From: Nick Piggin Date: Sun, 4 Dec 2005 02:55:25 +0000 (+1100) Subject: [PATCH] Fix up per-cpu page batch sizes X-Git-Tag: v2.6.15-rc5~3 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0ceaacc9785fedc500e19b024d606a82a23f5372;p=linux-2.6 [PATCH] Fix up per-cpu page batch sizes The code to clamp batch sizes to 2^n - 1 went missing and an extra check got added, which must have been a hunk of the "higer order pcp batch refills" work sneaking in. Signed-off-by: Nick Piggin Signed-off-by: Linus Torvalds --- diff --git a/mm/page_alloc.c b/mm/page_alloc.c index b257720edf..3b21a13d84 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1772,16 +1772,16 @@ static int __devinit zone_batchsize(struct zone *zone) batch = 1; /* - * We will be trying to allcoate bigger chunks of contiguous - * memory of the order of fls(batch). This should result in - * better cache coloring. + * 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. * - * A sanity check also to ensure that batch is still in limits. + * 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)); - - if (fls(batch) >= (PAGE_SHIFT + MAX_ORDER - 2)) - batch = PAGE_SHIFT + ((MAX_ORDER - 1 - PAGE_SHIFT)/2); + batch = (1 << (fls(batch + batch/2)-1)) - 1; return batch; }