592d901d.1750274467.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Acked-by: Kees Cook <kees@kernel.org> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org> Acked-by: Jan Kara <jack@suse.cz> Acked-by: Christian Brauner <brauner@kernel.org> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Oscar Salvador <osalvador@suse.de> Reviewed-by: Pedro Falcato <pfalcato@suse.de> Acked-by: Zi Yan <ziy@nvidia.com> Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Jann Horn <jannh@google.com> Cc: Liam R. Howlett <Liam.Howlett@oracle.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Lance Yang
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ddd05742b4 |
mm/rmap: fix potential out-of-bounds page table access during batched unmap
As pointed out by David[1], the batched unmap logic in
try_to_unmap_one() may read past the end of a PTE table when a large
folio's PTE mappings are not fully contained within a single page
table.
While this scenario might be rare, an issue triggerable from userspace
must be fixed regardless of its likelihood. This patch fixes the
out-of-bounds access by refactoring the logic into a new helper,
folio_unmap_pte_batch().
The new helper correctly calculates the safe batch size by capping the
scan at both the VMA and PMD boundaries. To simplify the code, it also
supports partial batching (i.e., any number of pages from 1 up to the
calculated safe maximum), as there is no strong reason to special-case
for fully mapped folios.
Link: https://lkml.kernel.org/r/20250701143100.6970-1-lance.yang@linux.dev
Link: https://lkml.kernel.org/r/20250630011305.23754-1-lance.yang@linux.dev
Link: https://lkml.kernel.org/r/20250627062319.84936-1-lance.yang@linux.dev
Link: https://lore.kernel.org/linux-mm/a694398c-9f03-4737-81b9-7e49c857fcbe@redhat.com [1]
Fixes:
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Ye Liu
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0ca954046c |
mm/rmap: fix typo in comment in page_address_in_vma
Fix a minor typo in the comment above page_address_in_vma(): "responsibililty" → "responsibility" Link: https://lkml.kernel.org/r/20250421085729.127845-3-ye.liu@linux.dev Signed-off-by: Ye Liu <liuye@kylinos.cn> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Harry Yoo <harry.yoo@oracle.com> Cc: David Hildenbrand <david@redhat.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Naoya Horiguchi <nao.horiguchi@gmail.com> Cc: Rik van Riel <riel@surriel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Ye Liu
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f04cc63dc7 |
mm/rmap: rename page__anon_vma to anon_vma for consistency
Patch series "mm: minor cleanups in rmap", v3. Minor cleanups in mm/rmap.c: - Rename a local variable for consistency - Fix a typo in a comment No functional changes. This patch (of 2): Rename local variable page__anon_vma in page_address_in_vma() to anon_vma. The previous naming convention of using double underscores (__) is unnecessary and inconsistent with typical kernel style, which uses single underscores to denote local variables. Also updated comments to reflect the new variable name. Functionality unchanged. Link: https://lkml.kernel.org/r/20250421085729.127845-1-ye.liu@linux.dev Link: https://lkml.kernel.org/r/20250421085729.127845-2-ye.liu@linux.dev Signed-off-by: Ye Liu <liuye@kylinos.cn> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Harry Yoo <harry.yoo@oracle.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Liu Ye <liuye@kylinos.cn> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Naoya Horiguchi <nao.horiguchi@gmail.com> Cc: Rik van Riel <riel@surriel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Gavin Guo
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b960818d51 |
mm/huge_memory: remove useless folio pointers passing
Since the previous commit "mm/huge_memory: Adjust try_to_migrate_one() and split_huge_pmd_locked()" has simplified the logic by leveraging the folio verification in page_vma_mapped_walk(), this patch removes the unnecessary folio pointers passing. Link: https://lkml.kernel.org/r/20250425103859.825879-3-gavinguo@igalia.com Link: https://lore.kernel.org/all/98d1d195-7821-4627-b518-83103ade56c0@redhat.com/ Link: https://lore.kernel.org/all/91599a3c-e69e-4d79-bac5-5013c96203d7@redhat.com/ Signed-off-by: Gavin Guo <gavinguo@igalia.com> Suggested-by: David Hildenbrand <david@redhat.com> Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Zi Yan <ziy@nvidia.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Florent Revest <revest@google.com> Cc: Gavin Shan <gshan@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Gavin Guo
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60fbb14396 |
mm/huge_memory: adjust try_to_migrate_one() and split_huge_pmd_locked()
Patch series "Clean up split_huge_pmd_locked() and remove unnecessary folio pointers", v2. The patch series enhances the folio verification by leveraging the existing page_vma_mapped_walk() mechanism and removing redundant folio pointer passing. This patch (of 2): split_huge_pmd_locked() currently performs redundant checks for migration entries and folio validation that are already handled by the page_vma_mapped_walk mechanism in try_to_migrate_one. Specifically, page_vma_mapped_walk already ensures that: - The folio is properly mapped in the given VMA area - pmd_trans_huge, pmd_devmap, and migration entry validation are performed To leverage page_vma_mapped_walk's work, moving TTU_SPLIT_HUGE_PMD handling to the while loop checking and removing these duplicate checks from split_huge_pmd_locked. Link: https://lkml.kernel.org/r/20250425103859.825879-1-gavinguo@igalia.com Link: https://lkml.kernel.org/r/20250425103859.825879-2-gavinguo@igalia.com Link: https://lore.kernel.org/all/98d1d195-7821-4627-b518-83103ade56c0@redhat.com/ Link: https://lore.kernel.org/all/91599a3c-e69e-4d79-bac5-5013c96203d7@redhat.com/ Signed-off-by: Gavin Guo <gavinguo@igalia.com> Suggested-by: David Hildenbrand <david@redhat.com> Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Zi Yan <ziy@nvidia.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Florent Revest <revest@google.com> Cc: Gavin Shan <gshan@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
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749492229e |
mm: stop maintaining the per-page mapcount of large folios (CONFIG_NO_PAGE_MAPCOUNT)
Everything is in place to stop using the per-page mapcounts in large
folios: the mapcount of tail pages will always be logically 0 (-1 value),
just like it currently is for hugetlb folios already, and the page
mapcount of the head page is either 0 (-1 value) or contains a page type
(e.g., hugetlb).
Maintaining _nr_pages_mapped without per-page mapcounts is impossible, so
that one also has to go with CONFIG_NO_PAGE_MAPCOUNT.
There are two remaining implications:
(1) Per-node, per-cgroup and per-lruvec stats of "NR_ANON_MAPPED"
("mapped anonymous memory") and "NR_FILE_MAPPED"
("mapped file memory"):
As soon as any page of the folio is mapped -- folio_mapped() -- we
now account the complete folio as mapped. Once the last page is
unmapped -- !folio_mapped() -- we account the complete folio as
unmapped.
This implies that ...
