From: Jens Axboe <axboe@kernel.dk>
To: Tejun Heo <tj@kernel.org>
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
Date: Thu, 16 Jul 2015 09:02:56 -0600 [thread overview]
Message-ID: <55A7C7A0.9050907@kernel.dk> (raw)
In-Reply-To: <20150716145919.GV15934@mtj.duckdns.org>
On 07/16/2015 08:59 AM, Tejun Heo wrote:
> 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?
Right, that's where it's called in the fast path. Right now, it's
per-jiffy lazy. As to how/when it's called, I don't believe that has
changed since those stats were introduced. If we can move that out of
the fast path, then the percpu changes are straight forward.
--
Jens Axboe
next prev parent reply other threads:[~2015-07-16 15:02 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-16 3:16 [PATCH 0/4] block: account io: kill atomic operations Ming Lei
2015-07-16 3:16 ` [PATCH 1/4] block: partition: introduce hd_free_part() Ming Lei
2015-07-16 3:16 ` [PATCH 2/4] block: partition: convert percpu ref Ming Lei
2015-07-16 14:36 ` Tejun Heo
2015-07-16 3:16 ` [PATCH 3/4] block: partition: introduce 'cpu' para to part_inc|dec_in_flight Ming Lei
2015-07-16 3:16 ` [PATCH 4/4] block: account io: convert part->in_fligh[] into percpu variable Ming Lei
2015-07-16 14:40 ` Tejun Heo
2015-07-16 14:48 ` [PATCH 0/4] block: account io: kill atomic operations Jens Axboe
2015-07-16 14:59 ` Tejun Heo
2015-07-16 15:02 ` Jens Axboe [this message]
2015-07-16 15:01 ` Ming Lei
2015-07-16 15:09 ` Jens Axboe
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