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

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@csn.ul.ie>
---

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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