From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932561AbcLGP5y (ORCPT ); Wed, 7 Dec 2016 10:57:54 -0500 Received: from outbound-smtp09.blacknight.com ([46.22.139.14]:37651 "EHLO outbound-smtp09.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932359AbcLGP5x (ORCPT ); Wed, 7 Dec 2016 10:57:53 -0500 Date: Wed, 7 Dec 2016 15:57:50 +0000 From: Mel Gorman To: Christoph Lameter Cc: Andrew Morton , Michal Hocko , Vlastimil Babka , Johannes Weiner , Jesper Dangaard Brouer , Joonsoo Kim , Linux-MM , Linux-Kernel Subject: Re: [PATCH] mm: page_alloc: High-order per-cpu page allocator v7 Message-ID: <20161207155750.yfsizliaoodks5k4@techsingularity.net> References: <20161207101228.8128-1-mgorman@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 Wed, Dec 07, 2016 at 08:52:27AM -0600, Christoph Lameter wrote: > On Wed, 7 Dec 2016, Mel Gorman wrote: > > > SLUB has been the default small kernel object allocator for quite some time > > but it is not universally used due to performance concerns and a reliance > > on high-order pages. The high-order concerns has two major components -- > > SLUB does not rely on high order pages. It falls back to lower order if > the higher orders are not available. Its a performance concern. > Ok -- While SLUB does not rely on high-order pages for functional correctness, it perfoms better if high-order pages are available. > This is also an issue for various other kernel subsystems that really > would like to have larger contiguous memory area. We are often seeing > performance constraints due to the high number of 4k segments when doing > large scale block I/O f.e. > Which is related to the fundamentals of fragmentation control in general. At some point there will have to be a revisit to get back to the type of reliability that existed in 3.0-era without the massive overhead it incurred. As stated before, I agree it's important but outside the scope of this patch. -- Mel Gorman SUSE Labs