From: Rik van Riel <riel@redhat.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Alex Thorlton <athorlton@sgi.com>, Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
hhuang@redhat.com
Subject: Re: [PATCH 14/15] mm: numa: Flush TLB if NUMA hinting faults race with PTE scan update
Date: Thu, 05 Dec 2013 15:05:19 -0500 [thread overview]
Message-ID: <52A0DC7F.7050403@redhat.com> (raw)
In-Reply-To: <20131205195446.GI11295@suse.de>
On 12/05/2013 02:54 PM, Mel Gorman wrote:
> I think that's a better fit and a neater fix. Thanks! I think it barriers
> more than it needs to (definite cost vs maybe cost), the flush can be
> deferred until we are definitely trying to migrate and the pte case is
> not guaranteed to be flushed before migration due to pte_mknonnuma causing
> a flush in ptep_clear_flush to be avoided later. Mashing the two patches
> together yields this.
I think this would fix the numa migrate case.
However, I believe the same issue is also present in
mprotect(..., PROT_NONE) vs. compaction, for programs
that trap SIGSEGV for garbage collection purposes.
They could lose modifications done in-between when
the pte was set to PROT_NONE, and the actual TLB
flush, if compaction moves the page around in-between
those two events.
I don't know if this is a case we need to worry about
at all, but I think the same fix would apply to that
code path, so I guess we might as well make it...
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WARNING: multiple messages have this Message-ID (diff)
From: Rik van Riel <riel@redhat.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Alex Thorlton <athorlton@sgi.com>, Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
hhuang@redhat.com
Subject: Re: [PATCH 14/15] mm: numa: Flush TLB if NUMA hinting faults race with PTE scan update
Date: Thu, 05 Dec 2013 15:05:19 -0500 [thread overview]
Message-ID: <52A0DC7F.7050403@redhat.com> (raw)
In-Reply-To: <20131205195446.GI11295@suse.de>
On 12/05/2013 02:54 PM, Mel Gorman wrote:
> I think that's a better fit and a neater fix. Thanks! I think it barriers
> more than it needs to (definite cost vs maybe cost), the flush can be
> deferred until we are definitely trying to migrate and the pte case is
> not guaranteed to be flushed before migration due to pte_mknonnuma causing
> a flush in ptep_clear_flush to be avoided later. Mashing the two patches
> together yields this.
I think this would fix the numa migrate case.
However, I believe the same issue is also present in
mprotect(..., PROT_NONE) vs. compaction, for programs
that trap SIGSEGV for garbage collection purposes.
They could lose modifications done in-between when
the pte was set to PROT_NONE, and the actual TLB
flush, if compaction moves the page around in-between
those two events.
I don't know if this is a case we need to worry about
at all, but I think the same fix would apply to that
code path, so I guess we might as well make it...
next prev parent reply other threads:[~2013-12-05 20:05 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-03 8:51 [PATCH 00/14] NUMA balancing segmentation faults candidate fix on large machines Mel Gorman
2013-12-03 8:51 ` Mel Gorman
2013-12-03 8:51 ` [PATCH 01/15] mm: numa: Do not batch handle PMD pages Mel Gorman
