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=-2.2 required=3.0 tests=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 CE9F6C43603 for ; Wed, 11 Dec 2019 15:54:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AE3E120836 for ; Wed, 11 Dec 2019 15:54:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732936AbfLKPyG (ORCPT ); Wed, 11 Dec 2019 10:54:06 -0500 Received: from mail.monom.org ([188.138.9.77]:55848 "EHLO mail.monom.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730284AbfLKPyF (ORCPT ); Wed, 11 Dec 2019 10:54:05 -0500 Received: from mail.monom.org (localhost [127.0.0.1]) by filter.mynetwork.local (Postfix) with ESMTP id EB052500796; Wed, 11 Dec 2019 16:54:02 +0100 (CET) Received: from [192.168.154.174] (b9168f78.cgn.dg-w.de [185.22.143.120]) by mail.monom.org (Postfix) with ESMTPSA id 76B80500243; Wed, 11 Dec 2019 16:54:02 +0100 (CET) Subject: Re: Patch "mm, vmstat: make quiet_vmstat lighter" has been added to the 4.4-stable tree To: Greg KH , "zhangyi (F)" Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, cl@linux.com, mgalbraith@suse.de, mhocko@suse.com, torvalds@linux-foundation.org, umgwanakikbuti@gmail.com, stable-commits@vger.kernel.org, "Wangkefeng (Maro)" , Xie XiuQi References: <156442332854185@kroah.com> <20191211144614.GA637714@kroah.com> From: Daniel Wagner Message-ID: <40460b0c-7fb0-a19d-3684-cb020e226a3f@monom.org> Date: Wed, 11 Dec 2019 16:54:01 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <20191211144614.GA637714@kroah.com> Content-Type: text/plain; charset=utf-8; format=flowed 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 Hi, On 2019-12-11 15:46, Greg KH wrote: > On Wed, Dec 11, 2019 at 10:32:49PM +0800, zhangyi (F) wrote: >> We find a performance degradation under lmbench af_unix[1] test case after >> mergeing this patch on my x86 qemu 4.4 machine. The test result is basically >> stable for each teses. >> >> Host machine: CPU: Intel(R) Xeon(R) CPU E5-2690 v3 >> CPU(s): 48 >> MEM: 193047 MB >> >> Guest machine: CPU: QEMU Virtual CPU version 2.5+ >> CPU(s): 8 >> MEM: 26065 MB >> >> Before this patch: >> [root@localhost ~]# lmbench-3.0-a9/bin/x86_64-linux-gnu/lat_unix -P 1 >> AF_UNIX sock stream latency: 133.7073 microseconds >> >> After this patch: >> [root@localhost ~]# lmbench-3.0-a9/bin/x86_64-linux-gnu/lat_unix -P 1 >> AF_UNIX sock stream latency: 156.4722 microseconds >> >> If we set task to a constant cpu, the degradation does not appear. >> >> Before this patch: >> [root@localhost ~]# lmbench-3.0-a9/bin/x86_64-linux-gnu/lat_unix -P 1 >> AF_UNIX sock stream latency: 17.9296 microseconds >> >> After this patch: >> [root@localhost ~]# lmbench-3.0-a9/bin/x86_64-linux-gnu/lat_unix -P 1 >> AF_UNIX sock stream latency: 17.7500 microseconds >> >> We also test it on the aarch64 hi1215 machine with 8 cpu cores. >> >> Before this patch: >> [root@localhost ~]# ./lat_unix -P 1 >> AF_UNIX sock stream latency: 30.7 microseconds >> >> After this patch: >> [root@localhost ~]# ./lat_unix -P 1 >> AF_UNIX sock stream latency: 37.5 microseconds >> >> Accessories included my reproduce config for x86 qemu. Any thoughts? > > This fixes a bug, as reported by Daniel Wagner. So it's probably better > to have a stable system instead of a broken one, right? :) > > Daniel can provide more information if needed. IIRC, this patch got necessary because bdf3c006b9a2 ("vmstat: make vmstat_updater deferrable again and shut down on idle") was added to stable. Without it v4.4-rt is not working at all. > What about when you run your tests on a 4.9 or newer kernel that > already has this integrated? That said, I was going through all changes in vmstat.c upstream and we backported almost all changes to v4.4 at that point. So if this is a really giving you a performance hit, I suspect you would see it upstream as well. Thanks, Daniel