cache: lockless forward lookup with smr
This eliminates the need to take bucket locks in the common case. Concurrent lookup utilizng the same vnodes is still bottlenecked on referencing and locking path components, this will be taken care of separately. Reviewed by: kib Tested by: pho Differential Revision: https://reviews.freebsd.org/D23913
This commit is contained in:
parent
f8022be3e6
commit
5d1c042d32
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=362828
@ -56,11 +56,13 @@ __FBSDID("$FreeBSD$");
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#include <sys/proc.h>
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#include <sys/rwlock.h>
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#include <sys/sdt.h>
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#include <sys/smr.h>
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#include <sys/smp.h>
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#include <sys/syscallsubr.h>
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#include <sys/sysctl.h>
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#include <sys/sysproto.h>
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#include <sys/vnode.h>
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#include <ck_queue.h>
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#ifdef KTRACE
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#include <sys/ktrace.h>
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#endif
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@ -104,7 +106,7 @@ SDT_PROBE_DEFINE2(vfs, namecache, shrink_negative, done, "struct vnode *",
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*/
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struct namecache {
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LIST_ENTRY(namecache) nc_hash; /* hash chain */
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CK_LIST_ENTRY(namecache) nc_hash;/* hash chain */
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LIST_ENTRY(namecache) nc_src; /* source vnode list */
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TAILQ_ENTRY(namecache) nc_dst; /* destination vnode list */
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struct vnode *nc_dvp; /* vnode of parent of name */
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@ -143,6 +145,25 @@ struct namecache_ts {
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#define NCF_DVDROP 0x10
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#define NCF_NEGATIVE 0x20
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#define NCF_HOTNEGATIVE 0x40
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#define NCF_INVALID 0x80
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static bool
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cache_ncp_invalid(struct namecache *ncp)
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{
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atomic_thread_fence_acq();
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return ((ncp->nc_flag & NCF_INVALID) != 0);
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}
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static void
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cache_ncp_invalidate(struct namecache *ncp)
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{
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atomic_thread_fence_rel();
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KASSERT((ncp->nc_flag & NCF_INVALID) == 0,
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("%s: entry %p already invalid", __func__, ncp));
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ncp->nc_flag |= NCF_INVALID;
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}
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/*
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* Name caching works as follows:
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@ -192,12 +213,14 @@ struct namecache_ts {
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* the first node, locking everything in order and revalidating the state.
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*/
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VFS_SMR_DECLARE;
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/*
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* Structures associated with name caching.
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*/
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#define NCHHASH(hash) \
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(&nchashtbl[(hash) & nchash])
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static __read_mostly LIST_HEAD(nchashhead, namecache) *nchashtbl;/* Hash Table */
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static __read_mostly CK_LIST_HEAD(nchashhead, namecache) *nchashtbl;/* Hash Table */
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static u_long __read_mostly nchash; /* size of hash table */
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SYSCTL_ULONG(_debug, OID_AUTO, nchash, CTLFLAG_RD, &nchash, 0,
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"Size of namecache hash table");
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@ -275,15 +298,15 @@ cache_alloc(int len, int ts)
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if (__predict_false(ts)) {
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if (len <= CACHE_PATH_CUTOFF)
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ncp_ts = uma_zalloc(cache_zone_small_ts, M_WAITOK);
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ncp_ts = uma_zalloc_smr(cache_zone_small_ts, M_WAITOK);
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else
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ncp_ts = uma_zalloc(cache_zone_large_ts, M_WAITOK);
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ncp_ts = uma_zalloc_smr(cache_zone_large_ts, M_WAITOK);
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ncp = &ncp_ts->nc_nc;
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} else {
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if (len <= CACHE_PATH_CUTOFF)
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ncp = uma_zalloc(cache_zone_small, M_WAITOK);
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ncp = uma_zalloc_smr(cache_zone_small, M_WAITOK);
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else
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ncp = uma_zalloc(cache_zone_large, M_WAITOK);
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ncp = uma_zalloc_smr(cache_zone_large, M_WAITOK);
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}
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return (ncp);
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}
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@ -300,14 +323,14 @@ cache_free(struct namecache *ncp)
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if (__predict_false(ncp->nc_flag & NCF_TS)) {
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ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
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if (ncp->nc_nlen <= CACHE_PATH_CUTOFF)
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uma_zfree(cache_zone_small_ts, ncp_ts);
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uma_zfree_smr(cache_zone_small_ts, ncp_ts);
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else
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uma_zfree(cache_zone_large_ts, ncp_ts);
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uma_zfree_smr(cache_zone_large_ts, ncp_ts);
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} else {
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if (ncp->nc_nlen <= CACHE_PATH_CUTOFF)
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uma_zfree(cache_zone_small, ncp);
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uma_zfree_smr(cache_zone_small, ncp);
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else
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uma_zfree(cache_zone_large, ncp);
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uma_zfree_smr(cache_zone_large, ncp);
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}
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}
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@ -606,7 +629,7 @@ sysctl_debug_hashstat_rawnchash(SYSCTL_HANDLER_ARGS)
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}
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/* Scan hash tables counting entries */
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for (ncpp = nchashtbl, i = 0; i < n_nchash; ncpp++, i++)
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LIST_FOREACH(ncp, ncpp, nc_hash)
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CK_LIST_FOREACH(ncp, ncpp, nc_hash)
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cntbuf[i]++;
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cache_unlock_all_buckets();
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for (error = 0, i = 0; i < n_nchash; i++)
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@ -639,7 +662,7 @@ sysctl_debug_hashstat_nchash(SYSCTL_HANDLER_ARGS)
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/* Scan hash tables for applicable entries */
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for (ncpp = nchashtbl; n_nchash > 0; n_nchash--, ncpp++) {
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count = 0;
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LIST_FOREACH(ncp, ncpp, nc_hash) {
