Author: mjg
Date: Wed Sep 23 10:44:49 2020
New Revision: 366070
URL: https://svnweb.freebsd.org/changeset/base/366070
Log:
cache: reimplement purgevfs to iterate vnodes instead of the entire hash
The entire cache scan was a leftover from the old implementation.
It is incredibly wasteful in presence of several mount points and does not
win much even for single ones.
Modified:
head/sys/kern/vfs_cache.c
Modified: head/sys/kern/vfs_cache.c
==============================================================================
--- head/sys/kern/vfs_cache.c Wed Sep 23 10:42:41 2020 (r366069)
+++ head/sys/kern/vfs_cache.c Wed Sep 23 10:44:49 2020 (r366070)
@@ -491,20 +491,6 @@ static int vn_fullpath_dir(struct vnode *vp, struct vn
static MALLOC_DEFINE(M_VFSCACHE, "vfscache", "VFS name cache entries");
-static int cache_yield;
-SYSCTL_INT(_vfs_cache, OID_AUTO, yield, CTLFLAG_RD, &cache_yield, 0,
- "Number of times cache called yield");
-
-static void __noinline
-cache_maybe_yield(void)
-{
-
- if (should_yield()) {
- cache_yield++;
- kern_yield(PRI_USER);
- }
-}
-
static inline void
cache_assert_vlp_locked(struct mtx *vlp)
{
@@ -1212,51 +1198,6 @@ cache_zap_locked_bucket(struct namecache *ncp, struct
return (cache_zap_unlocked_bucket(ncp, cnp, dvp, dvlp, vlp, hash, blp));
}
-static int
-cache_zap_locked_bucket_kl(struct namecache *ncp, struct mtx *blp,
- struct mtx **vlpp1, struct mtx **vlpp2)
-{
- struct mtx *dvlp, *vlp;
-
- cache_assert_bucket_locked(ncp);
-
- dvlp = VP2VNODELOCK(ncp->nc_dvp);
- vlp = NULL;
- if (!(ncp->nc_flag & NCF_NEGATIVE))
- vlp = VP2VNODELOCK(ncp->nc_vp);
- cache_sort_vnodes(&dvlp, &vlp);
-
- if (*vlpp1 == dvlp && *vlpp2 == vlp) {
- cache_zap_locked(ncp);
- cache_unlock_vnodes(dvlp, vlp);
- *vlpp1 = NULL;
- *vlpp2 = NULL;
- return (0);
- }
-
- if (*vlpp1 != NULL)
- mtx_unlock(*vlpp1);
- if (*vlpp2 != NULL)
- mtx_unlock(*vlpp2);
- *vlpp1 = NULL;
- *vlpp2 = NULL;
-
- if (cache_trylock_vnodes(dvlp, vlp) == 0) {
- cache_zap_locked(ncp);
- cache_unlock_vnodes(dvlp, vlp);
- return (0);
- }
-
- mtx_unlock(blp);
- *vlpp1 = dvlp;
- *vlpp2 = vlp;
- if (*vlpp1 != NULL)
- mtx_lock(*vlpp1);
- mtx_lock(*vlpp2);
- mtx_lock(blp);
- return (EAGAIN);
-}
-
static __noinline int
cache_remove_cnp(struct vnode *dvp, struct componentname *cnp)
{
@@ -2316,14 +2257,26 @@ retry:
}
}
+/*
+ * Opportunistic check to see if there is anything to do.
+ */
+static bool
+cache_has_entries(struct vnode *vp)
+{
+
+ if (LIST_EMPTY(&vp->v_cache_src) && TAILQ_EMPTY(&vp->v_cache_dst) &&
+ vp->v_cache_dd == NULL)
+ return (false);
+ return (true);
+}
+
void
cache_purge(struct vnode *vp)
{
struct mtx *vlp;
SDT_PROBE1(vfs, namecache, purge, done, vp);
- if (LIST_EMPTY(&vp->v_cache_src) && TAILQ_EMPTY(&vp->v_cache_dst) &&
- vp->v_cache_dd == NULL)
+ if (!cache_has_entries(vp))
return;
vlp = VP2VNODELOCK(vp);
mtx_lock(vlp);
@@ -2418,49 +2371,25 @@ cache_rename(struct vnode *fdvp, struct vnode *fvp, st
void
cache_purgevfs(struct mount *mp, bool force)
{
- TAILQ_HEAD(, namecache) ncps;
- struct mtx *vlp1, *vlp2;
- struct mtx *blp;
- struct nchashhead *bucket;
- struct namecache *ncp, *nnp;
- u_long i, j, n_nchash;
- int error;
+ struct vnode *vp, *mvp;
- /* Scan hash tables for applicable entries */
SDT_PROBE1(vfs, namecache, purgevfs, done, mp);
if (!force && mp->mnt_nvnodelistsize <= ncpurgeminvnodes)
return;
- TAILQ_INIT(&ncps);
- n_nchash = nchash + 1;
- vlp1 = vlp2 = NULL;
- for (i = 0; i < numbucketlocks; i++) {
- blp = (struct mtx *)&bucketlocks[i];
- mtx_lock(blp);
- for (j = i; j < n_nchash; j += numbucketlocks) {
-retry:
- bucket = &nchashtbl[j];
- CK_SLIST_FOREACH_SAFE(ncp, bucket, nc_hash, nnp) {
- cache_assert_bucket_locked(ncp);
- if (ncp->nc_dvp->v_mount != mp)
- continue;
- error = cache_zap_locked_bucket_kl(ncp, blp,
- &vlp1, &vlp2);
- if (error != 0)
- goto retry;
- TAILQ_INSERT_HEAD(&ncps, ncp, nc_dst);
- }
- }
- mtx_unlock(blp);
- if (vlp1 == NULL && vlp2 == NULL)
- cache_maybe_yield();
- }
- if (vlp1 != NULL)
- mtx_unlock(vlp1);
- if (vlp2 != NULL)
- mtx_unlock(vlp2);
- TAILQ_FOREACH_SAFE(ncp, &ncps, nc_dst, nnp) {
- cache_free(ncp);
+ /*
+ * Somewhat wasteful iteration over all vnodes. Would be better to
+ * support filtering and avoid the interlock to begin with.
+ */
+ MNT_VNODE_FOREACH_ALL(vp, mp, mvp) {
+ if (!cache_has_entries(vp)) {
+ VI_UNLOCK(vp);
+ continue;
+ }
+ vholdl(vp);
+ VI_UNLOCK(vp);
+ cache_purge(vp);
+ vdrop(vp);
}
}
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