On Mon, Apr 09, 2012 at 01:10:04PM -0400, Calvin Walton wrote:
> On Mon, 2012-04-09 at 11:53 -0400, Calvin Walton wrote:
> > Hi,
> >
> > I have a system that's using a dracut-generated initramfs to mount a
> > btrfs root. After upgrading to kernel 3.4.0-rc2 to test it out, I've
> > noticed that the process of mounting the root filesystem takes much
> > longer with 3.4.0-rc2 than it did with 3.3.1 - nearly 30 seconds slower!
> >
> > Does anyone have any ideas? I'm going to try bisecting the issue to see
> > if I can narrow down the cause. I've included excerpts from dmesg of the
> > bad and good kernels here, and attached the complete dmesg from the bad
> > kernel, in case it has anything interesting that I've trimmed out here.
>
> And the bisect results are in:
> 285ff5af6ce358e73f53b55c9efadd4335f4c2ff is the first bad commit
> commit 285ff5af6ce358e73f53b55c9efadd4335f4c2ff
> Author: Josef Bacik <josef@xxxxxxxxxx>
> Date: Fri Jan 13 15:27:45 2012 -0500
>
> Btrfs: remove the ideal caching code
>
> This is a relic from before we had the disk space cache and it was to make
> bootup times when you had btrfs as root not be so damned slow. Now that we have
> the disk space cache this isn't a problem anymore and really having this code
> casues uneeded fragmentation and complexity, so just remove it. Thanks,
>
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxx>
>
> The commit doesn't revert cleanly on top of 3.4.0-rc2, so I haven't
> tested that; but it looks like that caching code is in fact still useful
> to make "btrfs as root not be so damned slow."
>
Ok can you give this a whirl? You are going to have to boot/reboot a few times
to let the cache get re-generated again to make sure it's taken effect, but
hopefully this will help out. Thanks,
Josef
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index a844204..7a703d2 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -530,8 +530,8 @@ static int cache_block_group(struct btrfs_block_group_cache *cache,
* we likely hold important locks.
*/
if (trans && (!trans->transaction->in_commit) &&
- (root && root != root->fs_info->tree_root) &&
- btrfs_test_opt(root, SPACE_CACHE)) {
+ root != fs_info->tree_root &&
+ fs_info->mount_opt & BTRFS_MOUNT_SPACE_CACHE) {
ret = load_free_space_cache(fs_info, cache);
spin_lock(&cache->lock);
--
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