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From: Mel Gorman <mgorman@suse.de>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Ingo Molnar <mingo@kernel.org>
Cc: Rik van Riel <riel@redhat.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Hugh Dickins <hughd@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Paul Turner <pjt@google.com>, Hillf Danton <dhillf@gmail.com>,
	David Rientjes <rientjes@google.com>,
	Lee Schermerhorn <Lee.Schermerhorn@hp.com>,
	Alex Shi <lkml.alex@gmail.com>,
	Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
	Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux-MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>, Mel Gorman <mgorman@suse.de>
Subject: [PATCH 07/49] mm: Optimize the TLB flush of sys_mprotect() and change_protection() users
Date: Fri,  7 Dec 2012 10:23:10 +0000	[thread overview]
Message-ID: <1354875832-9700-8-git-send-email-mgorman@suse.de> (raw)
In-Reply-To: <1354875832-9700-1-git-send-email-mgorman@suse.de>

From: Ingo Molnar <mingo@kernel.org>

Reuse the NUMA code's 'modified page protections' count that
change_protection() computes and skip the TLB flush if there's
no changes to a range that sys_mprotect() modifies.

Given that mprotect() already optimizes the same-flags case
I expected this optimization to dominantly trigger on
CONFIG_NUMA_BALANCING=y kernels - but even with that feature
disabled it triggers rather often.

There's two reasons for that:

1)

While sys_mprotect() already optimizes the same-flag case:

        if (newflags == oldflags) {
                *pprev = vma;
                return 0;
        }

and this test works in many cases, but it is too sharp in some
others, where it differentiates between protection values that the
underlying PTE format makes no distinction about, such as
PROT_EXEC == PROT_READ on x86.

2)

Even where the pte format over vma flag changes necessiates a
modification of the pagetables, there might be no pagetables
yet to modify: they might not be instantiated yet.

During a regular desktop bootup this optimization hits a couple
of hundred times. During a Java test I measured thousands of
hits.

So this optimization improves sys_mprotect() in general, not just
CONFIG_NUMA_BALANCING=y kernels.

[ We could further increase the efficiency of this optimization if
  change_pte_range() and change_huge_pmd() was a bit smarter about
  recognizing exact-same-value protection masks - when the hardware
  can do that safely. This would probably further speed up mprotect(). ]

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 mm/mprotect.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 1e265be..7c3628a 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -153,7 +153,9 @@ static unsigned long change_protection_range(struct vm_area_struct *vma,
 				 dirty_accountable);
 	} while (pgd++, addr = next, addr != end);
 
-	flush_tlb_range(vma, start, end);
+	/* Only flush the TLB if we actually modified any entries: */
+	if (pages)
+		flush_tlb_range(vma, start, end);
 
 	return pages;
 }
-- 
1.7.9.2

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  parent reply	other threads:[~2012-12-07 10:24 UTC|newest]

