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=-6.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS autolearn=ham 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 6272AC10F27 for ; Mon, 9 Mar 2020 14:36:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 354DB21655 for ; Mon, 9 Mar 2020 14:36:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583764596; bh=SagHTacFC7nUvUy/V0aicAWyNUl19D+O0X84xGBwYR4=; h=Subject:From:To:Cc:Date:In-Reply-To:References:List-ID:From; b=js/0iGvSusCyMv5XvmpZMdeceHxn4430qtdUcpAuiI7R93q6c9ns9Fxkexoq/9qP0 AJryOl+3OCCV/lHVwpsdAGk+WLViSNn6IanO4s0Zems7uDH6OMmdzItFbuQShtvv8H 3GMswxbtObt+YqAIb1WFpUXZBS1aB9RR81uhWx80= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726814AbgCIOgf (ORCPT ); Mon, 9 Mar 2020 10:36:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:37794 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726400AbgCIOge (ORCPT ); Mon, 9 Mar 2020 10:36:34 -0400 Received: from tleilax.poochiereds.net (68-20-15-154.lightspeed.rlghnc.sbcglobal.net [68.20.15.154]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A2B912067C; Mon, 9 Mar 2020 14:36:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583764594; bh=SagHTacFC7nUvUy/V0aicAWyNUl19D+O0X84xGBwYR4=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=z4OU62tiqctI6JpAwROtj9AshzZtgak8fRMdxDLU71NHK7Trb7flfIV+UrcOzua0i l26ifi10dO5vo+vtIROBhhLtKpDcFnaxPFpDBGwVcIQn0D1IffTmzIXwvnSrNU8Rb0 +TUIMu+p2wPrTatTi7ckYWAsL86o8pASee4a7oGw= Message-ID: Subject: Re: [locks] 6d390e4b5d: will-it-scale.per_process_ops -96.6% regression From: Jeff Layton To: kernel test robot , yangerkun Cc: LKML , Linus Torvalds , lkp@lists.01.org, Neil Brown , Bruce Fields , Al Viro Date: Mon, 09 Mar 2020 10:36:32 -0400 In-Reply-To: <20200308140314.GQ5972@shao2-debian> References: <20200308140314.GQ5972@shao2-debian> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.34.4 (3.34.4-1.fc31) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2020-03-08 at 22:03 +0800, kernel test robot wrote: > Greeting, > > FYI, we noticed a -96.6% regression of will-it-scale.per_process_ops due to commit: > > > commit: 6d390e4b5d48ec03bb87e63cf0a2bff5f4e116da ("locks: fix a potential use-after-free problem when wakeup a waiter") > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master > > in testcase: will-it-scale > on test machine: 288 threads Intel(R) Xeon Phi(TM) CPU 7295 @ 1.50GHz with 80G memory > with following parameters: > > nr_task: 100% > mode: process > test: lock1 > cpufreq_governor: performance > ucode: 0x11 > > test-description: Will It Scale takes a testcase and runs it from 1 through to n parallel copies to see if the testcase will scale. It builds both a process and threads based test in order to see any differences between the two. > test-url: https://github.com/antonblanchard/will-it-scale > > In addition to that, the commit also has significant impact on the following tests: > > +------------------+----------------------------------------------------------------------+ > > testcase: change | will-it-scale: will-it-scale.per_thread_ops -51.3% regression | > > test machine | 288 threads Intel(R) Xeon Phi(TM) CPU 7295 @ 1.50GHz with 80G memory | > > test parameters | cpufreq_governor=performance | > > | mode=thread | > > | nr_task=100% | > > | test=lock1 | > > | ucode=0x11 | > +------------------+----------------------------------------------------------------------+ > This is not completely unexpected as we're banging on the global blocked_lock_lock now for every unlock. This test just thrashes file locks and unlocks without doing anything in between, so the workload looks pretty artificial [1]. It would be nice to avoid the global lock in this codepath, but it doesn't look simple to do. I'll keep thinking about it, but for now I'm inclined to ignore this result unless we see a problem in more realistic workloads. [1]: https://github.com/antonblanchard/will-it-scale/blob/master/tests/lock1.c -- Jeff Layton