From 534688948c395619af328c60ba3b863bfcf2ef20 Mon Sep 17 00:00:00 2001 From: Alexander Motin Date: Tue, 19 Nov 2024 10:00:16 -0500 Subject: [PATCH] Remove hash_elements_max accounting from DBUF and ARC Those values require global atomics to get current hash_elements values in few of the hottest code paths, while in all the years I never cared about it. If somebody wants, it should be easy to get it by periodic sampling, since neither ARC header nor DBUF counts change so fast that it would be difficult to catch. For now I've left hash_elements_max kstat for ARC, since it was used/reported by arc_summary and it would break older versions, but now it just reports the current value. Reviewed-by: Brian Behlendorf Signed-off-by: Alexander Motin Sponsored by: iXsystems, Inc. Closes #16759 --- cmd/arc_summary | 5 +---- include/sys/arc_impl.h | 1 + module/zfs/arc.c | 13 +++++++------ module/zfs/dbuf.c | 12 +++++++----- 4 files changed, 16 insertions(+), 15 deletions(-) diff --git a/cmd/arc_summary b/cmd/arc_summary index c24d400fa39a..72381d266e64 100755 --- a/cmd/arc_summary +++ b/cmd/arc_summary @@ -662,10 +662,7 @@ def section_arc(kstats_dict): print() print('ARC hash breakdown:') - prt_i1('Elements max:', f_hits(arc_stats['hash_elements_max'])) - prt_i2('Elements current:', - f_perc(arc_stats['hash_elements'], arc_stats['hash_elements_max']), - f_hits(arc_stats['hash_elements'])) + prt_i1('Elements:', f_hits(arc_stats['hash_elements'])) prt_i1('Collisions:', f_hits(arc_stats['hash_collisions'])) prt_i1('Chain max:', f_hits(arc_stats['hash_chain_max'])) diff --git a/include/sys/arc_impl.h b/include/sys/arc_impl.h index 01693d72dda8..b2839bdf1485 100644 --- a/include/sys/arc_impl.h +++ b/include/sys/arc_impl.h @@ -942,6 +942,7 @@ typedef struct arc_sums { wmsum_t arcstat_evict_l2_eligible_mru; wmsum_t arcstat_evict_l2_ineligible; wmsum_t arcstat_evict_l2_skip; + wmsum_t arcstat_hash_elements; wmsum_t arcstat_hash_collisions; wmsum_t arcstat_hash_chains; aggsum_t arcstat_size; diff --git a/module/zfs/arc.c b/module/zfs/arc.c index 2ece7d67704f..0c086fc21225 100644 --- a/module/zfs/arc.c +++ b/module/zfs/arc.c @@ -1074,12 +1074,9 @@ buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) ARCSTAT_BUMP(arcstat_hash_collisions); if (i == 1) ARCSTAT_BUMP(arcstat_hash_chains); - ARCSTAT_MAX(arcstat_hash_chain_max, i); } - uint64_t he = atomic_inc_64_nv( - &arc_stats.arcstat_hash_elements.value.ui64); - ARCSTAT_MAX(arcstat_hash_elements_max, he); + ARCSTAT_BUMP(arcstat_hash_elements); return (NULL); } @@ -1103,8 +1100,7 @@ buf_hash_remove(arc_buf_hdr_t *hdr) arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE); /* collect some hash table performance data */ - atomic_dec_64(&arc_stats.arcstat_hash_elements.value.ui64); - + ARCSTAT_BUMPDOWN(arcstat_hash_elements); if (buf_hash_table.ht_table[idx] && buf_hash_table.ht_table[idx]->b_hash_next == NULL) ARCSTAT_BUMPDOWN(arcstat_hash_chains); @@ -7008,6 +7004,9 @@ arc_kstat_update(kstat_t *ksp, int rw) wmsum_value(&arc_sums.arcstat_evict_l2_ineligible); as->arcstat_evict_l2_skip.value.ui64 = wmsum_value(&arc_sums.arcstat_evict_l2_skip); + as->arcstat_hash_elements.value.ui64 = + as->arcstat_hash_elements_max.value.ui64 = + wmsum_value(&arc_sums.arcstat_hash_elements); as->arcstat_hash_collisions.value.ui64 = wmsum_value(&arc_sums.arcstat_hash_collisions); as->arcstat_hash_chains.value.ui64 = @@ -7432,6 +7431,7 @@ arc_state_init(void) wmsum_init(&arc_sums.arcstat_evict_l2_eligible_mru, 0); wmsum_init(&arc_sums.arcstat_evict_l2_ineligible, 0); wmsum_init(&arc_sums.arcstat_evict_l2_skip, 0); + wmsum_init(&arc_sums.arcstat_hash_elements, 0); wmsum_init(&arc_sums.arcstat_hash_collisions, 0); wmsum_init(&arc_sums.arcstat_hash_chains, 0); aggsum_init(&arc_sums.arcstat_size, 0); @@ -7590,6 +7590,7 @@ arc_state_fini(void) wmsum_fini(&arc_sums.arcstat_evict_l2_eligible_mru); wmsum_fini(&arc_sums.arcstat_evict_l2_ineligible); wmsum_fini(&arc_sums.arcstat_evict_l2_skip); + wmsum_fini(&arc_sums.arcstat_hash_elements); wmsum_fini(&arc_sums.arcstat_hash_collisions); wmsum_fini(&arc_sums.arcstat_hash_chains); aggsum_fini(&arc_sums.arcstat_size); diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c index 7b8fdaae0f8e..cbd07d19a7f9 100644 --- a/module/zfs/dbuf.c +++ b/module/zfs/dbuf.c @@ -89,7 +89,6 @@ typedef struct dbuf_stats { kstat_named_t hash_misses; kstat_named_t hash_collisions; kstat_named_t hash_elements; - kstat_named_t hash_elements_max; /* * Number of sublists containing more than one dbuf in the dbuf * hash table. Keep track of the longest hash chain. @@ -134,7 +133,6 @@ dbuf_stats_t dbuf_stats = { { "hash_misses", KSTAT_DATA_UINT64 }, { "hash_collisions", KSTAT_DATA_UINT64 }, { "hash_elements", KSTAT_DATA_UINT64 }, - { "hash_elements_max", KSTAT_DATA_UINT64 }, { "hash_chains", KSTAT_DATA_UINT64 }, { "hash_chain_max", KSTAT_DATA_UINT64 }, { "hash_insert_race", KSTAT_DATA_UINT64 }, @@ -154,6 +152,7 @@ struct { wmsum_t hash_hits; wmsum_t hash_misses; wmsum_t hash_collisions; + wmsum_t hash_elements; wmsum_t hash_chains; wmsum_t hash_insert_race; wmsum_t metadata_cache_count; @@ -432,8 +431,7 @@ dbuf_hash_insert(dmu_buf_impl_t *db) db->db_hash_next = h->hash_table[idx]; h->hash_table[idx] = db; mutex_exit(DBUF_HASH_MUTEX(h, idx)); - uint64_t he = atomic_inc_64_nv(&dbuf_stats.hash_elements.value.ui64); - DBUF_STAT_MAX(hash_elements_max, he); + DBUF_STAT_BUMP(hash_elements); return (NULL); } @@ -506,7 +504,7 @@ dbuf_hash_remove(dmu_buf_impl_t *db) h->hash_table[idx]->db_hash_next == NULL) DBUF_STAT_BUMPDOWN(hash_chains); mutex_exit(DBUF_HASH_MUTEX(h, idx)); - atomic_dec_64(&dbuf_stats.hash_elements.value.ui64); + DBUF_STAT_BUMPDOWN(hash_elements); } typedef enum { @@ -903,6 +901,8 @@ dbuf_kstat_update(kstat_t *ksp, int rw) wmsum_value(&dbuf_sums.hash_misses); ds->hash_collisions.value.ui64 = wmsum_value(&dbuf_sums.hash_collisions); + ds->hash_elements.value.ui64 = + wmsum_value(&dbuf_sums.hash_elements); ds->hash_chains.value.ui64 = wmsum_value(&dbuf_sums.hash_chains); ds->hash_insert_race.value.ui64 = @@ -1004,6 +1004,7 @@ dbuf_init(void) wmsum_init(&dbuf_sums.hash_hits, 0); wmsum_init(&dbuf_sums.hash_misses, 0); wmsum_init(&dbuf_sums.hash_collisions, 0); + wmsum_init(&dbuf_sums.hash_elements, 0); wmsum_init(&dbuf_sums.hash_chains, 0); wmsum_init(&dbuf_sums.hash_insert_race, 0); wmsum_init(&dbuf_sums.metadata_cache_count, 0); @@ -1077,6 +1078,7 @@ dbuf_fini(void) wmsum_fini(&dbuf_sums.hash_hits); wmsum_fini(&dbuf_sums.hash_misses); wmsum_fini(&dbuf_sums.hash_collisions); + wmsum_fini(&dbuf_sums.hash_elements); wmsum_fini(&dbuf_sums.hash_chains); wmsum_fini(&dbuf_sums.hash_insert_race); wmsum_fini(&dbuf_sums.metadata_cache_count);