Author: mav
Date: Fri Oct 14 11:46:17 2016
New Revision: 307314
URL: https://svnweb.freebsd.org/changeset/base/307314
Log:
6988 spa_sync() spends half its time in dmu_objset_do_userquota_updates
Using a benchmark which creates 2 million files in one TXG, I observe
that the thread running spa_sync() is on CPU almost the entire time we
are syncing, and therefore can be a performance bottleneck. About 50% of
the time in spa_sync() is in dmu_objset_do_userquota_updates().
The problem is that dmu_objset_do_userquota_updates() calls
zap_increment_int(DMU_USERUSED_OBJECT) once for every file that was
modified (or created). In this benchmark, all the files are owned by the
same user/group, so all 2 million calls to zap_increment_int() are
modifying the same entry in the zap. The same issue exists for the
DMU_GROUPUSED_OBJECT.
We should keep an in-memory map from user to space delta while we are
syncing, and when we finish, iterate over the in-memory map and modify
the ZAP once per entry. This reduces the number of calls to
zap_increment_int() from "number of objects modified" to "number of
owners/groups of modified files".
This reduced the time spent in spa_sync() in the file create benchmark
by ~33%, from 11 seconds to 7 seconds.
Closes #107
Reviewed by: George Wilson <george.wil...@delphix.com>
Reviewed by: Steve Gonczi <steve.gon...@delphix.com>
Reviewed by: Ned Bass <ba...@llnl.gov>
Reviewed by: Jinshan Xiong <jinshan.xi...@intel.com>
Author: Matthew Ahrens <mahr...@delphix.com>
openzfs/openzfs@5fc46359c569369d87728ca09f8705cdff6cc8e2
Modified:
vendor-sys/illumos/dist/uts/common/fs/zfs/dmu_objset.c
Modified: vendor-sys/illumos/dist/uts/common/fs/zfs/dmu_objset.c
==============================================================================
--- vendor-sys/illumos/dist/uts/common/fs/zfs/dmu_objset.c Fri Oct 14
11:41:06 2016 (r307313)
+++ vendor-sys/illumos/dist/uts/common/fs/zfs/dmu_objset.c Fri Oct 14
11:46:17 2016 (r307314)
@@ -1207,18 +1207,83 @@ dmu_objset_userused_enabled(objset_t *os
DMU_USERUSED_DNODE(os) != NULL);
}
+typedef struct userquota_node {
+ uint64_t uqn_id;
+ int64_t uqn_delta;
+ avl_node_t uqn_node;
+} userquota_node_t;
+
+typedef struct userquota_cache {
+ avl_tree_t uqc_user_deltas;
+ avl_tree_t uqc_group_deltas;
+} userquota_cache_t;
+
+static int
+userquota_compare(const void *l, const void *r)
+{
+ const userquota_node_t *luqn = l;
+ const userquota_node_t *ruqn = r;
+
+ if (luqn->uqn_id < ruqn->uqn_id)
+ return (-1);
+ if (luqn->uqn_id > ruqn->uqn_id)
+ return (1);
+ return (0);
+}
+
static void
-do_userquota_update(objset_t *os, uint64_t used, uint64_t flags,
- uint64_t user, uint64_t group, boolean_t subtract, dmu_tx_t *tx)
+do_userquota_cacheflush(objset_t *os, userquota_cache_t *cache, dmu_tx_t *tx)
+{
+ void *cookie;
+ userquota_node_t *uqn;
+
+ ASSERT(dmu_tx_is_syncing(tx));
+
+ cookie = NULL;
+ while ((uqn = avl_destroy_nodes(&cache->uqc_user_deltas,
+ &cookie)) != NULL) {
+ VERIFY0(zap_increment_int(os, DMU_USERUSED_OBJECT,
+ uqn->uqn_id, uqn->uqn_delta, tx));
+ kmem_free(uqn, sizeof (*uqn));
+ }
+ avl_destroy(&cache->uqc_user_deltas);
+
+ cookie = NULL;
+ while ((uqn = avl_destroy_nodes(&cache->uqc_group_deltas,
+ &cookie)) != NULL) {
