Re: [PATCH 2/6] blkcg: add blkg_[rw]stat->aux_cnt and replace cfq_group->dead_stats with it

From: Tejun Heo
Date: Fri Jun 26 2015 - 09:35:54 EST


On Fri, Jun 26, 2015 at 09:27:02AM -0400, Vivek Goyal wrote:
> On Thu, Jun 25, 2015 at 05:38:53PM -0400, Tejun Heo wrote:
>
> [..]
> > It's planned that the core stats will be moved to blkcg_gq, so we want
> > to move the mechanism for keeping track of the stats of dead children
> > from cfq to blkcg core. This patch adds blkg_[rw]stat->aux_cnt which
> > are atomic64_t's keeping track of auxiliary counts which are excluded
> > when reading local counts but included for recursive.
>
> Hi Tejun,
>
> So aux_cnt is atomic64_t as updation is not the hot path hence there is
> not much value in keeping it as per cpu?

I'm not following. aux_cnt isn't per-cpu.

Thanks.

--
tejun
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