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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 80A90C43143 for ; Tue, 2 Oct 2018 14:49:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 47B502082A for ; Tue, 2 Oct 2018 14:49:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="jnMARkSm" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 47B502082A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728643AbeJBVd0 (ORCPT ); Tue, 2 Oct 2018 17:33:26 -0400 Received: from mail-yw1-f68.google.com ([209.85.161.68]:35675 "EHLO mail-yw1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726552AbeJBVdZ (ORCPT ); Tue, 2 Oct 2018 17:33:25 -0400 Received: by mail-yw1-f68.google.com with SMTP id y76-v6so853058ywd.2 for ; Tue, 02 Oct 2018 07:49:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=HWvAH8hkjtkAuohQgK1B9p5lEx209J/nEFP5Wps4HGo=; b=jnMARkSmW5Jq8DtqgwtNs5Vfz5jOzrmnd7gCSmlioGy1xv73VBO1N+7ytQqhFWviu3 /0s5mpq7gehr2OasARhKNO8IMJr9Sk4GqXkQ6gahCJyWX/vKW1C8ixGInci3xC/WFDsJ ZY6th2soLsYl7ERTGxLHb/gJ2vWapAFywaIIuUSEn2C67kCyR2A8DGrPZgYk41By6CFQ 9Ezr3ZL17tibVJB6EzQ/yDzVdOGtSAtgrUSZVdJEg/IhHuGpY/rGgIVA7bdy0dGTXJjx fkEuxv7MDWZeGy9aak/zfHkp4h7U3rJMeXn3Kz4GG9Ps6OpCqZe+tV76BW2kdQTIKure CqHg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=HWvAH8hkjtkAuohQgK1B9p5lEx209J/nEFP5Wps4HGo=; b=ShHcghc8jd47XPe5c0s23t+GdvFkUMrucDE+BnBSe4K4PJxrr5nhI8pWLcdWfXt3z7 a2Z2ikLIGoxaVZS/2xLHOkCQDNYFSyNlH6EtR3ONR6GnGzX8xK2tu3cbFfr4vt9fzhYc H6/pgZQ3bq9rDBgHXO9IFj0nMWjsx6EIKURcO1kHbhVZWUMTU9gseDieYzHTZsD1+AYW PMwPOZ6W8DJqyvK0yRoj+WQkIAGu7llA0DJ3lOdIyO4w2J1mkQI6FbDBdrQcgTbsQdrZ DU5JQjgHdeWkWaFZSQQ0pt3MDZPdMKciAK919PfcJxAX9pKNtWwkUlfjoL4UaYSOc36m 9DFw== X-Gm-Message-State: ABuFfojl8gHLaEavaaczVuK6DYapNIKJ9LaC7wPWFKBukfSxQ4TYz41v Dww5kuAo0hHEaB6kNhSHqyD3pUaOrJa6yaqpKPJj3w== X-Google-Smtp-Source: ACcGV63Yw8UTvJLuEotPz+Qr2fa0qCapkWNDtzfoQGMU4BzcVWyS75kjC9AwwdtllP5WEctmho2LeexbGeRiMtlSLgc= X-Received: by 2002:a81:ae4e:: with SMTP id g14-v6mr8566571ywk.248.1538491778910; Tue, 02 Oct 2018 07:49:38 -0700 (PDT) MIME-Version: 1.0 References: <20180930065100.GL15893@shao2-debian> <20181001093249.GD3913@quack2.suse.cz> In-Reply-To: From: Amir Goldstein Date: Tue, 2 Oct 2018 17:49:27 +0300 Message-ID: Subject: Re: [LKP] [fsnotify] 60f7ed8c7c: will-it-scale.per_thread_ops -5.9% regression To: Jan Kara Cc: rong.a.chen@intel.com, linux-kernel , Stephen Rothwell , LKP Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 1, 2018 at 12:52 PM Amir Goldstein wrote: > > On Mon, Oct 1, 2018 at 12:32 PM Jan Kara wrote: > > > > On Sun 30-09-18 12:00:46, Amir Goldstein wrote: > [...] > > > > commit: > > > > 1e6cb72399 ("fsnotify: add super block object type") > > > > 60f7ed8c7c ("fsnotify: send path type events to group with super block marks") > > > > > > > > > > I have to admit this looks strange. > > > All this commit does is dereference mnt->mnt.mnt_sb and then > > > sb->s_fsnotify_mask/sb->s_fsnotify_marks to find that they are zero. > > > AFAICT there should be no extra contention added by this commit and it's > > > hard to believe that parallel unlink workload would suffer from this change. > > > > Well, it could be those additional fetches of > > sb->s_fsnotify_mask/sb->s_fsnotify_marks if they happen to be cache cold. > > Or it could be just code layout differences (i.e., compiler is not able to > > optimize resulting code as good or the code layout just happens to align > > with cache lines in a wrong way or something like that). Anyway, without > > being able to reproduce this and do detailed comparison of perf profiles I > > don't think we'll be able to tell. > > > On my test machine, I couldn't measure a difference in results between the two commits, but it may be because my test machine is not strong enough to drive the test. It only has 4 cores and so I could only reach ~1/4 of the workload reported by 0day robot. I tested both 16-thread and 4-thread jobs. In both cases the measured difference between the two commits was less than 0.5% and within the stddev margins. I will see if I can get my hands on a stronger test machine. Thanks, Amir.