* "AnonPages" and "Mapped" in /proc/meminfo and
/sys/devices/system/node/*/meminfo
* cgroup v2: "anon" and "file_mapped" in "memory.stat" and
"memory.numa_stat"
* cgroup v1: "rss" and "mapped_file" in "memory.stat" and
"memory.numa_stat
... can now appear higher than before. But note that these folios do
consume that memory, simply not all pages are actually currently
mapped.
It's worth nothing that other accounting in the kernel (esp. cgroup
charging on allocation) is not affected by this change.
[why oh why is "anon" called "rss" in cgroup v1]
(2) Detecting partial mappings
Detecting whether anon THPs are partially mapped gets a bit more
unreliable. As long as a single MM maps such a large folio
("exclusively mapped"), we can reliably detect it. Especially before
fork() / after a short-lived child process quit, we will detect
partial mappings reliably, which is the common case.
In essence, if the average per-page mapcount in an anon THP is < 1,
we know for sure that we have a partial mapping.
However, as soon as multiple MMs are involved, we might miss detecting
partial mappings: this might be relevant with long-lived child
processes. If we have a fully-mapped anon folio before fork(), once
our child processes and our parent all unmap (zap/COW) the same pages
(but not the complete folio), we might not detect the partial mapping.
However, once the child processes quit we would detect the partial
mapping.
How relevant this case is in practice remains to be seen.
Swapout/migration will likely mitigate this.
In the future, RMAP walkers could check for that for that case
(e.g., when collecting access bits during reclaim) and simply flag
them for deferred-splitting.
Link: https://lkml.kernel.org/r/20250303163014.1128035-21-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andy Lutomirks^H^Hski <luto@kernel.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: Michal Koutn <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: tejun heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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David Hildenbrand
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003fde4492 |
mm: convert folio_likely_mapped_shared() to folio_maybe_mapped_shared()
Let's reuse our new MM ownership tracking infrastructure for large folios
to make folio_likely_mapped_shared() never return false negatives -- never
indicating "not mapped shared" although the folio *is* mapped shared.
With that, we can rename it to folio_maybe_mapped_shared() and get rid of
the dependency on the mapcount of the first folio page.
The semantics are now arguably clearer: no mixture of "false negatives"
and "false positives", only the remaining possibility for "false
positives".
Thoroughly document the new semantics. We might now detect that a large
folio is "maybe mapped shared" although it *no longer* is -- but once was.
Now, if more than two MMs mapped a folio at the same time, and the MM
mapping the folio exclusively at the end is not one tracked in the two
folio MM slots, we will detect the folio as "maybe mapped shared".
For anonymous folios, usually (except weird corner cases) all PTEs that
target a "maybe mapped shared" folio are R/O. As soon as a child process
would write to them (iow, actively use them), we would CoW and effectively
replace these PTEs. Most cases (below) are not expected to really matter
with large anonymous folios for this reason.
Most importantly, there will be no change at all for:
* small folios
* hugetlb folios
* PMD-mapped PMD-sized THPs (single mapping)
This change has the potential to affect existing callers of
folio_likely_mapped_shared() -> folio_maybe_mapped_shared():
(1) fs/proc/task_mmu.c: no change (hugetlb)
(2) khugepaged counts PTEs that target shared folios towards
max_ptes_shared (default: HPAGE_PMD_NR / 2), meaning we could skip a
collapse where we would have previously collapsed. This only applies
to anonymous folios and is not expected to matter in practice.
Worth noting that this change sorts out case (A) documented in
commit
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David Hildenbrand
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448854478a |
mm/rmap: use folio_large_nr_pages() in add/remove functions
Let's just use the "large" variant in code where we are sure that we have a large folio in our hands: this way we are sure that we don't perform any unnecessary "large" checks. While at it, convert the VM_BUG_ON_VMA to a VM_WARN_ON_ONCE. Maybe in the future there will not be a difference in that regard between large and small folios; in that case, unifying the handling again will be easy. E.g., folio_large_nr_pages() will simply translate to folio_nr_pages() until we replace all instances. Link: https://lkml.kernel.org/r/20250303163014.1128035-12-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Andy Lutomirks^H^Hski <luto@kernel.org> Cc: Borislav Betkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Lance Yang <ioworker0@gmail.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcow (Oracle) <willy@infradead.org> Cc: Michal Koutn <mkoutny@suse.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: tejun heo <tj@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Zefan Li <lizefan.x@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
David Hildenbrand
|
932961c4b6 |
mm/rmap: abstract large mapcount operations for large folios (!hugetlb)
Let's abstract the operations so we can extend these operations easily. Link: https://lkml.kernel.org/r/20250303163014.1128035-10-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Andy Lutomirks^H^Hski <luto@kernel.org> Cc: Borislav Betkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Lance Yang <ioworker0@gmail.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcow (Oracle) <willy@infradead.org> Cc: Michal Koutn <mkoutny@suse.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: tejun heo <tj@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Zefan Li <lizefan.x@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
David Hildenbrand
|
1862a4af10 |
mm/rmap: pass vma to __folio_add_rmap()
We'll need access to the destination MM when modifying the mapcount large folios next. So pass in the VMA. Link: https://lkml.kernel.org/r/20250303163014.1128035-9-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Andy Lutomirks^H^Hski <luto@kernel.org> Cc: Borislav Betkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Lance Yang <ioworker0@gmail.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Matthew Wilcow (Oracle) <willy@infradead.org> Cc: Michal Koutn <mkoutny@suse.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: tejun heo <tj@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Zefan Li <lizefan.x@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Alistair Popple
|
349994cf61 |
mm/rmap: add support for PUD sized mappings to rmap
The rmap doesn't currently support adding a PUD mapping of a folio. This patch adds support for entire PUD mappings of folios, primarily to allow for more standard refcounting of device DAX folios. Currently DAX is the only user of this and it doesn't require support for partially mapped PUD-sized folios so we don't support for that for now. Link: https://lkml.kernel.org/r/248582c07896e30627d1aeaeebc6949cfd91b851.1740713401.git-series.apopple@nvidia.com Signed-off-by: Alistair Popple <apopple@nvidia.com> Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Tested-by: Alison Schofield <alison.schofield@intel.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Asahi Lina <lina@asahilina.net> Cc: Balbir Singh <balbirs@nvidia.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chunyan Zhang <zhang.lyra@gmail.com> Cc: "Darrick J. Wong" <djwong@kernel.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Huacai Chen <chenhuacai@kernel.org> Cc: Ira Weiny <ira.weiny@intel.com> Cc: Jan Kara <jack@suse.cz> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: John Hubbard <jhubbard@nvidia.com> Cc: linmiaohe <linmiaohe@huawei.com> Cc: Logan Gunthorpe <logang@deltatee.com> Cc: Matthew Wilcow (Oracle) <willy@infradead.org> Cc: Michael "Camp Drill Sergeant" Ellerman <mpe@ellerman.id.au> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Xu <peterx@redhat.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Ted Ts'o <tytso@mit.edu> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: WANG Xuerui <kernel@xen0n.name> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Barry Song
|
2f9b43d617 |
mm: avoid splitting pmd for lazyfree pmd-mapped THP in try_to_unmap
The try_to_unmap_one() function currently handles PMD-mapped THPs
inefficiently. It first splits the PMD into PTEs, copies the dirty state
from the PMD to the PTEs, iterates over the PTEs to locate the dirty
state, and then marks the THP as swap-backed. This process involves
unnecessary PMD splitting and redundant iteration. Instead, this
functionality can be efficiently managed in
__discard_anon_folio_pmd_locked(), avoiding the extra steps and improving
performance.
