linux-kernel - Re: [PATCH 6/6] blk-mq: remove REQ_ATOM

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Message-ID: <20171212172908.GG3919388@devbig577.frc2.facebook.com>
Date:   Tue, 12 Dec 2017 09:29:08 -0800
From:   Tejun Heo <tj@...nel.org>
To:     Nikolay Borisov <nborisov@...e.com>
Cc:     axboe@...nel.dk, linux-kernel@...r.kernel.org, oleg@...hat.com,
        peterz@...radead.org, kernel-team@...com, osandov@...com
Subject: Re: [PATCH 6/6] blk-mq: remove REQ_ATOM_STARTED

Hello, Nikolay.

On Tue, Dec 12, 2017 at 01:17:52PM +0200, Nikolay Borisov wrote:
> On  9.12.2017 21:25, Tejun Heo wrote:
> > After the recent updates to use generation number and state based
> > synchronization, we can easily replace REQ_ATOM_STARTED usages by
> > adding an extra state to distinguish completed but not yet freed
> > state.
> > 
> > Add MQ_RQ_COMPLETE and replace REQ_ATOM_STARTED usages with
> > blk_mq_rq_state() tests.  REQ_ATOM_STARTED no longer has any users
> > left and is removed.
> 
> Where are the promised in patch 5/6 performance results?

Opos, I thought I removed all of those.  I couldn't reliably show that
this performed better.  I was testing with nullblk but the run-to-run
deviations were too great (they generally kept getting faster, maybe
better locality?) to draw a reliable conclusion.  Whatever difference
in performance is unlikely to be material in actual workloads anyway.

I dropped the sentence from the description.

Thanks.

-- 
tejun