Re: [RFC] writeback and cgroup

From: Fengguang Wu
Date: Sun Apr 22 2012 - 10:32:14 EST

On Fri, Apr 20, 2012 at 02:33:01PM -0700, Tejun Heo wrote:
> On Fri, Apr 20, 2012 at 03:29:30PM -0400, Vivek Goyal wrote:
> > I am personally is not too excited about the case of putting async IO
> > in separate groups due to the reason that async IO of one group will
> > start impacting latencies of sync IO of another group and in practice
> > it might not be desirable. But there are others who have use cases for
> > separate async IO queue. So as long as switch is there to change the
> > behavior, I am not too worried.
> Why not just fix cfq so that it prefers groups w/ sync IOs?

There may be a sync+async group in front, but when switch into it, it
decides to give its async queue a run. That's not necessarily a bad
decision, but we do lose some control here.
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