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authorNick Piggin <nickpiggin@yahoo.com.au>2005-05-01 08:58:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-05-01 08:58:36 -0700
commit8e30f272a93ec9c1d5c305c5040dfaebc880499d (patch)
treeed5b54d2895d3e93768f79b2ec2b968f79bf7013 /mm
parent81b4082dc7666e2bc5ec229d8e837f3bafb96883 (diff)
[PATCH] mm: pcp use non powers of 2 for batch size
Jack Steiner reported this to have fixed his problem (bad colouring): "The patches fix both problems that I found - bad coloring & excessive pages in pagesets." In most workloads this is not likely to be such a pronounced problem, however it should help corner cases. And avoiding powers of 2 in these types of memory operations is always a good idea. Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/page_alloc.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c73dbbc1cd8f..08e8627361a0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1671,6 +1671,18 @@ static void __init free_area_init_core(struct pglist_data *pgdat,
if (batch < 1)
batch = 1;
+ /*
+ * Clamp the batch to a 2^n - 1 value. Having a power
+ * of 2 value was found to be more likely to have
+ * suboptimal cache aliasing properties in some cases.
+ *
+ * For example if 2 tasks are alternately allocating
+ * batches of pages, one task can end up with a lot
+ * of pages of one half of the possible page colors
+ * and the other with pages of the other colors.
+ */
+ batch = (1 << fls(batch + batch/2)) - 1;
+
for (cpu = 0; cpu < NR_CPUS; cpu++) {
struct per_cpu_pages *pcp;

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