The following microbenchmark redirties folios after invoking MADV_FREE,
then measures the time taken to perform memory reclamation (actually set
those folios swapbacked again) on the redirtied folios.
#include <stdio.h>
#include <sys/mman.h>
#include <string.h>
#include <time.h>
#define SIZE 128*1024*1024 // 128 MB
int main(int argc, char *argv[])
{
while(1) {
volatile int *p = mmap(0, SIZE, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
memset((void *)p, 1, SIZE);
madvise((void *)p, SIZE, MADV_FREE);
/* redirty after MADV_FREE */
memset((void *)p, 1, SIZE);
clock_t start_time = clock();
madvise((void *)p, SIZE, MADV_PAGEOUT);
clock_t end_time = clock();
double elapsed_time = (double)(end_time - start_time) / CLOCKS_PER_SEC;
printf("Time taken by reclamation: %f seconds\n", elapsed_time);
munmap((void *)p, SIZE);
}
return 0;
}
Testing results are as below,
w/o patch:
~ # ./a.out
Time taken by reclamation: 0.007300 seconds
Time taken by reclamation: 0.007226 seconds
Time taken by reclamation: 0.007295 seconds
Time taken by reclamation: 0.007731 seconds
Time taken by reclamation: 0.007134 seconds
Time taken by reclamation: 0.007285 seconds
Time taken by reclamation: 0.007720 seconds
Time taken by reclamation: 0.007128 seconds
Time taken by reclamation: 0.007710 seconds
Time taken by reclamation: 0.007712 seconds
Time taken by reclamation: 0.007236 seconds
Time taken by reclamation: 0.007690 seconds
Time taken by reclamation: 0.007174 seconds
Time taken by reclamation: 0.007670 seconds
Time taken by reclamation: 0.007169 seconds
Time taken by reclamation: 0.007305 seconds
Time taken by reclamation: 0.007432 seconds
Time taken by reclamation: 0.007158 seconds
Time taken by reclamation: 0.007133 seconds
…
w/ patch
~ # ./a.out
Time taken by reclamation: 0.002124 seconds
Time taken by reclamation: 0.002116 seconds
Time taken by reclamation: 0.002150 seconds
Time taken by reclamation: 0.002261 seconds
Time taken by reclamation: 0.002137 seconds
Time taken by reclamation: 0.002173 seconds
Time taken by reclamation: 0.002063 seconds
Time taken by reclamation: 0.002088 seconds
Time taken by reclamation: 0.002169 seconds
Time taken by reclamation: 0.002124 seconds
Time taken by reclamation: 0.002111 seconds
Time taken by reclamation: 0.002224 seconds
Time taken by reclamation: 0.002297 seconds
Time taken by reclamation: 0.002260 seconds
Time taken by reclamation: 0.002246 seconds
Time taken by reclamation: 0.002272 seconds
Time taken by reclamation: 0.002277 seconds
Time taken by reclamation: 0.002462 seconds
…
This patch significantly speeds up try_to_unmap_one() by allowing it
to skip redirtied THPs without splitting the PMD.
Link: https://lkml.kernel.org/r/20250214093015.51024-5-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Suggested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Suggested-by: Lance Yang <ioworker0@gmail.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Lance Yang <ioworker0@gmail.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chis Li <chrisl@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Gavin Shan <gshan@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mauricio Faria de Oliveira <mfo@canonical.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shaoqin Huang <shahuang@redhat.com>
Cc: Tangquan Zheng <zhengtangquan@oppo.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
||
|
Barry Song
|
354dffd295 |
mm: support batched unmap for lazyfree large folios during reclamation
Currently, the PTEs and rmap of a large folio are removed one at a time.
This is not only slow but also causes the large folio to be unnecessarily
added to deferred_split, which can lead to races between the
deferred_split shrinker callback and memory reclamation. This patch
releases all PTEs and rmap entries in a batch. Currently, it only handles
lazyfree large folios.
The below microbench tries to reclaim 128MB lazyfree large folios
whose sizes are 64KiB:
#include <stdio.h>
#include <sys/mman.h>
#include <string.h>
#include <time.h>
#define SIZE 128*1024*1024 // 128 MB
unsigned long read_split_deferred()
{
FILE *file = fopen("/sys/kernel/mm/transparent_hugepage"
"/hugepages-64kB/stats/split_deferred", "r");
if (!file) {
perror("Error opening file");
return 0;
}
unsigned long value;
if (fscanf(file, "%lu", &value) != 1) {
perror("Error reading value");
fclose(file);
return 0;
}
fclose(file);
return value;
}
int main(int argc, char *argv[])
{
while(1) {
volatile int *p = mmap(0, SIZE, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
memset((void *)p, 1, SIZE);
madvise((void *)p, SIZE, MADV_FREE);
clock_t start_time = clock();
unsigned long start_split = read_split_deferred();
madvise((void *)p, SIZE, MADV_PAGEOUT);
clock_t end_time = clock();
unsigned long end_split = read_split_deferred();
double elapsed_time = (double)(end_time - start_time) / CLOCKS_PER_SEC;
printf("Time taken by reclamation: %f seconds, split_deferred: %ld\n",
elapsed_time, end_split - start_split);
munmap((void *)p, SIZE);
}
return 0;
}
w/o patch:
~ # ./a.out
Time taken by reclamation: 0.177418 seconds, split_deferred: 2048
Time taken by reclamation: 0.178348 seconds, split_deferred: 2048
Time taken by reclamation: 0.174525 seconds, split_deferred: 2048
Time taken by reclamation: 0.171620 seconds, split_deferred: 2048
Time taken by reclamation: 0.172241 seconds, split_deferred: 2048
Time taken by reclamation: 0.174003 seconds, split_deferred: 2048
Time taken by reclamation: 0.171058 seconds, split_deferred: 2048
Time taken by reclamation: 0.171993 seconds, split_deferred: 2048
Time taken by reclamation: 0.169829 seconds, split_deferred: 2048
Time taken by reclamation: 0.172895 seconds, split_deferred: 2048
Time taken by reclamation: 0.176063 seconds, split_deferred: 2048
Time taken by reclamation: 0.172568 seconds, split_deferred: 2048
Time taken by reclamation: 0.171185 seconds, split_deferred: 2048
Time taken by reclamation: 0.170632 seconds, split_deferred: 2048
Time taken by reclamation: 0.170208 seconds, split_deferred: 2048
Time taken by reclamation: 0.174192 seconds, split_deferred: 2048
...
