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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04A17C433FE for ; Tue, 2 Nov 2021 07:58:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D5D1C61051 for ; Tue, 2 Nov 2021 07:58:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230411AbhKBIA5 (ORCPT ); Tue, 2 Nov 2021 04:00:57 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]:53092 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229577AbhKBIAz (ORCPT ); Tue, 2 Nov 2021 04:00:55 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 7CF2B21956; Tue, 2 Nov 2021 07:58:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1635839900; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=2Q5NQ8/JaSAadnmMaZCcDJCUm9UQGbRtMuNPV5QIcjg=; b=L4qSVqPdh2DwLCV3D9HiXPxpJbPkp9C52tQvxiTnn2cTWzlzOGs76zHugFR6XWOihhlaBe VeEdpbo6wnfgbgCdivb0WiXi50X3JYGa/bwFSGoK2HByPUjrMy5a+FyVCETcnyRia53KR6 tXiGVTD93/L46fOvvLI9jEktDyU371s= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 1B66BA3B8B; Tue, 2 Nov 2021 07:58:19 +0000 (UTC) Date: Tue, 2 Nov 2021 08:58:19 +0100 From: Michal Hocko To: Suren Baghdasaryan Cc: Andrew Morton , David Rientjes , Matthew Wilcox , Johannes Weiner , Roman Gushchin , Rik van Riel , Minchan Kim , Christian Brauner , Christoph Hellwig , Oleg Nesterov , David Hildenbrand , Jann Horn , Shakeel Butt , Andy Lutomirski , Christian Brauner , Florian Weimer , Jan Engelhardt , Linux API , linux-mm , LKML , kernel-team , "Kirill A. Shutemov" , Andrea Arcangeli Subject: Re: [PATCH 1/1] mm: prevent a race between process_mrelease and exit_mmap Message-ID: References: <20211022014658.263508-1-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 01-11-21 08:44:58, Suren Baghdasaryan wrote: [...] > I'm with you on this one, that's why I wanted to measure the price we > would pay. Below are the test results: > > Test: https://lore.kernel.org/all/20170725142626.GJ26723@dhcp22.suse.cz/ > Compiled: gcc -O2 -static test.c -o test > Test machine: 128 core / 256 thread 2x AMD EPYC 7B12 64-Core Processor > (family 17h) > > baseline (Linus master, f31531e55495ca3746fb895ffdf73586be8259fa) > p50 (median) 87412 > p95 168210 > p99 190058 > average 97843.8 > stdev 29.85% > > unconditional mmap_write_lock in exit_mmap (last column is the change > from the baseline) > p50 (median) 88312 +1.03% > p95 170797 +1.54% > p99 191813 +0.92% > average 97659.5 -0.19% > stdev 32.41% > > unconditional mmap_write_lock in exit_mmap + Matthew's patch (last > column is the change from the baseline) > p50 (median) 88807 +1.60% > p95 167783 -0.25% > p99 187853 -1.16% > average 97491.4 -0.36% > stdev 30.61% > > stdev is quite high in all cases, so the test is very noisy. > The impact seems quite low IMHO. WDYT? Results being very noisy is what I recall as well. Thanks! -- Michal Hocko SUSE Labs