linux-ext4 - Re: [PATCH 1/4] sched: move IO scheduling accounting from io_schedule_timeout() to _

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Message-ID: <20161028191231.GA29044@htj.duckdns.org>
Date:   Fri, 28 Oct 2016 15:12:32 -0400
From:   Tejun Heo <htejun@...com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     Tejun Heo <tj@...nel.org>, <torvalds@...ux-foundation.org>,
        <akpm@...ux-foundation.org>, <mingo@...hat.com>, <axboe@...nel.dk>,
        <tytso@....edu>, <jack@...e.com>, <adilger.kernel@...ger.ca>,
        <linux-ext4@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <kernel-team@...com>,
        <mingbo@...com>
Subject: Re: [PATCH 1/4] sched: move IO scheduling accounting from
 io_schedule_timeout() to __schedule()

Hello, Peter.

On Fri, Oct 28, 2016 at 09:07:02PM +0200, Peter Zijlstra wrote:
> One alternative is to inherit the iowait state of the task we block on.
> That'll not get rid of the branches much, but it will remove the new
> mutex APIs.

Yeah, thought about that briefly but we don't necessarily track mutex
or other synchronization construct owners, things get gnarly with
rwsems (the inode ones sometimes end up in a similar situation), and
we'll probably end up dealing with some surprising propagations down
the line.  That said, getting such automatic propagation working would
be great.

Thanks.

-- 
tejun
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