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CK_LIST_FOREACH(ncp, ncpp, nc_hash) {
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count++;
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}
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if (count)
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@ -860,7 +883,10 @@ cache_zap_locked(struct namecache *ncp, bool neg_locked)
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CTR2(KTR_VFS, "cache_zap(%p) vp %p", ncp,
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(ncp->nc_flag & NCF_NEGATIVE) ? NULL : ncp->nc_vp);
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LIST_REMOVE(ncp, nc_hash);
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cache_ncp_invalidate(ncp);
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CK_LIST_REMOVE(ncp, nc_hash);
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if (!(ncp->nc_flag & NCF_NEGATIVE)) {
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SDT_PROBE3(vfs, namecache, zap, done, ncp->nc_dvp,
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ncp->nc_name, ncp->nc_vp);
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@ -1013,7 +1039,7 @@ cache_zap_unlocked_bucket(struct namecache *ncp, struct componentname *cnp,
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cache_sort_vnodes(&dvlp, &vlp);
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cache_lock_vnodes(dvlp, vlp);
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rw_wlock(blp);
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LIST_FOREACH(rncp, (NCHHASH(hash)), nc_hash) {
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CK_LIST_FOREACH(rncp, (NCHHASH(hash)), nc_hash) {
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if (rncp == ncp && rncp->nc_dvp == dvp &&
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rncp->nc_nlen == cnp->cn_namelen &&
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!bcmp(rncp->nc_name, cnp->cn_nameptr, rncp->nc_nlen))
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@ -1225,12 +1251,12 @@ cache_lookup_nomakeentry(struct vnode *dvp, struct vnode **vpp,
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hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
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blp = HASH2BUCKETLOCK(hash);
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retry:
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if (LIST_EMPTY(NCHHASH(hash)))
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if (CK_LIST_EMPTY(NCHHASH(hash)))
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goto out_no_entry;
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rw_wlock(blp);
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LIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
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CK_LIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
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counter_u64_add(numchecks, 1);
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if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
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!bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))
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@ -1305,6 +1331,7 @@ cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
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uint32_t hash;
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enum vgetstate vs;
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int error, ltype;
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bool try_smr, doing_smr;
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#ifdef DEBUG_CACHE
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if (__predict_false(!doingcache)) {
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@ -1321,7 +1348,11 @@ cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
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if ((cnp->cn_flags & MAKEENTRY) == 0)
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return (cache_lookup_nomakeentry(dvp, vpp, cnp, tsp, ticksp));
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try_smr = true;
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if (cnp->cn_nameiop == CREATE)
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try_smr = false;
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retry:
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doing_smr = false;
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blp = NULL;
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dvlp = NULL;
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error = 0;
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@ -1361,10 +1392,17 @@ cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
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}
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hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
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retry_hashed:
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if (try_smr) {
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vfs_smr_enter();
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doing_smr = true;
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try_smr = false;
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} else {
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blp = HASH2BUCKETLOCK(hash);
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rw_rlock(blp);
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}
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LIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
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CK_LIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
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counter_u64_add(numchecks, 1);
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if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
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!bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))
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@ -1373,6 +1411,9 @@ cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
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/* We failed to find an entry */
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if (__predict_false(ncp == NULL)) {
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if (doing_smr)
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vfs_smr_exit();
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else
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rw_runlock(blp);
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SDT_PROBE3(vfs, namecache, lookup, miss, dvp, cnp->cn_nameptr,
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NULL);
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@ -1402,8 +1443,22 @@ cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
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ltype = VOP_ISLOCKED(dvp);
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VOP_UNLOCK(dvp);
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}
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if (doing_smr) {
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if (cache_ncp_invalid(ncp)) {
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vfs_smr_exit();
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*vpp = NULL;
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goto retry;
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}
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vs = vget_prep_smr(*vpp);
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vfs_smr_exit();
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if (vs == VGET_NONE) {
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*vpp = NULL;
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goto retry;
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}
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} else {
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vs = vget_prep(*vpp);
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cache_lookup_unlock(blp, dvlp);
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}
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error = vget_finish(*vpp, cnp->cn_lkflags, vs);
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if (cnp->cn_flags & ISDOTDOT) {
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vn_lock(dvp, ltype | LK_RETRY);
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@ -1427,21 +1482,37 @@ cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
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negative_success:
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/* We found a negative match, and want to create it, so purge */
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if (cnp->cn_nameiop == CREATE) {
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MPASS(!doing_smr);
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counter_u64_add(numnegzaps, 1);
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goto zap_and_exit;
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}
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counter_u64_add(numneghits, 1);
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if (doing_smr) {
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if ((ncp->nc_flag & NCF_HOTNEGATIVE) == 0) {
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/*
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* We need to take locks to promote the entry.