w/ patch:
~ # ./a.out
Time taken by reclamation: 0.074231 seconds, split_deferred: 0
Time taken by reclamation: 0.071026 seconds, split_deferred: 0
Time taken by reclamation: 0.072029 seconds, split_deferred: 0
Time taken by reclamation: 0.071873 seconds, split_deferred: 0
Time taken by reclamation: 0.073573 seconds, split_deferred: 0
Time taken by reclamation: 0.071906 seconds, split_deferred: 0
Time taken by reclamation: 0.073604 seconds, split_deferred: 0
Time taken by reclamation: 0.075903 seconds, split_deferred: 0
Time taken by reclamation: 0.073191 seconds, split_deferred: 0
Time taken by reclamation: 0.071228 seconds, split_deferred: 0
Time taken by reclamation: 0.071391 seconds, split_deferred: 0
Time taken by reclamation: 0.071468 seconds, split_deferred: 0
Time taken by reclamation: 0.071896 seconds, split_deferred: 0
Time taken by reclamation: 0.072508 seconds, split_deferred: 0
Time taken by reclamation: 0.071884 seconds, split_deferred: 0
Time taken by reclamation: 0.072433 seconds, split_deferred: 0
Time taken by reclamation: 0.071939 seconds, split_deferred: 0
...
Link: https://lkml.kernel.org/r/20250214093015.51024-4-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chis Li <chrisl@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Gavin Shan <gshan@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mauricio Faria de Oliveira <mfo@canonical.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shaoqin Huang <shahuang@redhat.com>
Cc: Tangquan Zheng <zhengtangquan@oppo.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
||
|
Barry Song
|
2f4ab3ac10 |
mm: support tlbbatch flush for a range of PTEs
This patch lays the groundwork for supporting batch PTE unmapping in try_to_unmap_one(). It introduces range handling for TLB batch flushing, with the range currently set to the size of PAGE_SIZE. The function __flush_tlb_range_nosync() is architecture-specific and is only used within arch/arm64. This function requires the mm structure instead of the vma structure. To allow its reuse by arch_tlbbatch_add_pending(), which operates with mm but not vma, this patch modifies the argument of __flush_tlb_range_nosync() to take mm as its parameter. Link: https://lkml.kernel.org/r/20250214093015.51024-3-21cnbao@gmail.com Signed-off-by: Barry Song <v-songbaohua@oppo.com> Acked-by: Will Deacon <will@kernel.org> Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Shaoqin Huang <shahuang@redhat.com> Cc: Gavin Shan <gshan@redhat.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: David Hildenbrand <david@redhat.com> Cc: Lance Yang <ioworker0@gmail.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Yicong Yang <yangyicong@hisilicon.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Chis Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Kairui Song <kasong@tencent.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Mauricio Faria de Oliveira <mfo@canonical.com> Cc: Tangquan Zheng <zhengtangquan@oppo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Barry Song
|
faeb2831b5 |
mm: set folio swapbacked iff folios are dirty in try_to_unmap_one
Patch series "mm: batched unmap lazyfree large folios during reclamation", v4. Commit |
||
|
Lorenzo Stoakes
|
a4811f53bb |
mm: provide mapping_wrprotect_range() function
In the fb_defio video driver, page dirty state is used to determine when frame buffer pages have been changed, allowing for batched, deferred I/O to be performed for efficiency. This implementation had only one means of doing so effectively - the use of the folio_mkclean() function. However, this use of the function is inappropriate, as the fb_defio implementation allocates kernel memory to back the framebuffer, and then is forced to specified page->index, mapping fields in order to permit the folio_mkclean() rmap traversal to proceed correctly. It is not correct to specify these fields on kernel-allocated memory, and moreover since these are not folios, page->index, mapping are deprecated fields, soon to be removed. We therefore need to provide a means by which we can correctly traverse the reverse mapping and write-protect mappings for a page backing an address_space page cache object at a given offset. This patch provides this - mapping_wrprotect_range() - which allows for this operation to be performed for a specified address_space, offset, PFN and size, without requiring a folio nor, of course, an inappropriate use of page->index, mapping. With this provided, we can subsequently adjust the fb_defio implementation to make use of this function and avoid incorrect invocation of folio_mkclean() and more importantly, incorrect manipulation of page->index and mapping fields. Link: https://lkml.kernel.org/r/e5bf969d64e7f2f2ae944d42341fc8994b736a81.1739029358.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: David Hildenbrand <david@redhat.com> Cc: Helge Deller <deller@gmx.de> Cc: Jaya Kumar <jayakumar.lkml@gmail.com> Cc: Kajtar Zsolt <soci@c64.rulez.org> Cc: Maíra Canal <mcanal@igalia.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Simona Vetter <simona.vetter@ffwll.ch> Cc: Thomas Zimemrmann <tzimmermann@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Lorenzo Stoakes
|
cedae19487 |
mm: refactor rmap_walk_file() to separate out traversal logic
Patch series "expose mapping wrprotect, fix fb_defio use", v3. Right now the only means by which we can write-protect a range using the reverse mapping is via folio_mkclean(). However this is not always the appropriate means of doing so, specifically in the case of the framebuffer deferred I/O logic (fb_defio enabled by CONFIG_FB_DEFERRED_IO). There, kernel pages are mapped read-only and write-protect faults used to batch up I/O operations. Each time the deferred work is done, folio_mkclean() is used to mark the framebuffer page as having had I/O performed on it. However doing so requires the kernel page (perhaps allocated via vmalloc()) to have its page->mapping, index fields set so the rmap can find everything that maps it in order to write-protect. This is problematic as firstly, these fields should not be set for kernel-allocated memory, and secondly these are not folios (it's not user memory) and page->index, mapping fields are now deprecated and soon to be removed. The removal of these fields is imminent, rendering this series more urgent than it might first appear. The implementers cannot be blamed for having used this however, as there is simply no other way of performing this operation correctly. This series fixes this - we provide the mapping_wrprotect_range() function to allow the reverse mapping to be used to look up mappings from the page cache object (i.e. its address_space pointer) at a specific offset. The fb_defio logic already stores this offset, and can simply be expanded to keep track of the page cache object, so the change then becomes straight-forward. This series should have no functional change. This patch (of 3): In order to permit the traversal of the reverse mapping at a specified mapping and offset rather than those specified by an input folio, we need to separate out the portion of the rmap file logic which deals with this traversal from those parts of the logic which interact with the folio. This patch achieves this by adding a new static __rmap_walk_file() function which rmap_walk_file() invokes. This function permits the ability to pass NULL folio, on the assumption that the caller has provided for this correctly in the callbacks specified in the rmap_walk_control object. Though it provides for this, and adds debug asserts to ensure that, should a folio be specified, these are equal to the mapping and offset specified in the folio, there should be no functional change as a result of this patch. The reason for adding this is to enable for future changes to permit users to be able to traverse mappings of userland-mapped kernel memory, write-protecting those mappings to enable page_mkwrite() or pfn_mkwrite() fault handlers to be retriggered on subsequent dirty. Link: https://lkml.kernel.org/r/cover.1739029358.git.lorenzo.stoakes@oracle.com Link: https://lkml.kernel.org/r/0d1acec0cba1e5a12f9b53efcabc397541c90517.1739029358.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: David Hildenbrand <david@redhat.com> Cc: Helge Deller <deller@gmx.de> Cc: Jaya Kumar <jayakumar.lkml@gmail.com> Cc: Kajtar Zsolt <soci@c64.rulez.org> Cc: Maíra Canal <mcanal@igalia.com> Cc: Matthew Wilcox <willy@infradead.org> [English fixes] Cc: Simona Vetter <simona.vetter@ffwll.ch> Cc: Thomas Zimemrmann <tzimmermann@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
