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=-5.3 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 6E1E3C47080 for ; Tue, 1 Jun 2021 12:45:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3DF70613C5 for ; Tue, 1 Jun 2021 12:45:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233835AbhFAMrS (ORCPT ); Tue, 1 Jun 2021 08:47:18 -0400 Received: from outbound-smtp55.blacknight.com ([46.22.136.239]:59057 "EHLO outbound-smtp55.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233657AbhFAMrR (ORCPT ); Tue, 1 Jun 2021 08:47:17 -0400 Received: from mail.blacknight.com (pemlinmail01.blacknight.ie [81.17.254.10]) by outbound-smtp55.blacknight.com (Postfix) with ESMTPS id D8825FB122 for ; Tue, 1 Jun 2021 13:45:34 +0100 (IST) Received: (qmail 716 invoked from network); 1 Jun 2021 12:45:34 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.17.255]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 1 Jun 2021 12:45:34 -0000 Date: Tue, 1 Jun 2021 13:45:33 +0100 From: Mel Gorman To: Jesper Dangaard Brouer Cc: Linux-MM , Dave Hansen , Vlastimil Babka , Michal Hocko , LKML , "netdev@vger.kernel.org" Subject: Re: [PATCH 2/2] mm/page_alloc: Allow high-order pages to be stored on the per-cpu lists Message-ID: <20210601124533.GU30378@techsingularity.net> References: <20210531120412.17411-1-mgorman@techsingularity.net> <20210531120412.17411-3-mgorman@techsingularity.net> <20210531172338.2e7cb070@carbon> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20210531172338.2e7cb070@carbon> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, May 31, 2021 at 05:23:38PM +0200, Jesper Dangaard Brouer wrote: > On Mon, 31 May 2021 13:04:12 +0100 > Mel Gorman wrote: > > > The per-cpu page allocator (PCP) only stores order-0 pages. This means > > that all THP and "cheap" high-order allocations including SLUB contends > > on the zone->lock. This patch extends the PCP allocator to store THP and > > "cheap" high-order pages. Note that struct per_cpu_pages increases in > > size to 256 bytes (4 cache lines) on x86-64. > > > > Note that this is not necessarily a universal performance win because of > > how it is implemented. High-order pages can cause pcp->high to be exceeded > > prematurely for lower-orders so for example, a large number of THP pages > > being freed could release order-0 pages from the PCP lists. Hence, much > > depends on the allocation/free pattern as observed by a single CPU to > > determine if caching helps or hurts a particular workload. > > > > That said, basic performance testing passed. The following is a netperf > > UDP_STREAM test which hits the relevant patches as some of the network > > allocations are high-order. > > This series[1] looks very interesting! I confirm that some network > allocations do use high-order allocations. Thus, I think this will > increase network performance in general, like you confirm below: > Would you be able to do a small test on a real high-speed network? It's something I can do easily myself in a few weeks but I do not have testbed readily available at the moment. It's ok if you do not have the time, it would just be nice if I could include independent results in the changelog if the results are positive. Alternatively, a negative result would mean going back to the drawing board :) -- Mel Gorman SUSE Labs