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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 EC94BCA9EB0 for ; Mon, 21 Oct 2019 11:42:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C179D214AE for ; Mon, 21 Oct 2019 11:42:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728482AbfJULma (ORCPT ); Mon, 21 Oct 2019 07:42:30 -0400 Received: from mx2.suse.de ([195.135.220.15]:35854 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727962AbfJULma (ORCPT ); Mon, 21 Oct 2019 07:42:30 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id E4829B7CE; Mon, 21 Oct 2019 11:42:26 +0000 (UTC) Subject: Re: [PATCH 1/3] mm, meminit: Recalculate pcpu batch and high limits after init completes To: Mel Gorman , Andrew Morton Cc: Michal Hocko , Thomas Gleixner , Matt Fleming , Borislav Petkov , Linux-MM , Linux Kernel Mailing List References: <20191021094808.28824-1-mgorman@techsingularity.net> <20191021094808.28824-2-mgorman@techsingularity.net> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; prefer-encrypt=mutual; keydata= mQINBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy 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5ZFJyfGsOiNUcMoO/17FO4EBxSDP3FDLllpuzlFD7SXkfJaMWYmXIlO0jLzdfwfcnDzBbPwO hBM8hvtsyq8lq8vJOxv6XD6xcTtj5Az8t2JjdUX6SF9hxJpwhBU0wrCoGDkWp4Bbv6jnF7zP Nzftr4l8RuJoywDIiJpdaNpSlXKpj/K6KrnyAI/joYc7 Message-ID: Date: Mon, 21 Oct 2019 13:42:25 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20191021094808.28824-2-mgorman@techsingularity.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/21/19 11:48 AM, Mel Gorman wrote: > Deferred memory initialisation updates zone->managed_pages during > the initialisation phase but before that finishes, the per-cpu page > allocator (pcpu) calculates the number of pages allocated/freed in > batches as well as the maximum number of pages allowed on a per-cpu list. > As zone->managed_pages is not up to date yet, the pcpu initialisation > calculates inappropriately low batch and high values. > > This increases zone lock contention quite severely in some cases with the > degree of severity depending on how many CPUs share a local zone and the > size of the zone. A private report indicated that kernel build times were > excessive with extremely high system CPU usage. A perf profile indicated > that a large chunk of time was lost on zone->lock contention. > > This patch recalculates the pcpu batch and high values after deferred > initialisation completes for every populated zone in the system. It > was tested on a 2-socket AMD EPYC 2 machine using a kernel compilation > workload -- allmodconfig and all available CPUs. > > mmtests configuration: config-workload-kernbench-max > Configuration was modified to build on a fresh XFS partition. > > kernbench > 5.4.0-rc3 5.4.0-rc3 > vanilla resetpcpu-v2 > Amean user-256 13249.50 ( 0.00%) 16401.31 * -23.79%* > Amean syst-256 14760.30 ( 0.00%) 4448.39 * 69.86%* > Amean elsp-256 162.42 ( 0.00%) 119.13 * 26.65%* > Stddev user-256 42.97 ( 0.00%) 19.15 ( 55.43%) > Stddev syst-256 336.87 ( 0.00%) 6.71 ( 98.01%) > Stddev elsp-256 2.46 ( 0.00%) 0.39 ( 84.03%) > > 5.4.0-rc3 5.4.0-rc3 > vanilla resetpcpu-v2 > Duration User 39766.24 49221.79 > Duration System 44298.10 13361.67 > Duration Elapsed 519.11 388.87 > > The patch reduces system CPU usage by 69.86% and total build time by > 26.65%. The variance of system CPU usage is also much reduced. > > Before, this was the breakdown of batch and high values over all zones was. > > 256 batch: 1 > 256 batch: 63 > 512 batch: 7 > 256 high: 0 > 256 high: 378 > 512 high: 42 > > 512 pcpu pagesets had a batch limit of 7 and a high limit of 42. After the patch > > 256 batch: 1 > 768 batch: 63 > 256 high: 0 > 768 high: 378 > > Cc: stable@vger.kernel.org # v4.1+ > Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka > --- > mm/page_alloc.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index c0b2e0306720..f972076d0f6b 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1947,6 +1947,14 @@ void __init page_alloc_init_late(void) > /* Block until all are initialised */ > wait_for_completion(&pgdat_init_all_done_comp); > > + /* > + * The number of managed pages has changed due to the initialisation > + * so the pcpu batch and high limits needs to be updated or the limits > + * will be artificially small. > + */ > + for_each_populated_zone(zone) > + zone_pcp_update(zone); > + > /* > * We initialized the rest of the deferred pages. Permanently disable > * on-demand struct page initialization. >