Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754437AbcCZVmt (ORCPT ); Sat, 26 Mar 2016 17:42:49 -0400 Received: from mail-wm0-f45.google.com ([74.125.82.45]:38126 "EHLO mail-wm0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754124AbcCZVms (ORCPT ); Sat, 26 Mar 2016 17:42:48 -0400 Subject: Re: [fuse-devel] Horrible mmap write performance (kernel writeback issue?) To: Miklos Szeredi References: <56E7C009.3070008@gmail.com> Cc: fuse-devel , Linux-Fsdevel , Kernel Mailing List From: Jakob Unterwurzacher Message-ID: <56F70255.6070806@gmail.com> Date: Sat, 26 Mar 2016 22:42:45 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1380 Lines: 45 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 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