Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752547AbbEYKI5 (ORCPT ); Mon, 25 May 2015 06:08:57 -0400 Received: from mta-out1.inet.fi ([62.71.2.203]:37384 "EHLO jenni1.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752487AbbEYKIT (ORCPT ); Mon, 25 May 2015 06:08:19 -0400 Date: Mon, 25 May 2015 13:05:15 +0300 From: "Kirill A. Shutemov" To: Christoffer Dall Cc: linux-mm@kvack.org, ebru.akagunduz@gmail.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, kirill.shutemov@linux.intel.com, riel@redhat.com, vbabka@suse.cz, zhangyanfei@cn.fujitsu.com, aarcange@redhat.com, Will Deacon , Andre Przywara , Marc Zyngier , linux-arm-kernel@lists.infradead.org Subject: Re: [BUG] Read-Only THP causes stalls (commit 10359213d) Message-ID: <20150525100515.GA8275@node.dhcp.inet.fi> References: <20150524193404.GD16910@cbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150524193404.GD16910@cbox> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1736 Lines: 41 On Sun, May 24, 2015 at 09:34:04PM +0200, Christoffer Dall wrote: > Hi all, > > I noticed a regression on my arm64 APM X-Gene system a couple > of weeks back. I would occassionally see the system lock up and see RCU > stalls during the caching phase of kernbench. I then wrote a small > script that does nothing but cache the files > (http://paste.ubuntu.com/11324767/) and ran that in a loop. On a known > bad commit (v4.1-rc2), out of 25 boots, I never saw it get past 21 > iterations of the loop. I have since tried to run a bisect from v3.19 to > v4.0 using 100 iterations as my criteria for a good commit. > > This resulted in the following first bad commit: > > 10359213d05acf804558bda7cc9b8422a828d1cd > (mm: incorporate read-only pages into transparent huge pages, 2015-02-11) > > Indeed, running the workload on v4.1-rc4 still produced the behavior, > but reverting the above commit gets me through 100 iterations of the > loop. > > I have not tried to reproduce on an x86 system. Turning on a bunch > of kernel debugging features *seems* to hide the problem. My config for > the XGene system is defconfig + CONFIG_BRIDGE and > CONFIG_POWER_RESET_XGENE. > > Please let me know if I can help test patches or other things I can > do to help. I'm afraid that by simply reading the patch I didn't see > anything obviously wrong with it which would cause this behavior. I don't see the problem on x86. Some backtraces could help to track it down. -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/