From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753067AbcLITkb (ORCPT ); Fri, 9 Dec 2016 14:40:31 -0500 Received: from outbound-smtp09.blacknight.com ([46.22.139.14]:50746 "EHLO outbound-smtp09.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752952AbcLITka (ORCPT ); Fri, 9 Dec 2016 14:40:30 -0500 Date: Fri, 9 Dec 2016 19:40:27 +0000 From: Mel Gorman To: Vlastimil Babka Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim , Michal Hocko , "Kirill A. Shutemov" , Johannes Weiner Subject: Re: [PATCH 1/2] mm, page_alloc: don't convert pfn to idx when merging Message-ID: <20161209194027.4ltdedctw2fshuwe@techsingularity.net> References: <20161209093754.3515-1-vbabka@suse.cz> <20161209172658.uebsgt5ju6gtz2bu@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.2 (2016-07-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 09, 2016 at 07:32:22PM +0100, Vlastimil Babka wrote: > > As a slight aside, I recently spotted that one of the largest overhead > > in the bulk free path was in the page_is_buddy() checks so pretty much > > anything that helps that is welcome. > > Interesting, the function shouldn't be doing really much on x86 without > debug config options? We might try further optimize the zone equivalence > checks, perhaps? I don't have the data any more but IIRC, it was cache miss intensive and I assumed at the time that it was checking cache cold struct pages during merges. At the time I was looking at splitting the per-cpu lists into irq and non-irq so wasn't focused on the page_is_buddy part of the profile. It just stuck in my mind as being surprisingly high. -- Mel Gorman SUSE Labs