+ VERIFY0(zap_increment_int(os, DMU_GROUPUSED_OBJECT,
+ uqn->uqn_id, uqn->uqn_delta, tx));
+ kmem_free(uqn, sizeof (*uqn));
+ }
+ avl_destroy(&cache->uqc_group_deltas);
+}
+
+static void
+userquota_update_cache(avl_tree_t *avl, uint64_t id, int64_t delta)
+{
+ userquota_node_t search = { .uqn_id = id };
+ avl_index_t idx;
+
+ userquota_node_t *uqn = avl_find(avl, &search, &idx);
+ if (uqn == NULL) {
+ uqn = kmem_zalloc(sizeof (*uqn), KM_SLEEP);
+ uqn->uqn_id = id;
+ avl_insert(avl, uqn, idx);
+ }
+ uqn->uqn_delta += delta;
+}
+
+static void
+do_userquota_update(userquota_cache_t *cache, uint64_t used, uint64_t flags,
+ uint64_t user, uint64_t group, boolean_t subtract)
{
if ((flags & DNODE_FLAG_USERUSED_ACCOUNTED)) {
int64_t delta = DNODE_SIZE + used;
if (subtract)
delta = -delta;
- VERIFY3U(0, ==, zap_increment_int(os, DMU_USERUSED_OBJECT,
- user, delta, tx));
- VERIFY3U(0, ==, zap_increment_int(os, DMU_GROUPUSED_OBJECT,
- group, delta, tx));
+
+ userquota_update_cache(&cache->uqc_user_deltas, user, delta);
+ userquota_update_cache(&cache->uqc_group_deltas, group, delta);
}
}
@@ -1227,9 +1292,15 @@ dmu_objset_do_userquota_updates(objset_t
{
dnode_t *dn;
list_t *list = &os->os_synced_dnodes;
+ userquota_cache_t cache = { 0 };
ASSERT(list_head(list) == NULL || dmu_objset_userused_enabled(os));
+ avl_create(&cache.uqc_user_deltas, userquota_compare,
+ sizeof (userquota_node_t), offsetof(userquota_node_t, uqn_node));
+ avl_create(&cache.uqc_group_deltas, userquota_compare,
+ sizeof (userquota_node_t), offsetof(userquota_node_t, uqn_node));
+
while (dn = list_head(list)) {
int flags;
ASSERT(!DMU_OBJECT_IS_SPECIAL(dn->dn_object));
@@ -1239,32 +1310,26 @@ dmu_objset_do_userquota_updates(objset_t
/* Allocate the user/groupused objects if necessary. */
if (DMU_USERUSED_DNODE(os)->dn_type == DMU_OT_NONE) {
- VERIFY(0 == zap_create_claim(os,
+ VERIFY0(zap_create_claim(os,
DMU_USERUSED_OBJECT,
DMU_OT_USERGROUP_USED, DMU_OT_NONE, 0, tx));
- VERIFY(0 == zap_create_claim(os,
+ VERIFY0(zap_create_claim(os,
DMU_GROUPUSED_OBJECT,
DMU_OT_USERGROUP_USED, DMU_OT_NONE, 0, tx));
}
- /*
- * We intentionally modify the zap object even if the
- * net delta is zero. Otherwise
- * the block of the zap obj could be shared between
- * datasets but need to be different between them after
- * a bprewrite.
- */
-
flags = dn->dn_id_flags;
ASSERT(flags);
if (flags & DN_ID_OLD_EXIST) {
- do_userquota_update(os, dn->dn_oldused, dn->dn_oldflags,
- dn->dn_olduid, dn->dn_oldgid, B_TRUE, tx);
+ do_userquota_update(&cache,
+ dn->dn_oldused, dn->dn_oldflags,
+ dn->dn_olduid, dn->dn_oldgid, B_TRUE);
}
if (flags & DN_ID_NEW_EXIST) {
- do_userquota_update(os, DN_USED_BYTES(dn->dn_phys),
+ do_userquota_update(&cache,
+ DN_USED_BYTES(dn->dn_phys),
dn->dn_phys->dn_flags, dn->dn_newuid,
- dn->dn_newgid, B_FALSE, tx);
+ dn->dn_newgid, B_FALSE);
}
mutex_enter(&dn->dn_mtx);
@@ -1285,6 +1350,7 @@ dmu_objset_do_userquota_updates(objset_t
list_remove(list, dn);
dnode_rele(dn, list);
}
+ do_userquota_cacheflush(os, &cache, tx);
}
/*
_______________________________________________
svn-src-all@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/svn-src-all
To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
