Re: huge improvement with per-device dirty throttling

Andrea Arcangeli
2007-08-22T12:47:37Z

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).