From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751692Ab3LKSJ3 (ORCPT ); Wed, 11 Dec 2013 13:09:29 -0500 Received: from zene.cmpxchg.org ([85.214.230.12]:46164 "EHLO zene.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751561Ab3LKSJ0 (ORCPT ); Wed, 11 Dec 2013 13:09:26 -0500 From: Johannes Weiner To: Andrew Morton Cc: Dave Hansen , Mel Gorman , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [patch] mm: page_alloc: exclude unreclaimable allocations from zone fairness policy Date: Wed, 11 Dec 2013 13:09:16 -0500 Message-Id: <1386785356-19911-1-git-send-email-hannes@cmpxchg.org> X-Mailer: git-send-email 1.8.4.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dave Hansen noted a regression in a microbenchmark that loops around open() and close() on an 8-node NUMA machine and bisected it down to 81c0a2bb515f ("mm: page_alloc: fair zone allocator policy"). That change forces the slab allocations of the file descriptor to spread out to all 8 nodes, causing remote references in the page allocator and slab. The round-robin policy is only there to provide fairness among memory allocations that are reclaimed involuntarily based on pressure in each zone. It does not make sense to apply it to unreclaimable kernel allocations that are freed manually, in this case instantly after the allocation, and incur the remote reference costs twice for no reason. Only round-robin allocations that are usually freed through page reclaim or slab shrinking. Bisected-by: Dave Hansen Signed-off-by: Johannes Weiner Cc: --- mm/page_alloc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 580a5f075ed0..f861d0257e90 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1920,7 +1920,8 @@ zonelist_scan: * back to remote zones that do not partake in the * fairness round-robin cycle of this zonelist. */ - if (alloc_flags & ALLOC_WMARK_LOW) { + if ((alloc_flags & ALLOC_WMARK_LOW) && + (gfp_mask & GFP_MOVABLE_MASK)) { if (zone_page_state(zone, NR_ALLOC_BATCH) <= 0) continue; if (zone_reclaim_mode && -- 1.8.4.2