Re: [PATCH 18/23] io-controller: blkio_cgroup patches from Ryo to track async bios.

From: Balbir Singh
Date: Tue Sep 01 2009 - 23:12:46 EST

On Wed, Sep 2, 2009 at 6:29 AM, KAMEZAWA
Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> On Tue, 1 Sep 2009 10:11:42 -0400
> Vivek Goyal <vgoyal@xxxxxxxxxx> wrote:
>> > > > - Somebody also gave an example where there is a memory hogging process and
>> > > >  possibly pushes out some processes to swap. It does not sound fair to
>> > > >  charge those proccess for that swap writeout. These processes never
>> > > >  requested swap IO.
>> >
>> > I think that swap writeouts should be charged to the memory hogging
>> > process, because the process consumes more resources and it should get
>> > a penalty.
>> >
>> A process requesting memory gets IO penalty? IMHO, swapping is a kernel
>> mechanism and kernel's way of providing extended RAM. If we want to solve
>> the issue of memory hogging by a process then right way to solve is to use
>> memory controller and not by charging the process for IO activity.
>> Instead, proabably a more suitable way is to charge swap activity to root
>> group (where by default all the kernel related activity goes).
> I agree. It't memcg's job.
> (Support dirty_ratio in memcg is necessary, I think)
> background-write-out-to-swap-for-memory-shortage should be handled
> as kernel I/O. If swap-out-by-memcg bacause of its limit is a problem,
> dirty_ratio for memcg should be implemetned.

I tend to agree, looks like dirty_ratio will become important along
with overcommit support in the future.

Balbir Singh.
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