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b8932ca8b9 |
mm/rmap: avoid -EBUSY from make_device_exclusive()
Failing to obtain the folio lock, for example because the folio is concurrently getting migrated or swapped out, can easily make the callers fail: for example, the hmm selftest can sometimes be observed to fail because of this. Instead of forcing the caller to retry, let's simply retry in this to-be-expected case. Similarly, avoid spurious failures simply because we raced with someone (e.g., swapout) modifying the page table such that our folio_walk fails. Simply unconditionally lock the folio, and retry GUP if our folio_walk fails. Note that the folio_walk repeatedly failing is not something we expect. Note that we might want to avoid grabbing the folio lock at some point; for now, keep that as is and only unconditionally lock the folio. With this change, the hmm selftests don't fail simply because the folio is already locked. While this fixes the selftests in some cases, it's likely not something that deserves a "Fixes:". Link: https://lkml.kernel.org/r/20250210193801.781278-18-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Tested-by: Alistair Popple <apopple@nvidia.com> Cc: Alex Shi <alexs@kernel.org> Cc: Danilo Krummrich <dakr@kernel.org> Cc: Dave Airlie <airlied@gmail.com> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Karol Herbst <kherbst@redhat.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Lyude <lyude@redhat.com> Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: SeongJae Park <sj@kernel.org> Cc: Simona Vetter <simona.vetter@ffwll.ch> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Yanteng Si <si.yanteng@linux.dev> Cc: Barry Song <v-songbaohua@oppo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
|
f495bd7e0d |
mm/rmap: keep mapcount untouched for device-exclusive entries
Now that conversion to device-exclusive does no longer perform an rmap
walk and all page_vma_mapped_walk() users were taught to properly handle
device-exclusive entries, let's treat device-exclusive entries just as if
they would be present, similar to how we handle device-private entries
already.
This fixes swapout/migration/split/hwpoison of folios with
device-exclusive entries.
We only had to take care of page_vma_mapped_walk() users, because these
traditionally assume pte_present(). Other page table walkers already have
to handle !pte_present(), and some of them might simply skip them (e.g.,
MADV_PAGEOUT) if they are not specialized on them. This change doesn't
modify the latter.
Note that while folios with device-exclusive PTEs can now get migrated,
khugepaged will not collapse a THP if there is device-exclusive PTE.
Doing so might also not be desired if the device frequently performs
atomics to the same page. Similarly, KSM will never merge order-0 folios
that are device-exclusive.
Link: https://lkml.kernel.org/r/20250210193801.781278-17-david@redhat.com
Fixes:
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David Hildenbrand
|
bd1f2b2ace |
mm/rmap: handle device-exclusive entries correctly in page_vma_mkclean_one()
Ever since commit |
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David Hildenbrand
|
bf983108be |
mm/rmap: handle device-exclusive entries correctly in try_to_migrate_one()
Ever since commit |
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David Hildenbrand
|
6552929560 |
mm/rmap: handle device-exclusive entries correctly in try_to_unmap_one()
Ever since commit |
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David Hildenbrand
|
c25465eb76 |
mm: use single SWP_DEVICE_EXCLUSIVE entry type
There is no need for the distinction anymore; let's merge the readable and writable device-exclusive entries into a single device-exclusive entry type. Link: https://lkml.kernel.org/r/20250210193801.781278-7-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Acked-by: Simona Vetter <simona.vetter@ffwll.ch> Reviewed-by: Alistair Popple <apopple@nvidia.com> Tested-by: Alistair Popple <apopple@nvidia.com> Cc: Alex Shi <alexs@kernel.org> Cc: Danilo Krummrich <dakr@kernel.org> Cc: Dave Airlie <airlied@gmail.com> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Karol Herbst <kherbst@redhat.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Lyude <lyude@redhat.com> Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: SeongJae Park <sj@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Yanteng Si <si.yanteng@linux.dev> Cc: Barry Song <v-songbaohua@oppo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
|
438354724f |
mm/rmap: implement make_device_exclusive() using folio_walk instead of rmap walk
We require a writable PTE and only support anonymous folio: we can only have exactly one PTE pointing at that page, which we can just lookup using a folio walk, avoiding the rmap walk and the anon VMA lock. So let's stop doing an rmap walk and perform a folio walk instead, so we can easily just modify a single PTE and avoid relying on rmap/mapcounts. We now effectively work on a single PTE instead of multiple PTEs of a large folio, allowing for conversion of individual PTEs from non-exclusive to device-exclusive -- note that the opposite direction always works on single PTEs: restore_exclusive_pte(). With this change, device-exclusive handling is fully compatible with THPs / large folios. We still require PMD-sized THPs to get PTE-mapped, and supporting PMD-mapped THP (without the PTE-remapping) is a different endeavour that might not be worth it at this point: it might even have negative side-effects [1]. This gets rid of the "folio_mapcount()" usage and let's us fix ordinary rmap walks (migration/swapout) next. Spell out that messing with the mapcount is wrong and must be fixed. [1] https://lkml.kernel.org/r/Z5tI-cOSyzdLjoe_@phenom.ffwll.local Link: https://lkml.kernel.org/r/20250210193801.781278-5-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Tested-by: Alistair Popple <apopple@nvidia.com> Cc: Alex Shi <alexs@kernel.org> Cc: Danilo Krummrich <dakr@kernel.org> Cc: Dave Airlie <airlied@gmail.com> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Karol Herbst <kherbst@redhat.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Lyude <lyude@redhat.com> Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: SeongJae Park <sj@kernel.org> Cc: Simona Vetter <simona.vetter@ffwll.ch> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Yanteng Si <si.yanteng@linux.dev> Cc: Barry Song <v-songbaohua@oppo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