2013-12-03 8:51 ` Mel Gorman
2013-12-03 8:51 ` [PATCH 02/15] mm: hugetlbfs: fix hugetlbfs optimization Mel Gorman
2013-12-03 8:51 ` Mel Gorman
2013-12-03 8:51 ` [PATCH 03/15] mm: thp: give transparent hugepage code a separate copy_page Mel Gorman
2013-12-03 8:51 ` Mel Gorman
2013-12-04 16:59 ` Alex Thorlton
2013-12-04 16:59 ` Alex Thorlton
2013-12-05 13:35 ` Mel Gorman
2013-12-05 13:35 ` Mel Gorman
2013-12-03 8:51 ` [PATCH 04/15] mm: numa: Serialise parallel get_user_page against THP migration Mel Gorman
2013-12-03 8:51 ` Mel Gorman
2013-12-03 23:07 ` Rik van Riel
2013-12-03 23:07 ` Rik van Riel
2013-12-03 23:54 ` Mel Gorman
2013-12-03 23:54 ` Mel Gorman
2013-12-03 8:51 ` [PATCH 05/15] mm: numa: Call MMU notifiers on " Mel Gorman
2013-12-03 8:51 ` Mel Gorman
2013-12-03 8:51 ` [PATCH 06/15] mm: Clear pmd_numa before invalidating Mel Gorman
2013-12-03 8:51 ` Mel Gorman
2013-12-03 8:51 ` [PATCH 07/15] mm: numa: Do not clear PMD during PTE update scan Mel Gorman
2013-12-03 8:51 ` Mel Gorman
2013-12-03 8:51 ` [PATCH 08/15] mm: numa: Do not clear PTE for pte_numa update Mel Gorman
2013-12-03 8:51 ` Mel Gorman
2013-12-03 8:51 ` [PATCH 09/15] mm: numa: Ensure anon_vma is locked to prevent parallel THP splits Mel Gorman
2013-12-03 8:51 ` Mel Gorman
2013-12-03 8:51 ` [PATCH 10/15] mm: numa: Avoid unnecessary work on the failure path Mel Gorman
2013-12-03 8:51 ` Mel Gorman
2013-12-03 8:51 ` [PATCH 11/15] sched: numa: Skip inaccessible VMAs Mel Gorman
2013-12-03 8:51 ` Mel Gorman
2013-12-03 8:51 ` [PATCH 12/15] Clear numa on mprotect Mel Gorman
2013-12-03 8:51 ` Mel Gorman
2013-12-03 8:52 ` [PATCH 13/15] mm: numa: Avoid unnecessary disruption of NUMA hinting during migration Mel Gorman
2013-12-03 8:52 ` Mel Gorman
2013-12-03 8:52 ` [PATCH 14/15] mm: numa: Flush TLB if NUMA hinting faults race with PTE scan update Mel Gorman
2013-12-03 8:52 ` Mel Gorman
2013-12-03 23:07 ` Rik van Riel
2013-12-03 23:07 ` Rik van Riel
2013-12-03 23:46 ` Mel Gorman
2013-12-03 23:46 ` Mel Gorman
2013-12-04 14:33 ` Rik van Riel
2013-12-04 14:33 ` Rik van Riel
2013-12-04 16:07 ` Mel Gorman
2013-12-04 16:07 ` Mel Gorman
2013-12-05 15:40 ` Rik van Riel
2013-12-05 15:40 ` Rik van Riel
2013-12-05 19:54 ` Mel Gorman
2013-12-05 19:54 ` Mel Gorman
2013-12-05 20:05 ` Rik van Riel [this message]
2013-12-05 20:05 ` Rik van Riel
2013-12-06 9:24 ` Mel Gorman
2013-12-06 9:24 ` Mel Gorman
2013-12-06 17:38 ` Alex Thorlton
2013-12-06 17:38 ` Alex Thorlton
2013-12-06 18:32 ` Mel Gorman
2013-12-06 18:32 ` Mel Gorman
2013-12-06 19:13 ` [PATCH 14/15] mm: fix TLB flush race between migration, and change_protection_range Rik van Riel
2013-12-06 19:13 ` Rik van Riel
2013-12-06 20:32 ` Christoph Lameter
2013-12-06 20:32 ` Christoph Lameter
2013-12-06 21:21 ` Rik van Riel
2013-12-06 21:21 ` Rik van Riel
2013-12-07 0:25 ` Christoph Lameter
2013-12-07 0:25 ` Christoph Lameter
2013-12-07 3:14 ` Rik van Riel
2013-12-07 3:14 ` Rik van Riel
2013-12-09 16:00 ` Christoph Lameter
2013-12-09 16:00 ` Christoph Lameter
2013-12-09 16:27 ` Mel Gorman
2013-12-09 16:27 ` Mel Gorman
2013-12-09 16:59 ` Christoph Lameter
2013-12-09 16:59 ` Christoph Lameter
2013-12-09 21:01 ` Rik van Riel
2013-12-09 21:01 ` Rik van Riel
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