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Date:      Sun, 19 Jan 2020 05:37:27 +0000 (UTC)
From:      Mateusz Guzik <mjg@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r356880 - head/sys/kern
Message-ID:  <202001190537.00J5bRw7090354@repo.freebsd.org>
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Author: mjg
Date: Sun Jan 19 05:37:27 2020
New Revision: 356880
URL: https://svnweb.freebsd.org/changeset/base/356880

Log:
  cache: convert numcachehv to counter(9) on 64-bit platforms

Modified:
  head/sys/kern/vfs_cache.c

Modified: head/sys/kern/vfs_cache.c
==============================================================================
--- head/sys/kern/vfs_cache.c	Sun Jan 19 05:36:45 2020	(r356879)
+++ head/sys/kern/vfs_cache.c	Sun Jan 19 05:37:27 2020	(r356880)
@@ -205,7 +205,6 @@ SYSCTL_ULONG(_vfs, OID_AUTO, ncnegfactor, CTLFLAG_RW, 
     "Ratio of negative namecache entries");
 static u_long __exclusive_cache_line	numneg;	/* number of negative entries allocated */
 static u_long __exclusive_cache_line	numcache;/* number of cache entries allocated */
-static u_long __exclusive_cache_line	numcachehv;/* number of cache entries with vnodes held */
 u_int ncsizefactor = 2;
 SYSCTL_UINT(_vfs, OID_AUTO, ncsizefactor, CTLFLAG_RW, &ncsizefactor, 0,
     "Size factor for namecache");
@@ -341,6 +340,16 @@ SYSCTL_INT(_debug_sizeof, OID_AUTO, namecache, CTLFLAG
     sizeof(struct namecache), "sizeof(struct namecache)");
 
 /*
+ * Use counter(9) for numcachehv if the machine is 64-bit.
+ *
+ * Stick to an atomic for the rest since there is no long-sized equivalent and
+ * 64-bit size is both way more than needed and a pessimization.
+ */
+#ifdef __LP64__
+#define CACHE_NUMCACHEHV_U64
+#endif
+
+/*
  * The new name cache statistics
  */
 static SYSCTL_NODE(_vfs, OID_AUTO, cache, CTLFLAG_RW, 0,
@@ -352,7 +361,12 @@ static SYSCTL_NODE(_vfs, OID_AUTO, cache, CTLFLAG_RW, 
 	SYSCTL_COUNTER_U64(_vfs_cache, OID_AUTO, name, CTLFLAG_RD, &name, descr);
 STATNODE_ULONG(numneg, "Number of negative cache entries");
 STATNODE_ULONG(numcache, "Number of cache entries");
+#ifdef CACHE_NUMCACHEHV_U64
+STATNODE_COUNTER(numcachehv, "Number of namecache entries with vnodes held");
+#else
+static u_long __exclusive_cache_line	numcachehv;/* number of cache entries with vnodes held */
 STATNODE_ULONG(numcachehv, "Number of namecache entries with vnodes held");
+#endif
 STATNODE_COUNTER(numcalls, "Number of cache lookups");
 STATNODE_COUNTER(dothits, "Number of '.' hits");
 STATNODE_COUNTER(dotdothits, "Number of '..' hits");
@@ -393,6 +407,36 @@ static int vn_fullpath1(struct thread *td, struct vnod
 
 static MALLOC_DEFINE(M_VFSCACHE, "vfscache", "VFS name cache entries");
 
+#ifdef CACHE_NUMCACHEHV_U64
+static void
+cache_numcachehv_inc(void)
+{
+
+	counter_u64_add_protected(numcachehv, 1);
+}
+
+static void
+cache_numcachehv_dec(void)
+{
+
+	counter_u64_add_protected(numcachehv, -1);
+}
+#else
+static void
+cache_numcachehv_inc(void)
+{
+
+	atomic_add_long(&numcachehv, 1);
+}
+
+static void
+cache_numcachehv_dec(void)
+{
+
+	atomic_subtract_long(&numcachehv, 1);
+}
+#endif
+
 static int cache_yield;
 SYSCTL_INT(_vfs_cache, OID_AUTO, yield, CTLFLAG_RD, &cache_yield, 0,
     "Number of times cache called yield");
@@ -873,7 +917,7 @@ cache_zap_locked(struct namecache *ncp, bool neg_locke
 		LIST_REMOVE(ncp, nc_src);
 		if (LIST_EMPTY(&ncp->nc_dvp->v_cache_src)) {
 			ncp->nc_flag |= NCF_DVDROP;
-			atomic_subtract_rel_long(&numcachehv, 1);
+			cache_numcachehv_dec();
 		}
 	}
 	atomic_subtract_rel_long(&numcache, 1);
@@ -1742,7 +1786,7 @@ cache_enter_time(struct vnode *dvp, struct vnode *vp, 
 	held_dvp = false;
 	if (LIST_EMPTY(&dvp->v_cache_src) && flag != NCF_ISDOTDOT) {
 		vhold(dvp);
-		atomic_add_long(&numcachehv, 1);
+		cache_numcachehv_inc();
 		held_dvp = true;
 	}
 
@@ -1837,7 +1881,7 @@ cache_enter_time(struct vnode *dvp, struct vnode *vp, 
 		if (LIST_EMPTY(&dvp->v_cache_src)) {
 			if (!held_dvp) {
 				vhold(dvp);
-				atomic_add_long(&numcachehv, 1);
+				cache_numcachehv_inc();
 			}
 		} else {
 			if (held_dvp) {
@@ -1848,7 +1892,7 @@ cache_enter_time(struct vnode *dvp, struct vnode *vp, 
 				 * this from changing.
 				 */
 				vdrop(dvp);
-				atomic_subtract_long(&numcachehv, 1);
+				cache_numcachehv_dec();
 			}
 		}
 		LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src);
@@ -1886,7 +1930,7 @@ out_unlock_free:
 	cache_free(ncp);
 	if (held_dvp) {
 		vdrop(dvp);
-		atomic_subtract_long(&numcachehv, 1);
+		cache_numcachehv_dec();
 	}
 	return;
 }
@@ -1957,6 +2001,9 @@ nchinit(void *dummy __unused)
 
 	mtx_init(&ncneg_shrink_lock, "ncnegs", NULL, MTX_DEF);
 
+#ifdef CACHE_NUMCACHEHV_U64
+	numcachehv = counter_u64_alloc(M_WAITOK);
+#endif
 	numcalls = counter_u64_alloc(M_WAITOK);
 	dothits = counter_u64_alloc(M_WAITOK);
 	dotdothits = counter_u64_alloc(M_WAITOK);

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