From b16e096198ba9e530c9fd3a955cde66b6a5efc8e Mon Sep 17 00:00:00 2001 From: Alexander Motin Date: Mon, 4 Nov 2024 19:42:06 -0500 Subject: [PATCH] Reduce dirty records memory usage Small block workloads may use a very large number of dirty records. During simple block cloning test due to BRT still using 4KB blocks I can easily see up to 2.5M of those used. Before this change dbuf_dirty_record_t structures representing them were allocated via kmem_zalloc(), that rounded their size up to 512 bytes. Introduction of specialized kmem cache allows to reduce the size from 512 to 408 bytes. Additionally, since override and raw params in dirty records are mutually exclusive, puting them into a union allows to reduce structure size down to 368 bytes, increasing the saving to 28%, that can be a 0.5GB or more of RAM. Reviewed-by: Brian Behlendorf Reviewed-by: Brian Atkinson Signed-off-by: Alexander Motin Sponsored by: iXsystems, Inc. Closes #16694 --- include/sys/dbuf.h | 26 +++++++++++++++++--------- module/zfs/dbuf.c | 21 ++++++++++++++++----- module/zfs/dmu.c | 9 ++++----- module/zfs/dmu_direct.c | 1 + module/zfs/dnode_sync.c | 2 +- 5 files changed, 39 insertions(+), 20 deletions(-) diff --git a/include/sys/dbuf.h b/include/sys/dbuf.h index c9bfb9a80..e69464809 100644 --- a/include/sys/dbuf.h +++ b/include/sys/dbuf.h @@ -171,7 +171,6 @@ typedef struct dbuf_dirty_record { * gets COW'd in a subsequent transaction group. */ arc_buf_t *dr_data; - blkptr_t dr_overridden_by; override_states_t dr_override_state; uint8_t dr_copies; boolean_t dr_nopwrite; @@ -179,14 +178,21 @@ typedef struct dbuf_dirty_record { boolean_t dr_diowrite; boolean_t dr_has_raw_params; - /* - * If dr_has_raw_params is set, the following crypt - * params will be set on the BP that's written. - */ - boolean_t dr_byteorder; - uint8_t dr_salt[ZIO_DATA_SALT_LEN]; - uint8_t dr_iv[ZIO_DATA_IV_LEN]; - uint8_t dr_mac[ZIO_DATA_MAC_LEN]; + /* Override and raw params are mutually exclusive. */ + union { + blkptr_t dr_overridden_by; + struct { + /* + * If dr_has_raw_params is set, the + * following crypt params will be set + * on the BP that's written. + */ + boolean_t dr_byteorder; + uint8_t dr_salt[ZIO_DATA_SALT_LEN]; + uint8_t dr_iv[ZIO_DATA_IV_LEN]; + uint8_t dr_mac[ZIO_DATA_MAC_LEN]; + }; + }; } dl; struct dirty_lightweight_leaf { /* @@ -346,6 +352,8 @@ typedef struct dbuf_hash_table { typedef void (*dbuf_prefetch_fn)(void *, uint64_t, uint64_t, boolean_t); +extern kmem_cache_t *dbuf_dirty_kmem_cache; + uint64_t dbuf_whichblock(const struct dnode *di, const int64_t level, const uint64_t offset); diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c index df9368fc8..b1419d96f 100644 --- a/module/zfs/dbuf.c +++ b/module/zfs/dbuf.c @@ -182,6 +182,7 @@ static void dbuf_sync_leaf_verify_bonus_dnode(dbuf_dirty_record_t *dr); * Global data structures and functions for the dbuf cache. */ static kmem_cache_t *dbuf_kmem_cache; +kmem_cache_t *dbuf_dirty_kmem_cache; static taskq_t *dbu_evict_taskq; static