[XFS] Move the XFS inode to the front of its hash list on a cache hit

SGI Modid: xfs-linux:xfs-kern:21915a Signed-off-by: Nathan Scott <nathans@sgi.com> Signed-off-by: Christoph Hellwig <hch@sgi.com>

[XFS] Move the XFS inode to the front of its hash list on a cache hit
SGI Modid: xfs-linux:xfs-kern:21915a Signed-off-by: Nathan Scott <nathans@sgi.com> Signed-off-by: Christoph Hellwig <hch@sgi.com>
Nathan Scott · Christoph Hellwig
1 parent bfd4bda097
Showing 1 changed file with 50 additions and 1 deletions Side-by-side Diff
fs/xfs/xfs_iget.c
@@ -136,6 +136,40 @@
 }
  
 /*
+ * Try to move an inode to the front of its hash list if possible
+ * (and if its not there already).  Called right after obtaining
+ * the list version number and then dropping the read_lock on the
+ * hash list in question (which is done right after looking up the
+ * inode in question...).
+ */
+STATIC void
+xfs_ihash_promote(
+	xfs_ihash_t	*ih,
+	xfs_inode_t	*ip,
+	ulong		version)
+{
+	xfs_inode_t	*iq;
+
+	if ((ip->i_prevp != &ih->ih_next) && write_trylock(&ih->ih_lock)) {
+		if (likely(version == ih->ih_version)) {
+			/* remove from list */
+			if ((iq = ip->i_next)) {
+				iq->i_prevp = ip->i_prevp;
+			}
+			*ip->i_prevp = iq;
+
+			/* insert at list head */
+			iq = ih->ih_next;
+			iq->i_prevp = &ip->i_next;
+			ip->i_next = iq;
+			ip->i_prevp = &ih->ih_next;
+			ih->ih_next = ip;
+		}
+		write_unlock(&ih->ih_lock);
+	}
+}
+
+/*
  * Look up an inode by number in the given file system.
  * The inode is looked up in the hash table for the file system
  * represented by the mount point parameter mp.  Each bucket of
  
@@ -229,7 +263,9 @@
 				XFS_STATS_INC(xs_ig_found);
  
 				ip->i_flags &= ~XFS_IRECLAIMABLE;
+				version = ih->ih_version;
 				read_unlock(&ih->ih_lock);
+				xfs_ihash_promote(ih, ip, version);
  
 				XFS_MOUNT_ILOCK(mp);
 				list_del_init(&ip->i_reclaim);
  
@@ -259,8 +295,15 @@
 						inode_vp, vp);
 			}
  
+			/*
+			 * Inode cache hit: if ip is not at the front of
+			 * its hash chain, move it there now.
+			 * Do this with the lock held for update, but
+			 * do statistics after releasing the lock.
+			 */
+			version = ih->ih_version;
 			read_unlock(&ih->ih_lock);
-
+			xfs_ihash_promote(ih, ip, version);
 			XFS_STATS_INC(xs_ig_found);
  
 finish_inode:
@@ -547,6 +590,7 @@
 {
 	xfs_ihash_t	*ih;
 	xfs_inode_t	*ip;
+	ulong		version;
  
 	ih = XFS_IHASH(mp, ino);
 	read_lock(&ih->ih_lock);
  
  
@@ -554,11 +598,15 @@
 		if (ip->i_ino == ino) {
 			/*
 			 * If we find it and tp matches, return it.
+			 * Also move it to the front of the hash list
+			 * if we find it and it is not already there.
 			 * Otherwise break from the loop and return
 			 * NULL.
 			 */
 			if (ip->i_transp == tp) {
+				version = ih->ih_version;
 				read_unlock(&ih->ih_lock);
+				xfs_ihash_promote(ih, ip, version);
 				return (ip);
 			}
 			break;
@@ -685,6 +733,7 @@
 		iq->i_prevp = ip->i_prevp;
 	}
 	*ip->i_prevp = iq;
+	ih->ih_version++;
 	write_unlock(&ih->ih_lock);
  
