jffs2: Dynamically choose inocache hash size
When JFFS2 is used for large volumes, the mount times are quite long.
Increasing the hash size provides a significant speed boost on the OLPC
XO-1 laptop.
Add logic that dynamically selects a hash size based on the size of
the medium. A 64mb medium will result in a hash size of 128, and a 512mb
medium will result in a hash size of 1024.
Signed-off-by: Daniel Drake <dsd@laptop.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/fs/jffs2/fs.c b/fs/jffs2/fs.c
index 6b2964a..2701b37 100644
--- a/fs/jffs2/fs.c
+++ b/fs/jffs2/fs.c
@@ -478,6 +478,25 @@
return inode;
}
+static int calculate_inocache_hashsize(uint32_t flash_size)
+{
+ /*
+ * Pick a inocache hash size based on the size of the medium.
+ * Count how many megabytes we're dealing with, apply a hashsize twice
+ * that size, but rounding down to the usual big powers of 2. And keep
+ * to sensible bounds.
+ */
+
+ int size_mb = flash_size / 1024 / 1024;
+ int hashsize = (size_mb * 2) & ~0x3f;
+
+ if (hashsize < INOCACHE_HASHSIZE_MIN)
+ return INOCACHE_HASHSIZE_MIN;
+ if (hashsize > INOCACHE_HASHSIZE_MAX)
+ return INOCACHE_HASHSIZE_MAX;
+
+ return hashsize;
+}
int jffs2_do_fill_super(struct super_block *sb, void *data, int silent)
{
@@ -524,7 +543,8 @@
if (ret)
return ret;
- c->inocache_list = kcalloc(INOCACHE_HASHSIZE, sizeof(struct jffs2_inode_cache *), GFP_KERNEL);
+ c->inocache_hashsize = calculate_inocache_hashsize(c->flash_size);
+ c->inocache_list = kcalloc(c->inocache_hashsize, sizeof(struct jffs2_inode_cache *), GFP_KERNEL);
if (!c->inocache_list) {
ret = -ENOMEM;
goto out_wbuf;