kthread_t *dbuf_cache_evict_thread; @@ -966,6 +967,8 @@ dbuf_init(void) dbuf_kmem_cache = kmem_cache_create("dmu_buf_impl_t", sizeof (dmu_buf_impl_t), 0, dbuf_cons, dbuf_dest, NULL, NULL, NULL, 0); + dbuf_dirty_kmem_cache = kmem_cache_create("dbuf_dirty_record_t", + sizeof (dbuf_dirty_record_t), 0, NULL, NULL, NULL, NULL, NULL, 0); for (int i = 0; i < hmsize; i++) mutex_init(&h->hash_mutexes[i], NULL, MUTEX_NOLOCKDEP, NULL); @@ -1041,6 +1044,7 @@ dbuf_fini(void) sizeof (kmutex_t)); kmem_cache_destroy(dbuf_kmem_cache); + kmem_cache_destroy(dbuf_dirty_kmem_cache); taskq_destroy(dbu_evict_taskq); mutex_enter(&dbuf_evict_lock); @@ -2343,7 +2347,8 @@ dbuf_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx) * to make a copy of it so that the changes we make in this * transaction group won't leak out when we sync the older txg. */ - dr = kmem_zalloc(sizeof (dbuf_dirty_record_t), KM_SLEEP); + dr = kmem_cache_alloc(dbuf_dirty_kmem_cache, KM_SLEEP); + memset(dr, 0, sizeof (*dr)); list_link_init(&dr->dr_dirty_node); list_link_init(&dr->dr_dbuf_node); dr->dr_dnode = dn; @@ -2526,7 +2531,7 @@ dbuf_undirty_bonus(dbuf_dirty_record_t *dr) mutex_destroy(&dr->dt.di.dr_mtx); list_destroy(&dr->dt.di.dr_children); } - kmem_free(dr, sizeof (dbuf_dirty_record_t)); + kmem_cache_free(dbuf_dirty_kmem_cache, dr); ASSERT3U(db->db_dirtycnt, >, 0); db->db_dirtycnt -= 1; } @@ -2616,7 +2621,7 @@ dbuf_undirty(dmu_buf_impl_t *db, dmu_tx_t *tx) } } - kmem_free(dr, sizeof (dbuf_dirty_record_t)); + kmem_cache_free(dbuf_dirty_kmem_cache, dr); ASSERT(db->db_dirtycnt > 0); db->db_dirtycnt -= 1; @@ -2941,7 +2946,7 @@ dmu_buf_set_crypt_params(dmu_buf_t *db_fake, boolean_t byteorder, * (see dbuf_sync_dnode_leaf_crypt()). */ ASSERT3U(db->db.db_object, ==, DMU_META_DNODE_OBJECT); - ASSERT3U(db->db_level, ==, 0); + ASSERT0(db->db_level); ASSERT(db->db_objset->os_raw_receive); dmu_buf_will_dirty_impl(db_fake, @@ -2950,6 +2955,7 @@ dmu_buf_set_crypt_params(dmu_buf_t *db_fake, boolean_t byteorder, dr = dbuf_find_dirty_eq(db, tx->tx_txg); ASSERT3P(dr, !=, NULL); + ASSERT3U(dr->dt.dl.dr_override_state, ==, DR_NOT_OVERRIDDEN); dr->dt.dl.dr_has_raw_params = B_TRUE; dr->dt.dl.dr_byteorder = byteorder; @@ -2964,10 +2970,14 @@ dbuf_override_impl(dmu_buf_impl_t *db, const blkptr_t *bp, dmu_tx_t *tx) struct dirty_leaf *dl; dbuf_dirty_record_t *dr; + ASSERT3U(db->db.db_object, !=, DMU_META_DNODE_OBJECT); + ASSERT0(db->db_level); + dr = list_head(&db->db_dirty_records); ASSERT3P(dr, !=, NULL); ASSERT3U(dr->dr_txg, ==, tx->tx_txg); dl = &dr->dt.dl; + ASSERT0(dl->dr_has_raw_params); dl->dr_overridden_by = *bp; dl->dr_override_state = DR_OVERRIDDEN; BP_SET_LOGICAL_BIRTH(&dl->dr_overridden_by, dr->dr_txg); @@ -3040,6 +3050,7 @@ dmu_buf_write_embedded(dmu_buf_t *dbuf, void *data, ASSERT3P(dr, !