From: Ajeet Yadav <ajeet.yadav.77@gmail.com>
Date: Tue, 27 Dec 2011 09:40:04 +0000 (+0530)
Subject: Squashfs: optimise squashfs_cache_get entry search
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=d7fbd893388d9e86d29b7cfbd5457bcf03496fbf;p=linux-beck.git

Squashfs: optimise squashfs_cache_get entry search

squashfs_cache_get() iterates over all entries to search for
 block its looking for. Often get() / put() are called for
 same block.

If we cache the current entry index, then we can optimise the
subsequent *_get() calls.

Signed-off-by: Ajeet Yadav <ajeet.yadav.77@gmail.com>
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
---

diff --git a/fs/squashfs/cache.c b/fs/squashfs/cache.c
index ea6e798e548b..af0b73802592 100644
--- a/fs/squashfs/cache.c
+++ b/fs/squashfs/cache.c
@@ -70,11 +70,15 @@ struct squashfs_cache_entry *squashfs_cache_get(struct super_block *sb,
 	spin_lock(&cache->lock);
 
 	while (1) {
-		for (i = 0; i < cache->entries; i++)
-			if (cache->entry[i].block == block)
+		for (i = cache->curr_blk, n = 0; n < cache->entries; n++) {
+			if (cache->entry[i].block == block) {
+				cache->curr_blk = i;
 				break;
+			}
+			i = (i + 1) % cache->entries;
+		}
 
-		if (i == cache->entries) {
+		if (n == cache->entries) {
 			/*
 			 * Block not in cache, if all cache entries are used
 			 * go to sleep waiting for one to become available.
@@ -245,6 +249,7 @@ struct squashfs_cache *squashfs_cache_init(char *name, int entries,
 		goto cleanup;
 	}
 
+	cache->curr_blk = 0;
 	cache->next_blk = 0;
 	cache->unused = entries;
 	cache->entries = entries;
diff --git a/fs/squashfs/squashfs_fs_sb.h b/fs/squashfs/squashfs_fs_sb.h
index 651f0b31d296..52934a22f296 100644
--- a/fs/squashfs/squashfs_fs_sb.h
+++ b/fs/squashfs/squashfs_fs_sb.h
@@ -28,6 +28,7 @@
 struct squashfs_cache {
 	char			*name;
 	int			entries;
+	int			curr_blk;
 	int			next_blk;
 	int			num_waiters;
 	int			unused;