From: David Chinner <dgc@sgi.com>
Date: Tue, 11 Apr 2006 05:11:12 +0000 (+1000)
Subject: [XFS] Fix inode reclaim scalability regression. When a filesystem has
X-Git-Tag: v2.6.17-rc2~281
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1fc5d959d88a5f77aa7e4435f6c9d0e2d2236704;p=linux-2.6

[XFS] Fix inode reclaim scalability regression. When a filesystem has
millions of inodes cached and has sparse cluster population, removing
inodes from the cluster hash consumes excessive amounts of CPU time.
Reduce the CPU cost by making removal O(1) via use of a double linked list
for the hash chains.

SGI-PV: 951551
SGI-Modid: xfs-linux-melb:xfs-kern:25683a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>
---

diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c
index bb33113eef..b538543252 100644
--- a/fs/xfs/xfs_iget.c
+++ b/fs/xfs/xfs_iget.c
@@ -421,7 +421,10 @@ finish_inode:
 			ip->i_chash = chlnew;
 			chlnew->chl_ip = ip;
 			chlnew->chl_blkno = ip->i_blkno;
+			if (ch->ch_list)
+				ch->ch_list->chl_prev = chlnew;
 			chlnew->chl_next = ch->ch_list;
+			chlnew->chl_prev = NULL;
 			ch->ch_list = chlnew;
 			chlnew = NULL;
 		}
@@ -723,23 +726,15 @@ xfs_iextract(
 		ASSERT(ip->i_cnext == ip && ip->i_cprev == ip);
 		ASSERT(ip->i_chash != NULL);
 		chm=NULL;
-		for (chl = ch->ch_list; chl != NULL; chl = chl->chl_next) {
-			if (chl->chl_blkno == ip->i_blkno) {
-				if (chm == NULL) {
-					/* first item on the list */
-					ch->ch_list = chl->chl_next;
-				} else {
-					chm->chl_next = chl->chl_next;
-				}
-				kmem_zone_free(xfs_chashlist_zone, chl);
-				break;
-			} else {
-				ASSERT(chl->chl_ip != ip);
-				chm = chl;
-			}
-		}
-		ASSERT_ALWAYS(chl != NULL);
-       } else {
+		chl = ip->i_chash;
+		if (chl->chl_prev)
+			chl->chl_prev->chl_next = chl->chl_next;
+		else
+			ch->ch_list = chl->chl_next;
+		if (chl->chl_next)
+			chl->chl_next->chl_prev = chl->chl_prev;
+		kmem_zone_free(xfs_chashlist_zone, chl);
+	} else {
 		/* delete one inode from a non-empty list */
 		iq = ip->i_cnext;
 		iq->i_cprev = ip->i_cprev;
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 39ef9c36ea..3b544db179 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -189,6 +189,7 @@ typedef struct xfs_ihash {
  */
 typedef struct xfs_chashlist {
 	struct xfs_chashlist	*chl_next;
+	struct xfs_chashlist	*chl_prev;
 	struct xfs_inode	*chl_ip;
 	xfs_daddr_t		chl_blkno;	/* starting block number of
 						 * the cluster */