=, NULL); ASSERT3U(dr->dr_txg, ==, tx->tx_txg); dl = &dr->dt.dl; + ASSERT0(dl->dr_has_raw_params); encode_embedded_bp_compressed(&dl->dr_overridden_by, data, comp, uncompressed_size, compressed_size); BPE_SET_ETYPE(&dl->dr_overridden_by, etype); @@ -5083,7 +5094,7 @@ dbuf_write_done(zio_t *zio, arc_buf_t *buf, void *vdb) dsl_pool_undirty_space(dmu_objset_pool(os), dr->dr_accounted, zio->io_txg); - kmem_free(dr, sizeof (dbuf_dirty_record_t)); + kmem_cache_free(dbuf_dirty_kmem_cache, dr); } static void diff --git a/module/zfs/dmu.c b/module/zfs/dmu.c index 3f87cfe6b..362415a25 100644 --- a/module/zfs/dmu.c +++ b/module/zfs/dmu.c @@ -1895,6 +1895,7 @@ dmu_sync_done(zio_t *zio, arc_buf_t *buf, void *varg) mutex_enter(&db->db_mtx); ASSERT(dr->dt.dl.dr_override_state == DR_IN_DMU_SYNC); if (zio->io_error == 0) { + ASSERT0(dr->dt.dl.dr_has_raw_params); dr->dt.dl.dr_nopwrite = !!(zio->io_flags & ZIO_FLAG_NOPWRITE); if (dr->dt.dl.dr_nopwrite) { blkptr_t *bp = zio->io_bp; @@ -2190,6 +2191,7 @@ dmu_sync(zio_t *pio, uint64_t txg, dmu_sync_cb_t *done, zgd_t *zgd) return (SET_ERROR(EALREADY)); } + ASSERT0(dr->dt.dl.dr_has_raw_params); ASSERT(dr->dt.dl.dr_override_state == DR_NOT_OVERRIDDEN); dr->dt.dl.dr_override_state = DR_IN_DMU_SYNC; mutex_exit(&db->db_mtx); @@ -2657,6 +2659,7 @@ dmu_brt_clone(objset_t *os, uint64_t object, uint64_t offset, uint64_t length, db = (dmu_buf_impl_t *)dbuf; bp = &bps[i]; + ASSERT3U(db->db.db_object, !=, DMU_META_DNODE_OBJECT); ASSERT0(db->db_level); ASSERT(db->db_blkid != DMU_BONUS_BLKID); ASSERT(db->db_blkid != DMU_SPILL_BLKID); @@ -2672,11 +2675,6 @@ dmu_brt_clone(objset_t *os, uint64_t object, uint64_t offset, uint64_t length, db = (dmu_buf_impl_t *)dbuf; bp = &bps[i]; - ASSERT0(db->db_level); - ASSERT(db->db_blkid != DMU_BONUS_BLKID); - ASSERT(db->db_blkid != DMU_SPILL_BLKID); - ASSERT(BP_IS_HOLE(bp) || dbuf->db_size == BP_GET_LSIZE(bp)); - dmu_buf_will_clone_or_dio(dbuf, tx); mutex_enter(&db->db_mtx); @@ -2685,6 +2683,7 @@ dmu_brt_clone(objset_t *os, uint64_t object, uint64_t offset, uint64_t length, VERIFY(dr != NULL); ASSERT3U(dr->dr_txg, ==, tx->tx_txg); dl = &dr->dt.dl; + ASSERT0(dl->dr_has_raw_params); dl->dr_overridden_by = *bp; if (!BP_IS_HOLE(bp) || BP_GET_LOGICAL_BIRTH(bp) != 0) { if (!BP_IS_EMBEDDED(bp)) { diff --git a/module/zfs/dmu_direct.c b/module/zfs/dmu_direct.c index ed96e7515..40b78b519 100644 --- a/module/zfs/dmu_direct.c +++ b/module/zfs/dmu_direct.c @@ -180,6 +180,7 @@ dmu_write_direct(zio_t *pio, dmu_buf_impl_t *db, abd_t *data, dmu_tx_t *tx) if (list_next(&db->db_dirty_records, dr_head) != NULL) zp.zp_nopwrite = B_FALSE; + ASSERT0(dr_head->dt.dl.dr_has_raw_params); ASSERT3S(dr_head->dt.dl.dr_override_state, ==, DR_NOT_OVERRIDDEN); dr_head->dt.dl.dr_override_state = DR_IN_DMU_SYNC; diff --git a/module/zfs/dnode_sync.c b/module/zfs/dnode_sync.c index f67dad002..122d7d0d1 100644 --- a/module/zfs/dnode_sync.c +++ b/module/zfs/dnode_sync.c @@ -566,7 +566,7 @@ dnode_undirty_dbufs(list_t *list) mutex_destroy(&dr->dt.di.dr_mtx); list_destroy(&dr->dt.di.dr_children); } - kmem_free(dr, sizeof (dbuf_dirty_record_t)); + kmem_cache_free(dbuf_dirty_kmem_cache, dr); dbuf_rele_and_unlock(db, (void *)(uintptr_t)txg, B_FALSE); } }