linux-kernel - Re: [PATCH 2/6] blkcg: add blkg_[rw]stat->aux_cnt and replace cfq_group->dead

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Message-ID: <20150626133540.GA15805@mtj.duckdns.org>
Date:	Fri, 26 Jun 2015 09:35:40 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	axboe@...nel.dk, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org, avanzini.arianna@...il.com,
	kernel-team@...com
Subject: Re: [PATCH 2/6] blkcg: add blkg_[rw]stat->aux_cnt and replace
 cfq_group->dead_stats with it

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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