linux-kernel - [PATCH v3 5/5] mm: Only IPI CPUs to drain local pages if they exist

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Date:	Sun, 13 Nov 2011 12:17:29 +0200
From:	Gilad Ben-Yossef <gilad@...yossef.com>
To:	linux-kernel@...r.kernel.org
Cc:	Gilad Ben-Yossef <gilad@...yossef.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Russell King <linux@....linux.org.uk>, linux-mm@...ck.org,
	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>,
	Sasha Levin <levinsasha928@...il.com>,
	Rik van Riel <riel@...hat.com>,
	Andi Kleen <andi@...stfloor.org>
Subject: [PATCH v3 5/5] mm: Only IPI CPUs to drain local pages if they exist

Calculate a cpumask of CPUs with per-cpu pages in any zone
and only send an IPI requesting CPUs to drain these pages
to the buddy allocator if they actually have pages when
asked to flush.

The code path of memory allocation failure for CPUMASK_OFFSTACK=y
config was tested using fault injection framework.

Signed-off-by: Gilad Ben-Yossef <gilad@...yossef.com>
Acked-by: Chris Metcalf <cmetcalf@...era.com>
CC: Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC: Frederic Weisbecker <fweisbec@...il.com>
CC: Russell King <linux@....linux.org.uk>
CC: linux-mm@...ck.org
CC: Christoph Lameter <cl@...ux-foundation.org>
CC: Pekka Enberg <penberg@...nel.org>
CC: Matt Mackall <mpm@...enic.com>
CC: Sasha Levin <levinsasha928@...il.com>
CC: Rik van Riel <riel@...hat.com>
CC: Andi Kleen <andi@...stfloor.org>
---
 mm/page_alloc.c |   18 +++++++++++++++++-
 1 files changed, 17 insertions(+), 1 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9dd443d..44dc6c5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1119,7 +1119,23 @@ void drain_local_pages(void *arg)
  */
 void drain_all_pages(void)
 {
-	on_each_cpu(drain_local_pages, NULL, 1);
+	int cpu;
+	struct zone *zone;
+	cpumask_var_t cpus;
+	struct per_cpu_pageset *pageset;
+
+	if (likely(zalloc_cpumask_var(&cpus, GFP_ATOMIC))) {
+		for_each_populated_zone(zone) {
+			for_each_online_cpu(cpu) {
+				pageset = per_cpu_ptr(zone->pageset, cpu);
+				if (pageset->pcp.count)
+					cpumask_set_cpu(cpu, cpus);
+		}
+	}
+		on_each_cpu_mask(cpus, drain_local_pages, NULL, 1);
+		free_cpumask_var(cpus);
+	} else
+		on_each_cpu(drain_local_pages, NULL, 1);
 }
 
 #ifdef CONFIG_HIBERNATION
-- 
1.7.0.4

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