From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f179.google.com (mail-wi0-f179.google.com [209.85.212.179]) by kanga.kvack.org (Postfix) with ESMTP id 377046B00AC for ; Mon, 25 May 2015 06:05:30 -0400 (EDT) Received: by wizk4 with SMTP id k4so43495173wiz.1 for ; Mon, 25 May 2015 03:05:29 -0700 (PDT) Received: from jenni1.inet.fi (mta-out1.inet.fi. [62.71.2.195]) by mx.google.com with ESMTP id em3si11788633wib.90.2015.05.25.03.05.28 for ; Mon, 25 May 2015 03:05:28 -0700 (PDT) Date: Mon, 25 May 2015 13:05:15 +0300 From: "Kirill A. Shutemov" 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org