From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5CFABC433E0 for ; Thu, 28 Jan 2021 14:44:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1EF0764DE9 for ; Thu, 28 Jan 2021 14:44:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231128AbhA1OoB (ORCPT ); Thu, 28 Jan 2021 09:44:01 -0500 Received: from outbound-smtp22.blacknight.com ([81.17.249.190]:53599 "EHLO outbound-smtp22.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231550AbhA1Onl (ORCPT ); Thu, 28 Jan 2021 09:43:41 -0500 Received: from mail.blacknight.com (pemlinmail06.blacknight.ie [81.17.255.152]) by outbound-smtp22.blacknight.com (Postfix) with ESMTPS id 3ACA6BAE48 for ; Thu, 28 Jan 2021 14:42:47 +0000 (GMT) Received: (qmail 20546 invoked from network); 28 Jan 2021 14:42:46 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.22.4]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 28 Jan 2021 14:42:46 -0000 Date: Thu, 28 Jan 2021 14:42:45 +0000 From: Mel Gorman To: Michal Hocko Cc: Vincent Guittot , Vlastimil Babka , Christoph Lameter , Bharata B Rao , linux-kernel , linux-mm@kvack.org, David Rientjes , Joonsoo Kim , Andrew Morton , guro@fb.com, Shakeel Butt , Johannes Weiner , aneesh.kumar@linux.ibm.com, Jann Horn Subject: Re: [RFC PATCH v0] mm/slub: Let number of online CPUs determine the slub page order Message-ID: <20210128144245.GH3592@techsingularity.net> References: <20201118082759.1413056-1-bharata@linux.ibm.com> <20210121053003.GB2587010@in.ibm.com> <20210126085243.GE827@dhcp22.suse.cz> <20210126135918.GQ827@dhcp22.suse.cz> <20210128134512.GF3592@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 28, 2021 at 02:57:10PM +0100, Michal Hocko wrote: > On Thu 28-01-21 13:45:12, Mel Gorman wrote: > [...] > > So mostly this is down to the number of times SLUB calls into the page > > allocator which only caches order-0 pages on a per-cpu basis. I do have > > a prototype for a high-order per-cpu allocator but it is very rough -- > > high watermarks stop making sense, code is rough, memory needed for the > > pcpu structures quadruples etc. > > Thanks this is really useful. But it really begs a question whether this > is a general case or more an exception. And as such maybe we want to > define high throughput caches which would gain a higher order pages to > keep pace with allocation and reduce the churn or deploy some other > techniques to reduce the direct page allocator involvement. I don't think we want to define "high throughput caches" because it'll be workload dependant and a game of whack-a-mole. If the "high throughput cache" is a kmalloc cache for some set of workloads and one of the inode caches or dcaches for another one, there will be no setting that is universally good. -- Mel Gorman SUSE Labs