Date: Thu, 16 Jul 2015 10:59:19 -0400
From: Tejun Heo <tj@kernel.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: Ming Lei <tom.leiming@gmail.com>, linux-kernel@vger.kernel.org,
        Mike Snitzer <snitzer@redhat.com>
Subject: Re: [PATCH 0/4] block: account io: kill atomic operations
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On Thu, Jul 16, 2015 at 08:48:41AM -0600, Jens Axboe wrote:
> I've played with this before, but always ran into the hurdle of making
> part_in_flight() too expensive ended up hurting results in the end. Making
> the inc/dec parts of accounting percpu is a no-brainer, unfortunately the
> summing then becomes pretty expensive. I'll run this through some testing
> and see what kind of results I get.

The only place which could be a problem is part_round_stats() and we
can do that *way* lazier.  I don't think we're using that internally.
Why are we even invoking it from IO issue / completion path?

Thanks.

-- 
tejun
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