Thread overview: 84+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-12-07 10:23 [PATCH 00/49] Automatic NUMA Balancing v10 Mel Gorman
2012-12-07 10:23 ` [PATCH 01/49] x86: mm: only do a local tlb flush in ptep_set_access_flags() Mel Gorman
2012-12-07 10:23 ` [PATCH 02/49] x86: mm: drop TLB flush from ptep_set_access_flags Mel Gorman
2012-12-07 10:23 ` [PATCH 03/49] mm,generic: only flush the local TLB in ptep_set_access_flags Mel Gorman
2012-12-07 10:23 ` [PATCH 04/49] x86/mm: Introduce pte_accessible() Mel Gorman
2012-12-07 10:23 ` [PATCH 05/49] mm: Only flush the TLB when clearing an accessible pte Mel Gorman
2012-12-07 10:23 ` [PATCH 06/49] mm: Count the number of pages affected in change_protection() Mel Gorman
2012-12-07 10:23 ` Mel Gorman [this message]
2012-12-07 10:23 ` [PATCH 08/49] mm: compaction: Move migration fail/success stats to migrate.c Mel Gorman
2012-12-07 10:23 ` [PATCH 09/49] mm: migrate: Add a tracepoint for migrate_pages Mel Gorman
2012-12-07 10:23 ` [PATCH 10/49] mm: compaction: Add scanned and isolated counters for compaction Mel Gorman
2012-12-07 10:23 ` [PATCH 11/49] mm: numa: define _PAGE_NUMA Mel Gorman
2012-12-07 10:23 ` [PATCH 12/49] mm: numa: pte_numa() and pmd_numa() Mel Gorman
2012-12-07 10:23 ` [PATCH 13/49] mm: numa: Support NUMA hinting page faults from gup/gup_fast Mel Gorman
2012-12-07 10:23 ` [PATCH 14/49] mm: numa: split_huge_page: transfer the NUMA type from the pmd to the pte Mel Gorman
2012-12-07 10:23 ` [PATCH 15/49] mm: numa: Create basic numa page hinting infrastructure Mel Gorman
2012-12-07 10:23 ` [PATCH 16/49] mm: mempolicy: Make MPOL_LOCAL a real policy Mel Gorman
2012-12-07 10:23 ` [PATCH 17/49] mm: mempolicy: Add MPOL_NOOP Mel Gorman
2012-12-07 10:23 ` [PATCH 18/49] mm: mempolicy: Check for misplaced page Mel Gorman
2012-12-07 10:23 ` [PATCH 19/49] mm: migrate: Introduce migrate_misplaced_page() Mel Gorman
2012-12-07 10:23 ` [PATCH 20/49] mm: migrate: Drop the misplaced pages reference count if the target node is full Mel Gorman
2012-12-07 10:23 ` [PATCH 21/49] mm: mempolicy: Use _PAGE_NUMA to migrate pages Mel Gorman
2012-12-07 10:23 ` [PATCH 22/49] mm: mempolicy: Add MPOL_MF_LAZY Mel Gorman
2013-01-05  5:18   ` Simon Jeons
2013-01-07 15:14     ` Mel Gorman
2012-12-07 10:23 ` [PATCH 23/49] mm: mempolicy: Implement change_prot_numa() in terms of change_protection() Mel Gorman
2012-12-07 10:23 ` [PATCH 24/49] mm: mempolicy: Hide MPOL_NOOP and MPOL_MF_LAZY from userspace for now Mel Gorman
2012-12-07 10:23 ` [PATCH 25/49] mm: numa: Add fault driven placement and migration Mel Gorman
2013-01-04 11:56   ` Simon Jeons
2012-12-07 10:23 ` [PATCH 26/49] mm: sched: numa: Implement constant, per task Working Set Sampling (WSS) rate Mel Gorman
2012-12-07 10:23 ` [PATCH 27/49] sched, numa, mm: Count WS scanning against present PTEs, not virtual memory ranges Mel Gorman
2012-12-07 10:23 ` [PATCH 28/49] mm: sched: numa: Implement slow start for working set sampling Mel Gorman
2012-12-07 10:23 ` [PATCH 29/49] mm: numa: Add pte updates, hinting and migration stats Mel Gorman
2013-01-04 11:42   ` Simon Jeons
2013-01-07 15:29     ` Mel Gorman
2013-01-08  1:21       ` Wanpeng Li
2013-01-08  1:21       ` Wanpeng Li
2012-12-07 10:23 ` [PATCH 30/49] mm: numa: Migrate on reference policy Mel Gorman
2012-12-07 10:23 ` [PATCH 31/49] mm: numa: Migrate pages handled during a pmd_numa hinting fault Mel Gorman
