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https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
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08e552c69c
A big patch for changing memcg's LRU semantics.
Now,
- page_cgroup is linked to mem_cgroup's its own LRU (per zone).
- LRU of page_cgroup is not synchronous with global LRU.
- page and page_cgroup is one-to-one and statically allocated.
- To find page_cgroup is on what LRU, you have to check pc->mem_cgroup as
- lru = page_cgroup_zoneinfo(pc, nid_of_pc, zid_of_pc);
- SwapCache is handled.
And, when we handle LRU list of page_cgroup, we do following.
pc = lookup_page_cgroup(page);
lock_page_cgroup(pc); .....................(1)
mz = page_cgroup_zoneinfo(pc);
spin_lock(&mz->lru_lock);
.....add to LRU
spin_unlock(&mz->lru_lock);
unlock_page_cgroup(pc);
But (1) is spin_lock and we have to be afraid of dead-lock with zone->lru_lock.
So, trylock() is used at (1), now. Without (1), we can't trust "mz" is correct.
This is a trial to remove this dirty nesting of locks.
This patch changes mz->lru_lock to be zone->lru_lock.
Then, above sequence will be written as
spin_lock(&zone->lru_lock); # in vmscan.c or swap.c via global LRU
mem_cgroup_add/remove/etc_lru() {
pc = lookup_page_cgroup(page);
mz = page_cgroup_zoneinfo(pc);
if (PageCgroupUsed(pc)) {
....add to LRU
}
spin_lock(&zone->lru_lock); # in vmscan.c or swap.c via global LRU
This is much simpler.
(*) We're safe even if we don't take lock_page_cgroup(pc). Because..
1. When pc->mem_cgroup can be modified.
- at charge.
- at account_move().
2. at charge
the PCG_USED bit is not set before pc->mem_cgroup is fixed.
3. at account_move()
the page is isolated and not on LRU.
Pros.
- easy for maintenance.
- memcg can make use of laziness of pagevec.
- we don't have to duplicated LRU/Active/Unevictable bit in page_cgroup.
- LRU status of memcg will be synchronized with global LRU's one.
- # of locks are reduced.
- account_move() is simplified very much.
Cons.
- may increase cost of LRU rotation.
(no impact if memcg is not configured.)
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
127 lines
2.9 KiB
C
127 lines
2.9 KiB
C
#ifndef __LINUX_PAGE_CGROUP_H
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#define __LINUX_PAGE_CGROUP_H
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#ifdef CONFIG_CGROUP_MEM_RES_CTLR
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#include <linux/bit_spinlock.h>
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/*
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* Page Cgroup can be considered as an extended mem_map.
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* A page_cgroup page is associated with every page descriptor. The
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* page_cgroup helps us identify information about the cgroup
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* All page cgroups are allocated at boot or memory hotplug event,
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* then the page cgroup for pfn always exists.
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*/
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struct page_cgroup {
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unsigned long flags;
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struct mem_cgroup *mem_cgroup;
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struct page *page;
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struct list_head lru; /* per cgroup LRU list */
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};
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void __meminit pgdat_page_cgroup_init(struct pglist_data *pgdat);
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void __init page_cgroup_init(void);
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struct page_cgroup *lookup_page_cgroup(struct page *page);
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enum {
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/* flags for mem_cgroup */
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PCG_LOCK, /* page cgroup is locked */
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PCG_CACHE, /* charged as cache */
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PCG_USED, /* this object is in use. */
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};
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#define TESTPCGFLAG(uname, lname) \
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static inline int PageCgroup##uname(struct page_cgroup *pc) \
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{ return test_bit(PCG_##lname, &pc->flags); }
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#define SETPCGFLAG(uname, lname) \
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static inline void SetPageCgroup##uname(struct page_cgroup *pc)\
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{ set_bit(PCG_##lname, &pc->flags); }
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#define CLEARPCGFLAG(uname, lname) \
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static inline void ClearPageCgroup##uname(struct page_cgroup *pc) \
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{ clear_bit(PCG_##lname, &pc->flags); }
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/* Cache flag is set only once (at allocation) */
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TESTPCGFLAG(Cache, CACHE)
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TESTPCGFLAG(Used, USED)
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CLEARPCGFLAG(Used, USED)
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static inline int page_cgroup_nid(struct page_cgroup *pc)
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{
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return page_to_nid(pc->page);
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}
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static inline enum zone_type page_cgroup_zid(struct page_cgroup *pc)
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{
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return page_zonenum(pc->page);
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}
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static inline void lock_page_cgroup(struct page_cgroup *pc)
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{
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bit_spin_lock(PCG_LOCK, &pc->flags);
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}
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static inline int trylock_page_cgroup(struct page_cgroup *pc)
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{
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return bit_spin_trylock(PCG_LOCK, &pc->flags);
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}
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static inline void unlock_page_cgroup(struct page_cgroup *pc)
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{
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bit_spin_unlock(PCG_LOCK, &pc->flags);
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}
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#else /* CONFIG_CGROUP_MEM_RES_CTLR */
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struct page_cgroup;
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static inline void __meminit pgdat_page_cgroup_init(struct pglist_data *pgdat)
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{
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}
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static inline struct page_cgroup *lookup_page_cgroup(struct page *page)
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{
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return NULL;
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}
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static inline void page_cgroup_init(void)
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{
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}
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#endif
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#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
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#include <linux/swap.h>
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extern struct mem_cgroup *
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swap_cgroup_record(swp_entry_t ent, struct mem_cgroup *mem);
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extern struct mem_cgroup *lookup_swap_cgroup(swp_entry_t ent);
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extern int swap_cgroup_swapon(int type, unsigned long max_pages);
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extern void swap_cgroup_swapoff(int type);
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#else
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#include <linux/swap.h>
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static inline
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struct mem_cgroup *swap_cgroup_record(swp_entry_t ent, struct mem_cgroup *mem)
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{
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return NULL;
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}
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static inline
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struct mem_cgroup *lookup_swap_cgroup(swp_entry_t ent)
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{
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return NULL;
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}
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static inline int
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swap_cgroup_swapon(int type, unsigned long max_pages)
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{
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return 0;
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}
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static inline void swap_cgroup_swapoff(int type)
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{
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return;
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}
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#endif
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#endif
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