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cache: make negative list shrinking a little bit concurrent

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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
This commit is contained in:
Mateusz Guzik 2019-09-27 19:12:43 +00:00
parent 95c6dd890a
commit 312196df0f
1 changed files with 16 additions and 13 deletions
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29
sys/kern/vfs_cache.c
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@ -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);