Re: huge improvement with per-device dirty throttling

Leroy van Logchem
2007-09-04T09:37:36Z

Andrea Arcangeli wrote:
> On Wed, Aug 22, 2007 at 01:05:13PM +0200, Andi Kleen wrote:
>> Ok perhaps the new adaptive dirty limits helps your single disk
>> a lot too. But your improvements seem to be more "collateral damage" @)
>>
>> But if that was true it might be enough to just change the dirty limits
>> to get the same effect on your system. You might want to play with
>> /proc/sys/vm/dirty_*
>
> The adaptive dirty limit is per task so it can't be reproduced with
> global sysctl. It made quite some difference when I researched into it
> in function of time. This isn't in function of time but it certainly
> makes a lot of difference too, actually it's the most important part
> of the patchset for most people, the rest is for the corner cases that
> aren't handled right currently (writing to a slow device with
> writeback cache has always been hanging the whole thing).

Self-tuning > static sysctl's. The last years we needed to use very
small values for dirty_ratio and dirty_background_ratio to soften the
latency problems we have during sustained writes. Imo these patches
really help in many cases, please commit to mainline.

--
Leroy