 	/*
...	...	@@ -136,6 +136,40 @@
136	136	}
137	137
138	138	/*
	139	+ * Try to move an inode to the front of its hash list if possible
	140	+ * (and if its not there already). Called right after obtaining
	141	+ * the list version number and then dropping the read_lock on the
	142	+ * hash list in question (which is done right after looking up the
	143	+ * inode in question...).
	144	+ */
	145	+STATIC void
	146	+xfs_ihash_promote(
	147	+ xfs_ihash_t *ih,
	148	+ xfs_inode_t *ip,
	149	+ ulong version)
	150	+{
	151	+ xfs_inode_t *iq;
	152	+
	153	+ if ((ip->i_prevp != &ih->ih_next) && write_trylock(&ih->ih_lock)) {
	154	+ if (likely(version == ih->ih_version)) {
	155	+ /* remove from list */
	156	+ if ((iq = ip->i_next)) {
	157	+ iq->i_prevp = ip->i_prevp;
	158	+ }
	159	+ *ip->i_prevp = iq;
	160	+
	161	+ /* insert at list head */
	162	+ iq = ih->ih_next;
	163	+ iq->i_prevp = &ip->i_next;
	164	+ ip->i_next = iq;
	165	+ ip->i_prevp = &ih->ih_next;
	166	+ ih->ih_next = ip;
	167	+ }
	168	+ write_unlock(&ih->ih_lock);
	169	+ }
	170	+}
	171	+
	172	+/*
139	173	* Look up an inode by number in the given file system.
140	174	* The inode is looked up in the hash table for the file system
141	175	* represented by the mount point parameter mp. Each bucket of
142	176
...	...	@@ -229,7 +263,9 @@
229	263	XFS_STATS_INC(xs_ig_found);
230	264
231	265	ip->i_flags &= ~XFS_IRECLAIMABLE;
	266	+ version = ih->ih_version;
232	267	read_unlock(&ih->ih_lock);
	268	+ xfs_ihash_promote(ih, ip, version);
233	269
234	270	XFS_MOUNT_ILOCK(mp);
235	271	list_del_init(&ip->i_reclaim);
236	272
...	...	@@ -259,8 +295,15 @@
259	295	inode_vp, vp);
260	296	}
261	297
	298	+ /*
	299	+ * Inode cache hit: if ip is not at the front of
	300	+ * its hash chain, move it there now.
	301	+ * Do this with the lock held for update, but
	302	+ * do statistics after releasing the lock.
	303	+ */
	304	+ version = ih->ih_version;
262	305	read_unlock(&ih->ih_lock);
263		-
	306	+ xfs_ihash_promote(ih, ip, version);
264	307	XFS_STATS_INC(xs_ig_found);
265	308
266	309	finish_inode:
...	...	@@ -547,6 +590,7 @@
547	590	{
548	591	xfs_ihash_t *ih;
549	592	xfs_inode_t *ip;
	593	+ ulong version;
550	594
551	595	ih = XFS_IHASH(mp, ino);
552	596	read_lock(&ih->ih_lock);
553	597
554	598
...	...	@@ -554,11 +598,15 @@
554	598	if (ip->i_ino == ino) {
555	599	/*
556	600	* If we find it and tp matches, return it.
	601	+ * Also move it to the front of the hash list
	602	+ * if we find it and it is not already there.
557	603	* Otherwise break from the loop and return
558	604	* NULL.
559	605	*/
560	606	if (ip->i_transp == tp) {
	607	+ version = ih->ih_version;
561	608	read_unlock(&ih->ih_lock);
	609	+ xfs_ihash_promote(ih, ip, version);
562	610	return (ip);
563	611	}
564	612	break;
...	...	@@ -685,6 +733,7 @@
685	733	iq->i_prevp = ip->i_prevp;
686	734	}
687	735	*ip->i_prevp = iq;
	736	+ ih->ih_version++;
688	737	write_unlock(&ih->ih_lock);
689	738
690	739	/*