From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id 765F2828E1 for ; Fri, 24 Jun 2016 06:01:23 -0400 (EDT) Received: by mail-wm0-f72.google.com with SMTP id f126so13207598wma.3 for ; Fri, 24 Jun 2016 03:01:23 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id i194si3226192wme.39.2016.06.24.02.55.04 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 24 Jun 2016 02:55:04 -0700 (PDT) From: Vlastimil Babka Subject: [PATCH v3 16/17] mm, compaction: require only min watermarks for non-costly orders Date: Fri, 24 Jun 2016 11:54:36 +0200 Message-Id: <20160624095437.16385-17-vbabka@suse.cz> In-Reply-To: <20160624095437.16385-1-vbabka@suse.cz> References: <20160624095437.16385-1-vbabka@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Mel Gorman , Joonsoo Kim , David Rientjes , Rik van Riel , Vlastimil Babka The __compaction_suitable() function checks the low watermark plus a compact_gap() gap to decide if there's enough free memory to perform compaction. Then __isolate_free_page uses low watermark check to decide if particular free page can be isolated. In the latter case, using low watermark is needlessly pessimistic, as the free page isolations are only temporary. For __compaction_suitable() the higher watermark makes sense for high-order allocations where more freepages increase the chance of success, and we can typically fail with some order-0 fallback when the system is struggling to reach that watermark. But for low-order allocation, forming the page should not be that hard. So using low watermark here might just prevent compaction from even trying, and eventually lead to OOM killer even if we are above min watermarks. So after this patch, we use min watermark for non-costly orders in __compaction_suitable(), and for all orders in __isolate_free_page(). Signed-off-by: Vlastimil Babka Acked-by: Michal Hocko --- mm/compaction.c | 6 +++++- mm/page_alloc.c | 2 +- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 3b774befb62a..ddff4cc48067 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1403,10 +1403,14 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order, * isolation. We however do use the direct compactor's classzone_idx to * skip over zones where lowmem reserves would prevent allocation even * if compaction succeeds. + * For costly orders, we require low watermark instead of min for + * compaction to proceed to increase its chances. * ALLOC_CMA is used, as pages in CMA pageblocks are considered * suitable migration targets */ - watermark = low_wmark_pages(zone) + compact_gap(order); + watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ? + low_wmark_pages(zone) : min_wmark_pages(zone); + watermark += compact_gap(order); if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx, ALLOC_CMA, wmark_target)) return COMPACT_SKIPPED; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 9510b91517dd..4a963659f8bb 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2502,7 +2502,7 @@ int __isolate_free_page(struct page *page, unsigned int order) if (!is_migrate_isolate(mt)) { /* Obey watermarks as if the page was being allocated */ - watermark = low_wmark_pages(zone) + (1 << order); + watermark = min_wmark_pages(zone) + (1UL << order); if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA)) return 0; -- 2.8.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org