From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 9211C6B0390 for ; Mon, 10 Apr 2017 18:28:20 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id s15so37340164pfi.1 for ; Mon, 10 Apr 2017 15:28:20 -0700 (PDT) Received: from NAM01-SN1-obe.outbound.protection.outlook.com (mail-sn1nam01on0100.outbound.protection.outlook.com. [104.47.32.100]) by mx.google.com with ESMTPS id y18si14758425pgf.390.2017.04.10.15.28.19 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 10 Apr 2017 15:28:19 -0700 (PDT) From: "Zi Yan" Subject: Re: [PATCH] mm, numa: Fix bad pmd by atomically check for pmd_trans_huge when marking page tables prot_numa Date: Mon, 10 Apr 2017 17:28:09 -0500 Message-ID: <789A2322-A5B6-4AC8-8668-D7057A56A140@cs.rutgers.edu> In-Reply-To: <20170410150903.f931ceb5475d2d3d8945bb71@linux-foundation.org> 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> <20170410150903.f931ceb5475d2d3d8945bb71@linux-foundation.org> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=_MailMate_425E350D-C95A-45D1-8D94-39BB13903475_="; micalg=pgp-sha512; protocol="application/pgp-signature" Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Mel Gorman , "Kirill A. Shutemov" , Andrea Arcangeli , Rik van Riel , Michal Hocko , Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 3156 and 4880). --=_MailMate_425E350D-C95A-45D1-8D94-39BB13903475_= Content-Type: text/plain On 10 Apr 2017, at 17:09, Andrew Morton wrote: > 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? thp-fix-madv_dontneed-vs-numa-balancing-race.patch is the fix for numa balancing problem reported in this thread. 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, and thp-fix-madv_dontneed-vs-clear-soft-dirty-race.patch are the fixes for other potential race problems similar to this one. I think it is better to have all these patches applied. -- Best Regards Yan Zi --=_MailMate_425E350D-C95A-45D1-8D94-39BB13903475_= Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- Comment: GPGTools - https://gpgtools.org iQEcBAEBCgAGBQJY7Ab5AAoJEEGLLxGcTqbMqiEH/0vAM87R+aqhF65uHpuGG/VT umngJJY6id0b+mLPWVENFhcUbgYQndpP80oGYCU2bZFptcQq9LdL3jk50G8Vu3MC ciAtKyaxkLA2Fy6cWKDQQ1YY3Mq5knQyFaZ1smjaifeIik5Nr1DR62cOwnugvFly bDWPeGo7jGJbH7s444Zae5SspKc+6PGhyA0ZRuo2iF5PVB9FGJkP3PZkJSQiDckY 79DQ5NZ5zb85Xz2cpjdPmZrthzYPmRlypW1pwhQHbOqgZlj0vhQuEjR0D0/dLmLd LG1TSPfJtPY9R/TAwzTlO8ae1IVe/BA0xdlL+1l5vfJNy9Pz7JXWGCCHDZLOJj4= =LFbh -----END PGP SIGNATURE----- --=_MailMate_425E350D-C95A-45D1-8D94-39BB13903475_=-- -- 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/ . 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