2012-12-07 10:23 ` [PATCH 32/49] mm: numa: Structures for Migrate On Fault per NUMA migration rate limiting Mel Gorman
2012-12-07 10:23 ` [PATCH 33/49] mm: numa: Rate limit the amount of memory that is migrated between nodes Mel Gorman
2012-12-07 10:23 ` [PATCH 34/49] mm: numa: Rate limit setting of pte_numa if node is saturated Mel Gorman
2012-12-07 10:23 ` [PATCH 35/49] sched: numa: Slowly increase the scanning period as NUMA faults are handled Mel Gorman
2012-12-07 10:23 ` [PATCH 36/49] mm: numa: Introduce last_nid to the page frame Mel Gorman
2012-12-07 10:23 ` [PATCH 37/49] mm: numa: split_huge_page: Transfer last_nid on tail page Mel Gorman
2012-12-07 10:23 ` [PATCH 38/49] mm: numa: migrate: Set last_nid on newly allocated page Mel Gorman
2012-12-07 10:23 ` [PATCH 39/49] mm: numa: Use a two-stage filter to restrict pages being migrated for unlikely task<->node relationships Mel Gorman
2012-12-07 10:23 ` [PATCH 40/49] mm: sched: Adapt the scanning rate if a NUMA hinting fault does not migrate Mel Gorman
2012-12-07 10:23 ` [PATCH 41/49] mm: sched: numa: Control enabling and disabling of NUMA balancing Mel Gorman
2012-12-07 10:23 ` [PATCH 42/49] mm: sched: numa: Control enabling and disabling of NUMA balancing if !SCHED_DEBUG Mel Gorman
2012-12-07 10:23 ` [PATCH 43/49] mm: sched: numa: Delay PTE scanning until a task is scheduled on a new node Mel Gorman
2012-12-07 10:23 ` [PATCH 44/49] mm: numa: Add THP migration for the NUMA working set scanning fault case Mel Gorman
2013-01-05  8:42   ` Wanpeng Li
2013-01-05  8:42   ` Wanpeng Li
2013-01-07 15:37     ` Mel Gorman
2012-12-07 10:23 ` [PATCH 45/49] mm: numa: Add THP migration for the NUMA working set scanning fault case build fix Mel Gorman
2012-12-07 10:23 ` [PATCH 46/49] mm: numa: Account for failed allocations and isolations as migration failures Mel Gorman
2012-12-07 10:23 ` [PATCH 47/49] mm: migrate: Account a transhuge page properly when rate limiting Mel Gorman
2012-12-07 10:23 ` [PATCH 48/49] mm/rmap: Convert the struct anon_vma::mutex to an rwsem Mel Gorman
2012-12-07 10:23 ` [PATCH 49/49] mm/rmap, migration: Make rmap_walk_anon() and try_to_unmap_anon() more scalable Mel Gorman
2012-12-07 11:01 ` [PATCH 00/49] Automatic NUMA Balancing v10 Ingo Molnar
2012-12-09 20:36   ` Mel Gorman
2012-12-09 21:17     ` Kirill A. Shutemov
2012-12-10  8:44       ` Mel Gorman
2012-12-10  5:07     ` Srikar Dronamraju
2012-12-10  6:28       ` Srikar Dronamraju
2012-12-10 12:44         ` [PATCH] sched: Fix task_numa_fault() + KSM crash Ingo Molnar
2012-12-13 13:57           ` Srikar Dronamraju
2012-12-10  8:46       ` [PATCH 00/49] Automatic NUMA Balancing v10 Mel Gorman
2012-12-10 12:35       ` Ingo Molnar
2012-12-10 11:39     ` Ingo Molnar
2012-12-10 11:53       ` Ingo Molnar
2012-12-10 15:24       ` Mel Gorman
2012-12-11  1:02         ` Mel Gorman
2012-12-11  8:52           ` Ingo Molnar
2012-12-11  9:18             ` Ingo Molnar
2012-12-11 15:22               ` Mel Gorman
2012-12-11 16:30             ` Mel Gorman
2012-12-17 10:33               ` Ingo Molnar
2012-12-10 16:42 ` Srikar Dronamraju
2012-12-10 19:23   ` Ingo Molnar
2012-12-10 23:35     ` Srikar Dronamraju
2012-12-10 23:40   ` Srikar Dronamraju
2012-12-13 13:21 ` Srikar Dronamraju

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