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| author | Nick Piggin <nickpiggin@yahoo.com.au> | 2005-05-01 08:58:36 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-05-01 08:58:36 -0700 |
| commit | 8e30f272a93ec9c1d5c305c5040dfaebc880499d (patch) | |
| tree | ed5b54d2895d3e93768f79b2ec2b968f79bf7013 /mm/page_alloc.c | |
| parent | 81b4082dc7666e2bc5ec229d8e837f3bafb96883 (diff) | |
| download | lwn-8e30f272a93ec9c1d5c305c5040dfaebc880499d.tar.gz lwn-8e30f272a93ec9c1d5c305c5040dfaebc880499d.zip | |
[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/page_alloc.c')
| -rw-r--r-- | mm/page_alloc.c | 12 |
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; |