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

[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..
For 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.com> 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 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>
>
> --
> 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  http://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