From ba56e91c940146e99ac694c4c7cd7f2b4aaa565d Mon Sep 17 00:00:00 2001 From: "Seth, Rohit" <rohit.seth@intel.com> Date: Sat, 29 Oct 2005 18:15:47 -0700 Subject: [PATCH] [PATCH] mm: page_alloc: increase size of per-cpu-pages Increase the page allocator's per-cpu magazines from 1/4MB to 1/2MB. Over 100+ runs for a workload, the difference in mean is about 2%. The best results for both are almost same. Though the max variation in results with 1/2MB is only 2.2%, whereas with 1/4MB it is 12%. Signed-off-by: Rohit Seth <rohit.seth@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org> --- mm/page_alloc.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 94c864eac9c48..f799217dc2f3e 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1721,29 +1721,29 @@ static int __devinit zone_batchsize(struct zone *zone) /* * The per-cpu-pages pools are set to around 1000th of the - * size of the zone. But no more than 1/4 of a meg - there's - * no point in going beyond the size of L2 cache. + * size of the zone. But no more than 1/2 of a meg. * * OK, so we don't know how big the cache is. So guess. */ batch = zone->present_pages / 1024; - if (batch * PAGE_SIZE > 256 * 1024) - batch = (256 * 1024) / PAGE_SIZE; + if (batch * PAGE_SIZE > 512 * 1024) + batch = (512 * 1024) / PAGE_SIZE; batch /= 4; /* We effectively *= 4 below */ 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. + * We will be trying to allcoate bigger chunks of contiguous + * memory of the order of fls(batch). This should result in + * better cache coloring. * - * 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. + * A sanity check also to ensure that batch is still in limits. */ - batch = (1 << fls(batch + batch/2)) - 1; + batch = (1 << fls(batch + batch/2)); + + if (fls(batch) >= (PAGE_SHIFT + MAX_ORDER - 2)) + batch = PAGE_SHIFT + ((MAX_ORDER - 1 - PAGE_SHIFT)/2); + return batch; } -- 2.30.2