Re: Abysmal Performance

[Henning Rohlfs <x+@xehonk.de>]

 On Tue, 21 Jun 2011 11:18:30 -0400, Josef Bacik wrote:
> On 06/21/2011 05:26 AM, Henning Rohlfs wrote:
>> On Tue, 21 Jun 2011 10:00:59 +0200, Sander wrote:
>>> Henning Rohlfs wrote (ao):
>>>> - space_cache was enabled, but it seemed to make the problem 
>>>> worse.
>>>> It's no longer in the mount options.
>>>
>>> space_cache is a one time mount option which enabled space_cache. 
>>> Not
>>> supplying it anymore as a mount option has no effect (dmesg | grep
>>> btrfs).
>>
>> I'm sure that after the first reboot after removing the flag from 
>> the
>> mount options, the system was faster for a while. That must have 
>> been a
>> coincidence (or just an error on my part).
>>
>
> No, the space cache will make your system faster _after_ having been
> enabled once. The reason for this is because we have to build the 
> cache
> the slow way at first, and then after that we can do it the fast way.
> What is probably happening is your box is slowing down trying to 
> build
> this cache.  Don't mount with clear_cache unless there is a bug in 
> your
> cache.  Let it do it's thing and stuff will get faster.

 I'm just reporting what I experienced. I had space_cache in the mount 
 options while the problem developed and removed it when the system got 
 too slow. After the next reboot the system was responsive for a short 
 time (an hour maybe - which seems to have been unrelated to the mount 
 option though from what you described). Now there's no difference 
 whatsoever between no options, space_cache and clear_cache.

 To sum it up: I only played with the clear_cache option because the 
 system got too slow in the first place. I don't see how the problem can 
 be related to this option if changing it it makes no difference.

 Thanks,
 Henning