Re: [PATCHSET] blkcg: unify blkgs for different policies

From: Tejun Heo
Date: Thu Feb 02 2012 - 15:36:12 EST


On Thu, Feb 02, 2012 at 02:29:58PM -0500, Vivek Goyal wrote:
> On Wed, Feb 01, 2012 at 01:19:05PM -0800, Tejun Heo wrote:
> [..]
> >
> > * use unified stats updated under queue lock and drop percpu stats
> > which should fix locking / context bug across percpu allocation.
> Does that mean that stat updation will happen under queue lock even if
> there are no throttling rules? That will introduce extra queue lock on
> fast path those who have throttling compiled in but are not using (common
> case for distributions).

No, I don't think extra locking would be necessary at all. We end up
grabbing queue_lock anyway. It's just the matter of where to update
the stats.


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