From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f51.google.com ([74.125.83.51]:35702 "EHLO mail-pg0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751574AbdELTaC (ORCPT ); Fri, 12 May 2017 15:30:02 -0400 Received: by mail-pg0-f51.google.com with SMTP id q125so15067281pgq.2 for ; Fri, 12 May 2017 12:30:02 -0700 (PDT) Date: Fri, 12 May 2017 12:30:00 -0700 From: Omar Sandoval To: Markus Trippelsdorf Cc: linux-block@vger.kernel.org, Omar Sandoval Subject: Re: Kyber scheduler brings system to halt when used on swap partition Message-ID: <20170512193000.GB15267@vader.DHCP.thefacebook.com> References: <20170511125724.GA302@x4> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20170511125724.GA302@x4> Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org On Thu, May 11, 2017 at 02:57:24PM +0200, Markus Trippelsdorf wrote: > Using the new Kyber mq scheduler brings my system to a halt as soon as it > starts swapping. The swap partition resides on an SSD and is the only > partition in use on that drive. > Symptoms are stuttering sound and non moving mouse pointer. After a > while the monitor switches off, because it gets no signal anymore. > At which point only a hard reset will bring the system back. > > "none" works fine. Thanks for testing, I'm taking a look to see if there's anything special about the swap path that would trigger this. In the meantime, if you swapoff your swap partition and do some I/O on it, what happens? Here's a first-order guess at a fio job you could run: fio --group_reporting --filename=$partition \ --name swapin --numjobs=8 --ioengine=sync --rw=randread \ --name swapout --numjobs=4 --ioengine=libaio --iodepth=8 --rw=randwrite Interesting to note is that wbt, which Kyber borrowed ideas from, treats kswapd specially, allowing it to queue more I/O than other processes. I wonder if we need to do the same in Kyber.