Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758190AbaJIVRb (ORCPT ); Thu, 9 Oct 2014 17:17:31 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:59682 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757939AbaJIVLx (ORCPT ); Thu, 9 Oct 2014 17:11:53 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Johannes Weiner , Andrew Morton , Kamal Mostafa Subject: [PATCH 3.13 159/163] mm: page_alloc: fix zone allocation fairness on UP Date: Thu, 9 Oct 2014 14:03:04 -0700 Message-Id: <1412888588-26755-160-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1412888588-26755-1-git-send-email-kamal@canonical.com> References: <1412888588-26755-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.13.11.9 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Johannes Weiner commit abe5f972912d086c080be4bde67750630b6fb38b upstream. The zone allocation batches can easily underflow due to higher-order allocations or spills to remote nodes. On SMP that's fine, because underflows are expected from concurrency and dealt with by returning 0. But on UP, zone_page_state will just return a wrapped unsigned long, which will get past the <= 0 check and then consider the zone eligible until its watermarks are hit. 3a025760fc15 ("mm: page_alloc: spill to remote nodes before waking kswapd") already made the counter-resetting use atomic_long_read() to accomodate underflows from remote spills, but it didn't go all the way with it. Make it clear that these batches are expected to go negative regardless of concurrency, and use atomic_long_read() everywhere. Fixes: 81c0a2bb515f ("mm: page_alloc: fair zone allocator policy") Reported-by: Vlastimil Babka Reported-by: Leon Romanovsky Signed-off-by: Johannes Weiner Acked-by: Mel Gorman Signed-off-by: Andrew Morton [ kamal: Johannes' 3.12 backport applied to 3.13-stable ] Signed-off-by: Kamal Mostafa --- mm/page_alloc.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 9aad4f1..38dca81 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1932,7 +1932,7 @@ zonelist_scan: if (alloc_flags & ALLOC_FAIR) { if (!zone_local(preferred_zone, zone)) continue; - if (zone_page_state(zone, NR_ALLOC_BATCH) <= 0) + if (atomic_long_read(&zone->vm_stat[NR_ALLOC_BATCH]) <= 0) continue; } /* @@ -5599,9 +5599,8 @@ static void __setup_per_zone_wmarks(void) zone->watermark[WMARK_HIGH] = min_wmark_pages(zone) + (tmp >> 1); __mod_zone_page_state(zone, NR_ALLOC_BATCH, - high_wmark_pages(zone) - - low_wmark_pages(zone) - - zone_page_state(zone, NR_ALLOC_BATCH)); + high_wmark_pages(zone) - low_wmark_pages(zone) - + atomic_long_read(&zone->vm_stat[NR_ALLOC_BATCH])); setup_zone_migrate_reserve(zone); spin_unlock_irqrestore(&zone->lock, flags); -- 1.9.1 -- 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/