|
599b684a78 |
mm/rmap: convert make_device_exclusive_range() to make_device_exclusive()
The single "real" user in the tree of make_device_exclusive_range() always requests making only a single address exclusive. The current implementation is hard to fix for properly supporting anonymous THP / large folios and for avoiding messing with rmap walks in weird ways. So let's always process a single address/page and return folio + page to minimize page -> folio lookups. This is a preparation for further changes. Reject any non-anonymous or hugetlb folios early, directly after GUP. While at it, extend the documentation of make_device_exclusive() to clarify some things. Link: https://lkml.kernel.org/r/20250210193801.781278-4-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Acked-by: Simona Vetter <simona.vetter@ffwll.ch> Reviewed-by: Alistair Popple <apopple@nvidia.com> Tested-by: Alistair Popple <apopple@nvidia.com> Cc: Alex Shi <alexs@kernel.org> Cc: Danilo Krummrich <dakr@kernel.org> Cc: Dave Airlie <airlied@gmail.com> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Karol Herbst <kherbst@redhat.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Lyude <lyude@redhat.com> Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: SeongJae Park <sj@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Yanteng Si <si.yanteng@linux.dev> Cc: Barry Song <v-songbaohua@oppo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
|
bc3fe6805c |
mm/rmap: reject hugetlb folios in folio_make_device_exclusive()
Even though FOLL_SPLIT_PMD on hugetlb now always fails with -EOPNOTSUPP, let's add a safety net in case FOLL_SPLIT_PMD usage would ever be reworked. In particular, before commit |
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Matthew Wilcox (Oracle)
|
68158bfa3d |
mm: mass constification of folio/page pointers
Now that page_pgoff() takes const pointers, we can constify the pointers to a lot of functions. Link: https://lkml.kernel.org/r/20241005200121.3231142-5-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Matthew Wilcox (Oracle)
|
713da0b33b |
mm: renovate page_address_in_vma()
This function doesn't modify any of its arguments, so if we make a few other functions take const pointers, we can make page_address_in_vma() take const pointers too. All of its callers have the containing folio already, so pass that in as an argument instead of recalculating it. Also add kernel-doc Link: https://lkml.kernel.org/r/20241005200121.3231142-4-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Matthew Wilcox (Oracle)
|
7d3e93eca3 |
mm: use page_pgoff() in more places
There are several places which currently open-code page_pgoff(), convert them to call it. Link: https://lkml.kernel.org/r/20241005200121.3231142-3-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Matthew Wilcox (Oracle)
|
f7470591f8 |
mm: convert page_to_pgoff() to page_pgoff()
Patch series "page->index removals in mm", v2. As part of shrinking struct page, we need to stop using page->index. This patchset gets rid of most of the remaining references to page->index in mm, as well as increasing the number of functions which take a const folio/page pointer. It shrinks the text segment of mm by a few hundred bytes in my test config, probably mostly from removing calls to compound_head() in page_to_pgoff(). This patch (of 7): Change the function signature to pass in the folio as all three callers have it. This removes a reference to page->index, which we're trying to get rid of. And add kernel-doc. Link: https://lkml.kernel.org/r/20241005200121.3231142-1-willy@infradead.org Link: https://lkml.kernel.org/r/20241005200121.3231142-2-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Shakeel Butt
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a29c0e4b2e |
memcg-v1: remove memcg move locking code
The memcg v1's charge move feature has been deprecated. All the places using the memcg move lock, have stopped using it as they don't need the protection any more. Let's proceed to remove all the locking code related to charge moving. Link: https://lkml.kernel.org/r/20241025012304.2473312-7-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> Acked-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Hugh Dickins <hughd@google.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Yu Zhao
|
1d4832becd |
mm: multi-gen LRU: use {ptep,pmdp}_clear_young_notify()
When the MM_WALK capability is enabled, memory that is mostly accessed by
a VM appears younger than it really is, therefore this memory will be less
likely to be evicted. Therefore, the presence of a running VM can
significantly increase swap-outs for non-VM memory, regressing the
performance for the rest of the system.
Fix this regression by always calling {ptep,pmdp}_clear_young_notify()
whenever we clear the young bits on PMDs/PTEs.
[jthoughton@google.com: fix link-time error]
Link: https://lkml.kernel.org/r/20241019012940.3656292-3-jthoughton@google.com
Fixes:
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Usama Arif
|
8422acdc97 |
mm: introduce a pageflag for partially mapped folios
Currently folio->_deferred_list is used to keep track of partially_mapped folios that are going to be split under memory pressure. In the next patch, all THPs that are faulted in and collapsed by khugepaged are also going to be tracked using _deferred_list. This patch introduces a pageflag to be able to distinguish between partially mapped folios and others in the deferred_list at split time in deferred_split_scan. Its needed as __folio_remove_rmap decrements _mapcount, _large_mapcount and _entire_mapcount, hence it won't be possible to distinguish between partially mapped folios and others in deferred_split_scan. Eventhough it introduces an extra flag to track if the folio is partially mapped, there is no functional change intended with this patch and the flag is not useful in this patch itself, it will become useful in the next patch when _deferred_list has non partially mapped folios. Link: https://lkml.kernel.org/r/20240830100438.3623486-5-usamaarif642@gmail.com Signed-off-by: Usama Arif <usamaarif642@gmail.com> Cc: Alexander Zhu <alexlzhu@fb.com> Cc: Barry Song <baohua@kernel.org> Cc: David Hildenbrand <david@redhat.com> Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Kairui Song <ryncsn@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mike Rapoport <rppt@kernel.org> Cc: Nico Pache <npache@redhat.com> Cc: Rik van Riel <riel@surriel.com> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Shakeel Butt <shakeel.butt@linux.dev> Cc: Shuang Zhai <zhais@google.com> Cc: Yu Zhao <yuzhao@google.com> Cc: Shuang Zhai <szhai2@cs.rochester.edu> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Barry Song
|
5d65c8d758 |
mm: count the number of anonymous THPs per size
Patch series "mm: count the number of anonymous THPs per size", v4.
Knowing the number of transparent anon THPs in the system is crucial
for performance analysis. It helps in understanding the ratio and
distribution of THPs versus small folios throughout the system.
Additionally, partial unmapping by userspace can lead to significant waste
of THPs over time and increase memory reclamation pressure. We need this
information for comprehensive system tuning.
This patch (of 2):
Let's track for each anonymous THP size, how many of them are currently
allocated. We'll track the complete lifespan of an anon THP, starting
when it becomes an anon THP ("large anon folio") (->mapping gets set),
until it gets freed (->mapping gets cleared).
