From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f70.google.com (mail-wm0-f70.google.com [74.125.82.70]) by kanga.kvack.org (Postfix) with ESMTP id CFEF0680FC1 for ; Tue, 14 Feb 2017 11:35:05 -0500 (EST) Received: by mail-wm0-f70.google.com with SMTP id c85so8860200wmi.6 for ; Tue, 14 Feb 2017 08:35:05 -0800 (PST) Received: from gum.cmpxchg.org (gum.cmpxchg.org. [85.214.110.215]) by mx.google.com with ESMTPS id k4si1766850wmf.93.2017.02.14.08.35.04 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 14 Feb 2017 08:35:04 -0800 (PST) Date: Tue, 14 Feb 2017 11:34:53 -0500 From: Johannes Weiner Subject: Re: [PATCH v2 02/10] mm, compaction: remove redundant watermark check in compact_finished() Message-ID: <20170214163453.GC2450@cmpxchg.org> References: <20170210172343.30283-1-vbabka@suse.cz> <20170210172343.30283-3-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170210172343.30283-3-vbabka@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: linux-mm@kvack.org, Joonsoo Kim , David Rientjes , Mel Gorman , linux-kernel@vger.kernel.org, kernel-team@fb.com On Fri, Feb 10, 2017 at 06:23:35PM +0100, Vlastimil Babka wrote: > When detecting whether compaction has succeeded in forming a high-order page, > __compact_finished() employs a watermark check, followed by an own search for > a suitable page in the freelists. This is not ideal for two reasons: > > - The watermark check also searches high-order freelists, but has a less strict > criteria wrt fallback. It's therefore redundant and waste of cycles. This was > different in the past when high-order watermark check attempted to apply > reserves to high-order pages. > > - The watermark check might actually fail due to lack of order-0 pages. > Compaction can't help with that, so there's no point in continuing because of > that. It's possible that high-order page still exists and it terminates. > > This patch therefore removes the watermark check. This should save some cycles > and terminate compaction sooner in some cases. > > Signed-off-by: Vlastimil Babka Acked-by: Johannes Weiner -- 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