Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965534AbaKLBsp (ORCPT ); Tue, 11 Nov 2014 20:48:45 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:60844 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965471AbaKLBsk (ORCPT ); Tue, 11 Nov 2014 20:48:40 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vlastimil Babka , Leon Romanovsky , Johannes Weiner , Mel Gorman , Andrew Morton , Linus Torvalds Subject: [PATCH 3.14 203/203] mm: page_alloc: fix zone allocation fairness on UP Date: Wed, 12 Nov 2014 10:17:53 +0900 Message-Id: <20141112011552.007597313@linuxfoundation.org> X-Mailer: git-send-email 2.1.3 In-Reply-To: <20141112011542.686743533@linuxfoundation.org> References: <20141112011542.686743533@linuxfoundation.org> User-Agent: quilt/0.63-1 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.14-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. Commit 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 Cc: [3.12+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/page_alloc.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1957,7 +1957,7 @@ 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; } /* @@ -5670,9 +5670,8 @@ 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); -- 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/