From: Peter Zijlstra Subject: Re: [PATCH 1/4] sched: move IO scheduling accounting from io_schedule_timeout() to __schedule() Date: Sat, 29 Oct 2016 05:21:26 +0200 Message-ID: <20161029032126.GH3568@worktop.programming.kicks-ass.net> References: <1477673892-28940-1-git-send-email-tj@kernel.org> <1477673892-28940-2-git-send-email-tj@kernel.org> <20161028182712.GM3142@twins.programming.kicks-ass.net> <20161028190702.GL3157@twins.programming.kicks-ass.net> <20161028191231.GA29044@htj.duckdns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Tejun Heo , torvalds@linux-foundation.org, akpm@linux-foundation.org, mingo@redhat.com, axboe@kernel.dk, tytso@mit.edu, jack@suse.com, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, mingbo@fb.com To: Tejun Heo Return-path: Content-Disposition: inline In-Reply-To: <20161028191231.GA29044@htj.duckdns.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Fri, Oct 28, 2016 at 03:12:32PM -0400, Tejun Heo wrote: > 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 This one I actually fixed and should be in -next. And it would be sufficient to cover the use case here. > 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. rwsems could be done for writers only.