Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756313Ab3IYXZ1 (ORCPT ); Wed, 25 Sep 2013 19:25:27 -0400 Received: from e28smtp09.in.ibm.com ([122.248.162.9]:58681 "EHLO e28smtp09.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755452Ab3IYXZY (ORCPT ); Wed, 25 Sep 2013 19:25:24 -0400 From: "Srivatsa S. Bhat" Subject: [RFC PATCH v4 33/40] mm: Use a cache between page-allocator and region-allocator To: akpm@linux-foundation.org, mgorman@suse.de, dave@sr71.net, hannes@cmpxchg.org, tony.luck@intel.com, matthew.garrett@nebula.com, riel@redhat.com, arjan@linux.intel.com, srinivas.pandruvada@linux.intel.com, willy@linux.intel.com, kamezawa.hiroyu@jp.fujitsu.com, lenb@kernel.org, rjw@sisk.pl Cc: gargankita@gmail.com, paulmck@linux.vnet.ibm.com, svaidy@linux.vnet.ibm.com, andi@firstfloor.org, isimatu.yasuaki@jp.fujitsu.com, santosh.shilimkar@ti.com, kosaki.motohiro@gmail.com, srivatsa.bhat@linux.vnet.ibm.com, linux-pm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Date: Thu, 26 Sep 2013 04:51:11 +0530 Message-ID: <20130925232109.26184.58513.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20130925231250.26184.31438.stgit@srivatsabhat.in.ibm.com> References: <20130925231250.26184.31438.stgit@srivatsabhat.in.ibm.com> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13092523-2674-0000-0000-00000ACC7FE3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2983 Lines: 73 Currently, whenever the page allocator notices that it has all the freepages of a given memory region, it attempts to return it back to the region allocator. This strategy is needlessly aggressive and can cause a lot of back and forth between the page-allocator and the region-allocator. More importantly, it can potentially completely wreck the benefits of having a region allocator in the first place - if the buddy allocator immediately returns freepages of memory regions to the region allocator, it goes back to the generic pool of pages. So, in future, depending on when the next allocation request arrives for this particular migratetype, the region allocator might not have any free regions to hand out, and hence we might end up falling back to freepages of other migratetypes. Instead, if the page allocator retains a few regions as a cache for every migratetype, we will have higher chances of avoiding fallbacks to other migratetypes. So, don't return all free memory regions (in the page allocator) to the region allocator. Keep atleast one region as a cache, for future use. Signed-off-by: Srivatsa S. Bhat --- mm/page_alloc.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index c4cbd80..a15ac96 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -640,9 +640,11 @@ static void add_to_region_allocator(struct zone *z, struct free_list *free_list, int region_id); -static inline int can_return_region(struct mem_region_list *region, int order) +static inline int can_return_region(struct mem_region_list *region, int order, + struct free_list *free_list) { struct zone_mem_region *zone_region; + struct page *prev_page, *next_page; zone_region = region->zone_region; @@ -660,6 +662,16 @@ static inline int can_return_region(struct mem_region_list *region, int order) if (likely(order != MAX_ORDER-1)) return 0; + /* + * Don't return all the regions; retain atleast one region as a + * cache for future use. + */ + prev_page = container_of(free_list->list.prev , struct page, lru); + next_page = container_of(free_list->list.next , struct page, lru); + + if (page_zone_region_id(prev_page) == page_zone_region_id(next_page)) + return 0; /* There is only one region in this freelist */ + if (region->nr_free * (1 << order) != zone_region->nr_free) return 0; @@ -729,7 +741,7 @@ try_return_region: * Try to return the freepages of a memory region to the region * allocator, if possible. */ - if (can_return_region(region, order)) + if (can_return_region(region, order, free_list)) add_to_region_allocator(page_zone(page), free_list, region_id); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/