From: Nick Piggin 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 Signed-off-by: Andrew Morton --- mm/page_alloc.c | 12 ++++++++++++ 1 files changed, 12 insertions(+) diff -puN mm/page_alloc.c~mm-pcp-use-non-powers-of-2-for-batch-size mm/page_alloc.c --- 25/mm/page_alloc.c~mm-pcp-use-non-powers-of-2-for-batch-size 2005-04-26 05:06:18.546420992 -0700 +++ 25-akpm/mm/page_alloc.c 2005-04-26 05:06:18.554419776 -0700 @@ -1671,6 +1671,18 @@ static void __init free_area_init_core(s 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; _