From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753869AbaEFRZY (ORCPT ); Tue, 6 May 2014 13:25:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:2154 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752638AbaEFRZW (ORCPT ); Tue, 6 May 2014 13:25:22 -0400 Message-ID: <53691AF9.7080608@redhat.com> Date: Tue, 06 May 2014 13:25:13 -0400 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Mel Gorman , Linux-MM , Linux-FSDevel CC: Johannes Weiner , Vlastimil Babka , Jan Kara , Michal Hocko , Hugh Dickins , Linux Kernel Subject: Re: [PATCH 07/17] mm: page_alloc: Take the ALLOC_NO_WATERMARK check out of the fast path References: <1398933888-4940-1-git-send-email-mgorman@suse.de> <1398933888-4940-8-git-send-email-mgorman@suse.de> In-Reply-To: <1398933888-4940-8-git-send-email-mgorman@suse.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/01/2014 04:44 AM, Mel Gorman wrote: > ALLOC_NO_WATERMARK is set in a few cases. Always by kswapd, always for > __GFP_MEMALLOC, sometimes for swap-over-nfs, tasks etc. Each of these cases > are relatively rare events but the ALLOC_NO_WATERMARK check is an unlikely > branch in the fast path. This patch moves the check out of the fast path > and after it has been determined that the watermarks have not been met. This > helps the common fast path at the cost of making the slow path slower and > hitting kswapd with a performance cost. It's a reasonable tradeoff. > > Signed-off-by: Mel Gorman > Acked-by: Johannes Weiner Reviewed-by: Rik van Riel -- All rights reversed