Introduce a new "nr_anon" counter per THP size and adjust the
corresponding counter in the following cases:
* We allocate a new THP and call folio_add_new_anon_rmap() to map
it the first time and turn it into an anon THP.
* We split an anon THP into multiple smaller ones.
* We migrate an anon THP, when we prepare the destination.
* We free an anon THP back to the buddy.
Note that AnonPages in /proc/meminfo currently tracks the total number of
*mapped* anonymous *pages*, and therefore has slightly different
semantics. In the future, we might also want to track "nr_anon_mapped"
for each THP size, which might be helpful when comparing it to the number
of allocated anon THPs (long-term pinning, stuck in swapcache, memory
leaks, ...).
Further note that for now, we only track anon THPs after they got their
->mapping set, for example via folio_add_new_anon_rmap(). If we would
allocate some in the swapcache, they will only show up in the statistics
for now after they have been mapped to user space the first time, where we
call folio_add_new_anon_rmap().
[akpm@linux-foundation.org: documentation fixups, per David]
Link: https://lkml.kernel.org/r/3e8add35-e26b-443b-8a04-1078f4bc78f6@redhat.com
Link: https://lkml.kernel.org/r/20240824010441.21308-1-21cnbao@gmail.com
Link: https://lkml.kernel.org/r/20240824010441.21308-2-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Chuanhua Han <hanchuanhua@oppo.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuai Yuan <yuanshuai@oppo.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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David Hildenbrand
|
d0b003ce97 |
mm/rmap: use folio->_mapcount for small folios
We have some cases left whereby we operate on small folios and still refer to page->_mapcount. Let's just use folio->_mapcount instead, which currently still overlays page->_mapcount, so no change. This change will make it easier to later spot any remaining users of page->_mapcount that target tail pages. Link: https://lkml.kernel.org/r/20240816103246.719209-1-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
|
43c9074e6f |
mm/rmap: minimize folio->_nr_pages_mapped updates when batching PTE (un)mapping
It is not immediately obvious, but we can move the folio->_nr_pages_mapped update out of the loop and reduce the number of atomic ops without affecting the stats. The important point to realize is that only removing the last PMD mapping will result in _nr_pages_mapped going below ENTIRELY_MAPPED, not the individual atomic_inc_return_relaxed() calls. Concurrent races with removal of PMD mappings should be handled as expected, just like when we would have such races right now on a single mapcount update. In a simple munmap() microbenchmark [1] on 1 GiB of memory backed by the same PTE-mapped folio size (only mapped by a single process such that they will get completely unmapped), this change results in a speedup (positive is good) per folio size on a x86-64 Intel machine of roughly (a bit of noise expected): * 16 KiB: +10% * 32 KiB: +15% * 64 KiB: +17% * 128 KiB: +21% * 256 KiB: +22% * 512 KiB: +22% * 1024 KiB: +23% * 2048 KiB: +27% [1] https://gitlab.com/davidhildenbrand/scratchspace/-/blob/main/pte-mapped-folio-benchmarks.c Link: https://lkml.kernel.org/r/20240807115515.1640951-1-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
|
6654d28995 |
mm/rmap: cleanup partially-mapped handling in __folio_remove_rmap()
Let's simplify and reduce code indentation. In the RMAP_LEVEL_PTE case, we already check for nr when computing partially_mapped. For RMAP_LEVEL_PMD, it's a bit more confusing. Likely, we don't need the "nr" check, but we could have "nr < nr_pmdmapped" also if we stumbled into the "/* Raced ahead of another remove and an add? */" case. So let's simply move the nr check in there. Note that partially_mapped is always false for small folios. No functional change intended. Link: https://lkml.kernel.org/r/20240710214350.147864-1-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Zi Yan <ziy@nvidia.com> Reviewed-by: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Zhiguo Jiang
|
c495b97624 |
mm: shrink skip folio mapped by an exiting process
The releasing process of the non-shared anonymous folio mapped solely by an exiting process may go through two flows: 1) the anonymous folio is firstly is swaped-out into swapspace and transformed into a swp_entry in shrink_folio_list; 2) then the swp_entry is released in the process exiting flow. This will result in the high cpu load of releasing a non-shared anonymous folio mapped solely by an exiting process. When the low system memory and the exiting process exist at the same time, it will be likely to happen, because the non-shared anonymous folio mapped solely by an exiting process may be reclaimed by shrink_folio_list. This patch is that shrink skips the non-shared anonymous folio solely mapped by an exting process and this folio is only released directly in the process exiting flow, which will save swap-out time and alleviate the load of the process exiting. Barry provided some effectiveness testing in [1]. "I observed that this patch effectively skipped 6114 folios (either 4KB or 64KB mTHP), potentially reducing the swap-out by up to 92MB (97,300,480 bytes) during the process exit. The working set size is 256MB." Link: https://lkml.kernel.org/r/20240710083641.546-1-justinjiang@vivo.com Link: https://lore.kernel.org/linux-mm/20240710033212.36497-1-21cnbao@gmail.com/ [1] Signed-off-by: Zhiguo Jiang <justinjiang@vivo.com> Acked-by: Barry Song <baohua@kernel.org> Cc: David Hildenbrand <david@redhat.com> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Linus Torvalds
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7a3fad30fd |
Random number generator updates for Linux 6.11-rc1.
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Jason A. Donenfeld
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9651fcedf7 |
mm: add MAP_DROPPABLE for designating always lazily freeable mappings
The vDSO getrandom() implementation works with a buffer allocated with a
new system call that has certain requirements:
- It shouldn't be written to core dumps.
* Easy: VM_DONTDUMP.
- It should be zeroed on fork.
* Easy: VM_WIPEONFORK.
- It shouldn't be written to swap.
* Uh-oh: mlock is rlimited.
* Uh-oh: mlock isn't inherited by forks.
- It shouldn't reserve actual memory, but it also shouldn't crash when
page faulting in memory if none is available
* Uh-oh: VM_NORESERVE means segfaults.
It turns out that the vDSO getrandom() function has three really nice
characteristics that we can exploit to solve this problem:
1) Due to being wiped during fork(), the vDSO code is already robust to
having the contents of the pages it reads zeroed out midway through
the function's execution.
2) In the absolute worst case of whatever contingency we're coding for,
we have the option to fallback to the getrandom() syscall, and
everything is fine.
3) The buffers the function uses are only ever useful for a maximum of
60 seconds -- a sort of cache, rather than a long term allocation.
These characteristics mean that we can introduce VM_DROPPABLE, which
has the following semantics:
a) It never is written out to swap.
b) Under memory pressure, mm can just drop the pages (so that they're
zero when read back again).
c) It is inherited by fork.
d) It doesn't count against the mlock budget, since nothing is locked.
e) If there's not enough memory to service a page fault, it's not fatal,
and no signal is sent.
