From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752906AbdDJWJF (ORCPT ); Mon, 10 Apr 2017 18:09:05 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:59360 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752108AbdDJWJE (ORCPT ); Mon, 10 Apr 2017 18:09:04 -0400 Date: Mon, 10 Apr 2017 15:09:03 -0700 From: Andrew Morton To: Mel Gorman Cc: Zi Yan , "Kirill A. Shutemov" , Andrea Arcangeli , Rik van Riel , Michal Hocko , Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm, numa: Fix bad pmd by atomically check for pmd_trans_huge when marking page tables prot_numa Message-Id: <20170410150903.f931ceb5475d2d3d8945bb71@linux-foundation.org> In-Reply-To: <20170410180714.7yfnxl7qin72jcob@techsingularity.net> References: <20170410094825.2yfo5zehn7pchg6a@techsingularity.net> <84B5E286-4E2A-4DE0-8351-806D2102C399@cs.rutgers.edu> <20170410172056.shyx6qzcjglbt5nd@techsingularity.net> <8A6309F4-DB76-48FA-BE7F-BF9536A4C4E5@cs.rutgers.edu> <20170410180714.7yfnxl7qin72jcob@techsingularity.net> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 10 Apr 2017 19:07:14 +0100 Mel Gorman wrote: > On Mon, Apr 10, 2017 at 12:49:40PM -0500, Zi Yan wrote: > > On 10 Apr 2017, at 12:20, Mel Gorman wrote: > > > > > On Mon, Apr 10, 2017 at 11:45:08AM -0500, Zi Yan wrote: > > >>> While this could be fixed with heavy locking, it's only necessary to > > >>> make a copy of the PMD on the stack during change_pmd_range and avoid > > >>> races. A new helper is created for this as the check if quite subtle and the > > >>> existing similar helpful is not suitable. This passed 154 hours of testing > > >>> (usually triggers between 20 minutes and 24 hours) without detecting bad > > >>> PMDs or corruption. A basic test of an autonuma-intensive workload showed > > >>> no significant change in behaviour. > > >>> > > >>> Signed-off-by: Mel Gorman > > >>> Cc: stable@vger.kernel.org > > >> > > >> Does this patch fix the same problem fixed by Kirill's patch here? > > >> https://lkml.org/lkml/2017/3/2/347 > > >> > > > > > > I don't think so. The race I'm concerned with is due to locks not being > > > held and is in a different path. > > > > I do not agree. Kirill's patch is fixing the same race problem but in > > zap_pmd_range(). > > > > The original autoNUMA code first clears PMD then sets it to protnone entry. > > pmd_trans_huge() does not return TRUE because it saw cleared PMD, but > > pmd_none_or_clear_bad() later saw the protnone entry and reported it as bad. > > Is this the problem you are trying solve? > > > > Kirill's patch will pmdp_invalidate() the PMD entry, which keeps _PAGE_PSE bit, > > so pmd_trans_huge() will return TRUE. In this case, it also fixes > > your race problem in change_pmd_range(). > > > > Let me know if I miss anything. > > > > Ok, now I see. I think you're correct and I withdraw the patch. I have Kirrill's thp-reduce-indentation-level-in-change_huge_pmd.patch thp-fix-madv_dontneed-vs-numa-balancing-race.patch mm-drop-unused-pmdp_huge_get_and_clear_notify.patch thp-fix-madv_dontneed-vs-madv_free-race.patch thp-fix-madv_dontneed-vs-madv_free-race-fix.patch thp-fix-madv_dontneed-vs-clear-soft-dirty-race.patch scheduled for 4.12-rc1. It sounds like thp-fix-madv_dontneed-vs-madv_free-race.patch and thp-fix-madv_dontneed-vs-madv_free-race.patch need to be boosted to 4.11 and stable?