Author: mjg
Date: Fri Sep 27 19:12:43 2019
New Revision: 352811
URL: https://svnweb.freebsd.org/changeset/base/352811
Log:
cache: make negative list shrinking a little bit concurrent
Continue protecting demotion from the hotlist and selection of the
target list with the ncneg_shrink_lock lock, but drop it before
relocking to zap the node.
While here count how many times we skipped shrinking due to the lock
being already taken.
Sponsored by: The FreeBSD Foundation
Modified:
head/sys/kern/vfs_cache.c
Modified: head/sys/kern/vfs_cache.c
==============================================================================
--- head/sys/kern/vfs_cache.c Fri Sep 27 19:12:20 2019 (r352810)
+++ head/sys/kern/vfs_cache.c Fri Sep 27 19:12:43 2019 (r352811)
@@ -380,8 +380,6 @@ STATNODE_COUNTER(numfullpathfail2,
"Number of fullpath search errors (VOP_VPTOCNP failures)");
STATNODE_COUNTER(numfullpathfail4, "Number of fullpath search errors
(ENOMEM)");
STATNODE_COUNTER(numfullpathfound, "Number of successful fullpath calls");
-static long numneg_evicted; STATNODE_ULONG(numneg_evicted,
- "Number of negative entries evicted when adding a new entry");
STATNODE_COUNTER(zap_and_exit_bucket_relock_success,
"Number of successful removals after relocking");
static long zap_and_exit_bucket_fail; STATNODE_ULONG(zap_and_exit_bucket_fail,
@@ -392,6 +390,10 @@ static long cache_lock_vnodes_cel_3_failures;
STATNODE_ULONG(cache_lock_vnodes_cel_3_failures,
"Number of times 3-way vnode locking failed");
STATNODE_ULONG(numhotneg, "Number of hot negative entries");
+STATNODE_COUNTER(numneg_evicted,
+ "Number of negative entries evicted when adding a new entry");
+STATNODE_COUNTER(shrinking_skipped,
+ "Number of times shrinking was already in progress");
static void cache_zap_locked(struct namecache *ncp, bool neg_locked);
static int vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode
*rdir,
@@ -809,8 +811,10 @@ cache_negative_zap_one(void)
struct rwlock *blp;
if (mtx_owner(&ncneg_shrink_lock) != NULL ||
- !mtx_trylock(&ncneg_shrink_lock))
+ !mtx_trylock(&ncneg_shrink_lock)) {
+ counter_u64_add(shrinking_skipped, 1);
return;
+ }
mtx_lock(&ncneg_hot.nl_lock);
ncp = TAILQ_FIRST(&ncneg_hot.nl_list);
@@ -831,8 +835,9 @@ cache_negative_zap_one(void)
shrink_list_turn = 0;
if (ncp == NULL && shrink_list_turn == 0)
cache_negative_shrink_select(shrink_list_turn, &ncp, &neglist);
+ mtx_unlock(&ncneg_shrink_lock);
if (ncp == NULL)
- goto out;
+ return;
MPASS(ncp->nc_flag & NCF_NEGATIVE);
dvlp = VP2VNODELOCK(ncp->nc_dvp);
@@ -845,19 +850,15 @@ cache_negative_zap_one(void)
if (ncp != ncp2 || dvlp != VP2VNODELOCK(ncp2->nc_dvp) ||
blp != NCP2BUCKETLOCK(ncp2) || !(ncp2->nc_flag & NCF_NEGATIVE)) {
ncp = NULL;
- goto out_unlock_all;
+ } else {
+ SDT_PROBE3(vfs, namecache, shrink_negative, done, ncp->nc_dvp,
+ ncp->nc_name, ncp->nc_neghits);
+ cache_zap_locked(ncp, true);
+ counter_u64_add(numneg_evicted, 1);
}
- SDT_PROBE3(vfs, namecache, shrink_negative, done, ncp->nc_dvp,
- ncp->nc_name, ncp->nc_neghits);
-
- cache_zap_locked(ncp, true);
- numneg_evicted++;
-out_unlock_all:
mtx_unlock(&neglist->nl_lock);
rw_wunlock(blp);
mtx_unlock(dvlp);
-out:
- mtx_unlock(&ncneg_shrink_lock);
cache_free(ncp);
}
@@ -2016,6 +2017,8 @@ nchinit(void *dummy __unused)
numfullpathfail4 = counter_u64_alloc(M_WAITOK);
numfullpathfound = counter_u64_alloc(M_WAITOK);
zap_and_exit_bucket_relock_success = counter_u64_alloc(M_WAITOK);
+ numneg_evicted = counter_u64_alloc(M_WAITOK);
+ shrinking_skipped = counter_u64_alloc(M_WAITOK);
}
SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nchinit, NULL);
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