This way, allocations used by vDSO getrandom() can use:
VM_DROPPABLE | VM_DONTDUMP | VM_WIPEONFORK | VM_NORESERVE
And there will be no problem with OOMing, crashing on overcommitment,
using memory when not in use, not wiping on fork(), coredumps, or
writing out to swap.
In order to let vDSO getrandom() use this, expose these via mmap(2) as
MAP_DROPPABLE.
Note that this involves removing the MADV_FREE special case from
sort_folio(), which according to Yu Zhao is unnecessary and will simply
result in an extra call to shrink_folio_list() in the worst case. The
chunk removed reenables the swapbacked flag, which we don't want for
VM_DROPPABLE, and we can't conditionalize it here because there isn't a
vma reference available.
Finally, the provided self test ensures that this is working as desired.
Cc: linux-mm@kvack.org
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Barry Song
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4c1171f1d2 |
mm: remove folio_test_anon(folio)==false path in __folio_add_anon_rmap()
The folio_test_anon(folio)==false cases has been relocated to
folio_add_new_anon_rmap(). Additionally, four other callers consistently
pass anonymous folios.
stack 1:
remove_migration_pmd
-> folio_add_anon_rmap_pmd
-> __folio_add_anon_rmap
stack 2:
__split_huge_pmd_locked
-> folio_add_anon_rmap_ptes
-> __folio_add_anon_rmap
stack 3:
remove_migration_pmd
-> folio_add_anon_rmap_pmd
-> __folio_add_anon_rmap (RMAP_LEVEL_PMD)
stack 4:
try_to_merge_one_page
-> replace_page
-> folio_add_anon_rmap_pte
-> __folio_add_anon_rmap
__folio_add_anon_rmap() only needs to handle the cases
folio_test_anon(folio)==true now.
We can remove the !folio_test_anon(folio)) path within
__folio_add_anon_rmap() now.
Link: https://lkml.kernel.org/r/20240617231137.80726-4-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Tested-by: Shuai Yuan <yuanshuai@oppo.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Barry Song
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9ae2feaced |
mm: use folio_add_new_anon_rmap() if folio_test_anon(folio)==false
For the !folio_test_anon(folio) case, we can now invoke
folio_add_new_anon_rmap() with the rmap flags set to either EXCLUSIVE or
non-EXCLUSIVE. This action will suppress the VM_WARN_ON_FOLIO check
within __folio_add_anon_rmap() while initiating the process of bringing up
mTHP swapin.
static __always_inline void __folio_add_anon_rmap(struct folio *folio,
struct page *page, int nr_pages, struct vm_area_struct *vma,
unsigned long address, rmap_t flags, enum rmap_level level)
{
...
if (unlikely(!folio_test_anon(folio))) {
VM_WARN_ON_FOLIO(folio_test_large(folio) &&
level != RMAP_LEVEL_PMD, folio);
}
...
}
It also improves the code's readability. Currently, all new anonymous
folios calling folio_add_anon_rmap_ptes() are order-0. This ensures that
new folios cannot be partially exclusive; they are either entirely
exclusive or entirely shared.
A useful comment from Hugh's fix:
: Commit "mm: use folio_add_new_anon_rmap() if folio_test_anon(folio)==
: false" has extended folio_add_new_anon_rmap() to use on non-exclusive
: folios, already visible to others in swap cache and on LRU.
:
: That renders its non-atomic __folio_set_swapbacked() unsafe: it risks
: overwriting concurrent atomic operations on folio->flags, losing bits
: added or restoring bits cleared. Since it's only used in this risky way
: when folio_test_locked and !folio_test_anon, many such races are excluded;
: but, for example, isolations by folio_test_clear_lru() are vulnerable, and
: setting or clearing active.
:
: It could just use the atomic folio_set_swapbacked(); but this function
: does try to avoid atomics where it can, so use a branch instead: just
: avoid setting swapbacked when it is already set, that is good enough.
: (Swapbacked is normally stable once set: lazyfree can undo it, but only
: later, when found anon in a page table.)
:
: This fixes a lot of instability under compaction and swapping loads:
: assorted "Bad page"s, VM_BUG_ON_FOLIO()s, apparently even page double
: frees - though I've not worked out what races could lead to the latter.
[akpm@linux-foundation.org: comment fixes, per David and akpm]
[v-songbaohua@oppo.com: lock the folio to avoid race]
Link: https://lkml.kernel.org/r/20240622032002.53033-1-21cnbao@gmail.com
[hughd@google.com: folio_add_new_anon_rmap() careful __folio_set_swapbacked()]
Link: https://lkml.kernel.org/r/f3599b1d-8323-0dc5-e9e0-fdb3cfc3dd5a@google.com
Link: https://lkml.kernel.org/r/20240617231137.80726-3-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Tested-by: Shuai Yuan <yuanshuai@oppo.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Barry Song
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15bde4abab |
mm: extend rmap flags arguments for folio_add_new_anon_rmap
Patch series "mm: clarify folio_add_new_anon_rmap() and __folio_add_anon_rmap()", v2. This patchset is preparatory work for mTHP swapin. folio_add_new_anon_rmap() assumes that new anon rmaps are always exclusive. However, this assumption doesn’t hold true for cases like do_swap_page(), where a new anon might be added to the swapcache and is not necessarily exclusive. The patchset extends the rmap flags to allow folio_add_new_anon_rmap() to handle both exclusive and non-exclusive new anon folios. The do_swap_page() function is updated to use this extended API with rmap flags. Consequently, all new anon folios now consistently use folio_add_new_anon_rmap(). The special case for !folio_test_anon() in __folio_add_anon_rmap() can be safely removed. In conclusion, new anon folios always use folio_add_new_anon_rmap(), regardless of exclusivity. Old anon folios continue to use __folio_add_anon_rmap() via folio_add_anon_rmap_pmd() and folio_add_anon_rmap_ptes(). This patch (of 3): In the case of a swap-in, a new anonymous folio is not necessarily exclusive. This patch updates the rmap flags to allow a new anonymous folio to be treated as either exclusive or non-exclusive. To maintain the existing behavior, we always use EXCLUSIVE as the default setting. [akpm@linux-foundation.org: cleanup and constifications per David and akpm] [v-songbaohua@oppo.com: fix missing doc for flags of folio_add_new_anon_rmap()] Link: https://lkml.kernel.org/r/20240619210641.62542-1-21cnbao@gmail.com [v-songbaohua@oppo.com: enhance doc for extend rmap flags arguments for folio_add_new_anon_rmap] Link: https://lkml.kernel.org/r/20240622030256.43775-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240617231137.80726-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240617231137.80726-2-21cnbao@gmail.com Signed-off-by: Barry Song <v-songbaohua@oppo.com> Suggested-by: David Hildenbrand <david@redhat.com> Tested-by: Shuai Yuan <yuanshuai@oppo.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Chris Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Yang Shi <shy828301@gmail.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Yu Zhao <yuzhao@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |