Horrible btrfs performance on cold cache

Horrible btrfs performance on cold cache

[Felipe Contreras]

Hi,

I use btrfs on most of my volumes on my laptop, and I've always felt
booting was very slow, but definitely sure is slow, is starting up
Google Chrome:

encrypted ext4: ~20s
btrfs: ~2:11s

I have tried different things to find out exactly what is the issue,
but haven't quite found it yet.

Here's some stuff I got from latencytop, not sure if would be helpful:

4969.1ms
sys_mmap_pgoff
syscall_call
(chrome)

1139.9ms
sync_page
sync_page_killable
__lock_page_killable
generic_file_aio_read
do_sync_read
vfs_read
sys_read
sysenter_do_call
(chrome)

431.9ms
sync_page
wait_on_page_bit
read_extent_buffer_pages
btree_read_extent_buffer_pages
read_tree_block
read_block_for_search
btrfs_search_slot
lookup_inline_extent_backref
__btrfs_free_extent
run_clustered_refs
btrfs_run_delayed_refs
btrfs_commit_transaction
(btrfs)

Cheers.

-- 
Felipe Contreras

Re: Horrible btrfs performance on cold cache

[Calvin Walton]

On Mon, 2010-10-11 at 03:30 +0300, Felipe Contreras wrote:
> Hi,
> 
> I use btrfs on most of my volumes on my laptop, and I've always felt
> booting was very slow, but definitely sure is slow, is starting up
> Google Chrome:
> 
> encrypted ext4: ~20s
> btrfs: ~2:11s
> 
> I have tried different things to find out exactly what is the issue,
> but haven't quite found it yet.

If you've been using this volume for a while, it could just have become
badly fragmented. You could try btrfs's fancy online defragmentation
abilities to see if that'll give you an improvement:

# btrfs filesystem defragment /mountpoint/of/volume

Let us know if that helps, of course :)

-- 
Calvin Walton <calvin.walton@gmail.com>

Re: Horrible btrfs performance on cold cache

[Chester]

I think I read/heard somewhere that snapshots can cause pretty bad
fragmentation, because it causes your system to write changes to files
to random locations on the disk, leaving the original inodes intact..
=46or that reason, I have replaced the directories ~/.config/chromium ,
/var , /usr/portage with subvolumes, so they will not be included in
snapshots.

It seems like chromium opens much quicker now, but it's still a long
way from what it was on ext4

On Mon, Oct 11, 2010 at 10:46 AM, Calvin Walton <calvin.walton@gmail.co=
m> wrote:
>
> On Mon, 2010-10-11 at 03:30 +0300, Felipe Contreras wrote:
> > Hi,
> >
> > I use btrfs on most of my volumes on my laptop, and I've always fel=
t
> > booting was very slow, but definitely sure is slow, is starting up
> > Google Chrome:
> >
> > encrypted ext4: ~20s
> > btrfs: ~2:11s
> >
> > I have tried different things to find out exactly what is the issue=
,
> > but haven't quite found it yet.
>
> If you've been using this volume for a while, it could just have beco=
me
> badly fragmented. You could try btrfs's fancy online defragmentation
> abilities to see if that'll give you an improvement:
>
> # btrfs filesystem defragment /mountpoint/of/volume
>
> Let us know if that helps, of course :)
>
> --
> Calvin Walton <calvin.walton@gmail.com>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs=
" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at =A0http://vger.kernel.org/majordomo-info.html

Re: Horrible btrfs performance on cold cache

[Felipe Contreras]

On Mon, Oct 11, 2010 at 7:23 PM, Chester <somethingsome2000@gmail.com> wrote:
> I think I read/heard somewhere that snapshots can cause pretty bad
> fragmentation

But I'm not using snapshots.

-- 
Felipe Contreras

Re: Horrible btrfs performance on cold cache

[Felipe Contreras]

On Mon, Oct 11, 2010 at 6:46 PM, Calvin Walton <calvin.walton@gmail.com> wrote:
> On Mon, 2010-10-11 at 03:30 +0300, Felipe Contreras wrote:
>> I use btrfs on most of my volumes on my laptop, and I've always felt
>> booting was very slow, but definitely sure is slow, is starting up
>> Google Chrome:
>>
>> encrypted ext4: ~20s
>> btrfs: ~2:11s
>>
>> I have tried different things to find out exactly what is the issue,
>> but haven't quite found it yet.
>
> If you've been using this volume for a while, it could just have become
> badly fragmented. You could try btrfs's fancy online defragmentation
> abilities to see if that'll give you an improvement:
>
> # btrfs filesystem defragment /mountpoint/of/volume
>
> Let us know if that helps, of course :)

~2:06s, so it helped a bit, but not much really, there's still
something fishy going on.

-- 
Felipe Contreras