[PATCH 7/12] Drain per-cpu lists when high-order allocations fail

[Mel Gorman]

Per-cpu pages can accidentally cause fragmentation because they are free, but
pinned pages in an otherwise contiguous block.  When this patch is applied,
the per-cpu caches are drained after the direct-reclaim is entered if the
requested order is greater than 0. It simply reuses the code used by suspend
and hotplug.

Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
---

 page_alloc.c |   28 +++++++++++++++++++++++++++-
 1 files changed, 27 insertions(+), 1 deletion(-)

diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.20-mm2-006_configurable/mm/page_alloc.c linux-2.6.20-mm2-007_drainpercpu/mm/page_alloc.c
--- linux-2.6.20-mm2-006_configurable/mm/page_alloc.c	2007-02-20 18:33:41.000000000 +0000
+++ linux-2.6.20-mm2-007_drainpercpu/mm/page_alloc.c	2007-02-20 18:35:52.000000000 +0000
@@ -916,7 +916,9 @@ void mark_free_pages(struct zone *zone)
 
 	spin_unlock_irqrestore(&zone->lock, flags);
 }
+#endif /* CONFIG_PM */
 
+#if defined(CONFIG_PM) || defined(CONFIG_PAGE_GROUP_BY_MOBILITY)
 /*
  * Spill all of this CPU's per-cpu pages back into the buddy allocator.
  */
@@ -928,7 +930,28 @@ void drain_local_pages(void)
 	__drain_pages(smp_processor_id());
 	local_irq_restore(flags);	
 }
-#endif /* CONFIG_PM */
+
+void smp_drain_local_pages(void *arg)
+{
+	drain_local_pages();
+}
+
+/*
+ * Spill all the per-cpu pages from all CPUs back into the buddy allocator
+ */
+void drain_all_local_pages(void)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	__drain_pages(smp_processor_id());
+	local_irq_restore(flags);
+
+	smp_call_function(smp_drain_local_pages, NULL, 0, 1);
+}
+#else
+void drain_all_local_pages(void) {}
+#endif /* CONFIG_PM || CONFIG_PAGE_GROUP_BY_MOBILITY */
 
 /*
  * Free a 0-order page
@@ -1557,6 +1580,9 @@ nofail_alloc:
 
 	cond_resched();
 
+	if (order != 0)
+		drain_all_local_pages();
+
 	if (likely(did_some_progress)) {
 		page = get_page_from_freelist(gfp_mask, order,
 						zonelist, alloc_flags);
-
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