From: Tejun Heo <htejun@fb.com>
Subject: Re: [PATCH 1/4] sched: move IO scheduling accounting from
 io_schedule_timeout() to __schedule()
Date: Fri, 28 Oct 2016 15:12:32 -0400
Message-ID: <20161028191231.GA29044@htj.duckdns.org>
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Cc: Tejun Heo <tj@kernel.org>, <torvalds@linux-foundation.org>,
        <akpm@linux-foundation.org>, <mingo@redhat.com>, <axboe@kernel.dk>,
        <tytso@mit.edu>, <jack@suse.com>, <adilger.kernel@dilger.ca>,
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To: Peter Zijlstra <peterz@infradead.org>
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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