From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f52.google.com (mail-pa0-f52.google.com [209.85.220.52]) by kanga.kvack.org (Postfix) with ESMTP id 4E3826B0255 for ; Wed, 2 Dec 2015 23:11:50 -0500 (EST) Received: by padhx2 with SMTP id hx2so59516759pad.1 for ; Wed, 02 Dec 2015 20:11:50 -0800 (PST) Received: from mail-pa0-x22a.google.com (mail-pa0-x22a.google.com. [2607:f8b0:400e:c03::22a]) by mx.google.com with ESMTPS id g73si9139519pfd.168.2015.12.02.20.11.49 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 02 Dec 2015 20:11:49 -0800 (PST) Received: by padhx2 with SMTP id hx2so59516607pad.1 for ; Wed, 02 Dec 2015 20:11:49 -0800 (PST) From: Joonsoo Kim Subject: [PATCH] mm/compaction: restore COMPACT_CLUSTER_MAX to 32 Date: Thu, 3 Dec 2015 13:11:40 +0900 Message-Id: <1449115900-20112-1-git-send-email-iamjoonsoo.kim@lge.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Vlastimil Babka , Mel Gorman , David Rientjes , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Joonsoo Kim Until now, COMPACT_CLUSTER_MAX is defined as SWAP_CLUSTER_MAX. Commit ("mm: increase SWAP_CLUSTER_MAX to batch TLB flushes") changes SWAP_CLUSTER_MAX from 32 to 256 to improve tlb flush performance so COMPACT_CLUSTER_MAX is also changed to 256. But, it has no justification on compaction-side and I think that loss is more than benefit. One example is that migration scanner would isolates and migrates too many pages unnecessarily with 256 COMPACT_CLUSTER_MAX. It may be enough to migrate 4 pages in order to make order-2 page, but, now, compaction will migrate 256 pages. To reduce this unneeded overhead, this patch restores COMPACT_CLUSTER_MAX to 32. Signed-off-by: Joonsoo Kim --- include/linux/swap.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index d08feef..31eb343 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -155,7 +155,7 @@ enum { }; #define SWAP_CLUSTER_MAX 256UL -#define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX +#define COMPACT_CLUSTER_MAX 32UL /* * Ratio between zone->managed_pages and the "gap" that above the per-zone -- 1.9.1 -- 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