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*/
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vfs_smr_exit();
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doing_smr = false;
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goto retry_hashed;
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}
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} else {
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cache_negative_hit(ncp);
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}
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counter_u64_add(numneghits, 1);
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if (ncp->nc_flag & NCF_WHITE)
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cnp->cn_flags |= ISWHITEOUT;
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SDT_PROBE2(vfs, namecache, lookup, hit__negative, dvp,
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ncp->nc_name);
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cache_out_ts(ncp, tsp, ticksp);
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if (doing_smr)
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vfs_smr_exit();
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else
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cache_lookup_unlock(blp, dvlp);
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return (ENOENT);
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zap_and_exit:
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MPASS(!doing_smr);
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if (blp != NULL)
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error = cache_zap_rlocked_bucket(ncp, cnp, hash, blp);
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else
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@ -1775,7 +1846,7 @@ cache_enter_time(struct vnode *dvp, struct vnode *vp, struct componentname *cnp,
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* the same path name.
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*/
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ncpp = NCHHASH(hash);
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LIST_FOREACH(n2, ncpp, nc_hash) {
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CK_LIST_FOREACH(n2, ncpp, nc_hash) {
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if (n2->nc_dvp == dvp &&
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n2->nc_nlen == cnp->cn_namelen &&
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!bcmp(n2->nc_name, cnp->cn_nameptr, n2->nc_nlen)) {
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@ -1839,12 +1910,6 @@ cache_enter_time(struct vnode *dvp, struct vnode *vp, struct componentname *cnp,
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LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src);
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}
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/*
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* Insert the new namecache entry into the appropriate chain
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* within the cache entries table.
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*/
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LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
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/*
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* If the entry is "negative", we place it into the
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* "negative" cache queue, otherwise, we place it into the
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@ -1861,6 +1926,14 @@ cache_enter_time(struct vnode *dvp, struct vnode *vp, struct componentname *cnp,
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SDT_PROBE2(vfs, namecache, enter_negative, done, dvp,
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ncp->nc_name);
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}
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atomic_thread_fence_rel();
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/*
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* Insert the new namecache entry into the appropriate chain
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* within the cache entries table.
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*/
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CK_LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
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cache_enter_unlock(&cel);
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if (numneg * ncnegfactor > lnumcache)
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cache_negative_zap_one();
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@ -1908,6 +1981,11 @@ nchinit(void *dummy __unused)
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NULL, NULL, NULL, NULL, UMA_ALIGNOF(struct namecache_ts),
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UMA_ZONE_ZINIT);
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VFS_SMR_ZONE_SET(cache_zone_small);
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VFS_SMR_ZONE_SET(cache_zone_small_ts);
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VFS_SMR_ZONE_SET(cache_zone_large);
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VFS_SMR_ZONE_SET(cache_zone_large_ts);
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ncsize = desiredvnodes * ncsizefactor;
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nchashtbl = hashinit(desiredvnodes * 2, M_VFSCACHE, &nchash);
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ncbuckethash = cache_roundup_2(mp_ncpus * mp_ncpus) - 1;
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@ -1973,11 +2051,11 @@ cache_changesize(u_long newmaxvnodes)
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nchashtbl = new_nchashtbl;
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nchash = new_nchash;
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for (i = 0; i <= old_nchash; i++) {
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while ((ncp = LIST_FIRST(&old_nchashtbl[i])) != NULL) {
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while ((ncp = CK_LIST_FIRST(&old_nchashtbl[i])) != NULL) {
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hash = cache_get_hash(ncp->nc_name, ncp->nc_nlen,
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ncp->nc_dvp);
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LIST_REMOVE(ncp, nc_hash);
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LIST_INSERT_HEAD(NCHHASH(hash), ncp, nc_hash);
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CK_LIST_REMOVE(ncp, nc_hash);
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CK_LIST_INSERT_HEAD(NCHHASH(hash), ncp, nc_hash);
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}
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}
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ncsize = newncsize;
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@ -2091,7 +2169,7 @@ cache_purgevfs(struct mount *mp, bool force)
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for (j = i; j < n_nchash; j += numbucketlocks) {
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retry:
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bucket = &nchashtbl[j];
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LIST_FOREACH_SAFE(ncp, bucket, nc_hash, nnp) {
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CK_LIST_FOREACH_SAFE(ncp, bucket, nc_hash, nnp) {
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cache_assert_bucket_locked(ncp, RA_WLOCKED);
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if (ncp->nc_dvp->v_mount != mp)
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continue;
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