Re: extremely slow syncing on btrfs with 2.6.39.1

[Lubos Kolouch <lubos.kolouch@xxxxxxxxx>]

Jan Stilow, Tue, 12 Jul 2011 09:18:06 +0200:

> On 07/11/2011 02:18 AM, Kok, Auke-jan H wrote:
>> I've been monitoring the lists for a while now but didn't see this
>> problem mentioned in particular: I've got a fairly standard desktop
>> system at home, 700gb WD drive, nothing special, with 2 btrfs
>> filesystems and some snapshots. The system runs for days, and I've
>> noticed unusual disk activity the other evening - turns out that it's
>> taking forever to sync().
>> 
>> $ uname -r
>> 2.6.39.1
>> $ grep btrfs /proc/mounts
>> /dev/root / btrfs rw,relatime 0 0    # is /dev/sdb2 # /dev/sdb5 /home
>> btrfs rw,relatime 0 0 $ time sync
>> 
>> real	1m5.552s
>> user	0m0.000s
>> sys	0m2.102s
>> 
>> $ time sync
>> 
>> real	1m16.830s
>> user	0m0.001s
>> sys	0m1.490s
>> 
>> $ df -h / /home
>> Filesystem      Size  Used Avail Use% Mounted on /dev/root        47G  
>> 33G  7.7G  82% / /dev/sdb5       652G  216G  421G  34% /home $ btrfs fi
>> df /
>> Data: total=35.48GB, used=29.86GB
>> System, DUP: total=16.00MB, used=12.00KB System: total=4.00MB,
>> used=0.00
>> Metadata, DUP: total=4.50GB, used=1.67GB
>>  $ btrfs fi df /home
>> Data: total=310.01GB, used=209.53GB
>> System, DUP: total=8.00MB, used=48.00KB System: total=4.00MB, used=0.00
>> Metadata, DUP: total=11.00GB, used=2.98GB Metadata: total=8.00MB,
>> used=0.00
>> 
>> I'll switch to 3.0 soon, but, given the fact that we're going to be
>> running MeeGo on 2.6.39 probably for a while, I was wondering if anyone
>> knows off the top of their heads if this issue is known/identified. If
>> not then I'll need to make someone do some patching ;).
>> 
>> Auke
> 
> You should read the thread "Abysmal Performance" of these mailing list
> from last month. They had a similar problem and downgraded to a 2.6.38
> kernel. By the way, that works for me too for the time being.
> 
> Best Regards.
> 
> Jan Stilow

I had similar experience with two servers running on 2.6.39 - the 
performance was terrible, after downgrade to 2.6.38 the speed is OK again.

Best regards

Lubos Kolouch

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