Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755377AbcC1Tp4 (ORCPT ); Mon, 28 Mar 2016 15:45:56 -0400 Received: from mail-ob0-f195.google.com ([209.85.214.195]:33303 "EHLO mail-ob0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754127AbcC1Tpy (ORCPT ); Mon, 28 Mar 2016 15:45:54 -0400 MIME-Version: 1.0 X-Originating-IP: [217.173.44.24] In-Reply-To: <56F70255.6070806@gmail.com> References: <56E7C009.3070008@gmail.com> <56F70255.6070806@gmail.com> Date: Mon, 28 Mar 2016 21:45:53 +0200 Message-ID: Subject: Re: [fuse-devel] Horrible mmap write performance (kernel writeback issue?) From: Miklos Szeredi To: Jakob Unterwurzacher Cc: fuse-devel , Linux-Fsdevel , Kernel Mailing List , Tejun Heo Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1688 Lines: 60 On Sat, Mar 26, 2016 at 10:42 PM, Jakob Unterwurzacher wrote: > On 16.03.2016 10:44, Miklos Szeredi wrote: >> On Tue, Mar 15, 2016 at 8:55 AM, Jakob Unterwurzacher >> wrote: >>> Just for anybody finding this thread: This still happens in v4.4, it >>> just took longer to trigger. >>> >>> I have posted more details to linux-kernel (copy-pasted below), >>> http://thread.gmane.org/gmane.linux.kernel/2132944 >> >> Okay, so you can reproduce this relatively quickly. Can you try "git >> bisect" to find exactly which commit is responsible? >> >> Thanks, >> Miklos > > That took a while, but it looks like it got it: > >> commit 947e9762a8ddefda38aa21e249e6a4fec215cd12 >> Author: Tejun Heo >> Date: Fri May 22 18:23:32 2015 -0400 >> >> writeback: update wb_over_bg_thresh() to use wb_domain aware operations > Tejun, Any idea why this commit stalls fuse mmap writes? Here's the start of the this thread: http://marc.info/?l=fuse-devel&m=145008058603261&w=2 Thanks, Miklos > Note that this commens seems to only activate changes that happened in the > commit before, aa661bb: > >> commit aa661bbe1e61ce80ca4ae98804f673ede94b0827 >> Author: Tejun Heo >> Date: Fri May 22 18:23:31 2015 -0400 >> >> writeback: move over_bground_thresh() to mm/page-writeback.c > > > Anyway, I can reliably reboot between aa661bb and 947e976 and always get the > same results: > > aa661bb passes > 947e976 fails > > I you want to reproduce, clone https://github.com/rfjakob/mmapwrite.git and > run ./encfs-test.sh (needs encfs installed). On the bad kernel, it will hang > within a few seconds. > > Thanks, > Jakob