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 18049C43143 for ; Mon, 1 Oct 2018 09:52:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CF88A2064A for ; Mon, 1 Oct 2018 09:52:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="aRvP6y2d" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CF88A2064A 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 S1729188AbeJAQ3q (ORCPT ); Mon, 1 Oct 2018 12:29:46 -0400 Received: from mail-yw1-f41.google.com ([209.85.161.41]:39433 "EHLO mail-yw1-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729045AbeJAQ3q (ORCPT ); Mon, 1 Oct 2018 12:29:46 -0400 Received: by mail-yw1-f41.google.com with SMTP id v1-v6so5207962ywv.6 for ; Mon, 01 Oct 2018 02:52:48 -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=Kcqd3Pcfb9xxD6yrIN5Zh0buM8KoteGB3Gfwl/+108g=; b=aRvP6y2dgw3/BG+E6XzF2ggDmSPXnM/Z+cAg8PGUuZfD7tsd3z/eHQ6XkAArIGUAAD 6d26o1XwuU39y324ABp3pRYR6++t6Qi5gSk6PVQfStPiMvNny41RtmomQp1m+BQte/hK /f5ollY5RBjwWhcU3MgwouWWzC6LzqxVfxfrqZRx5oySGAaTWtFJaw39iN+d0hIr0sBc BmXTUTJrUZDszDLoKAOFwrR+GAqdNASPR0kNJ9wa3Yj/8NgpIQFWqQI6W8AckrExvt5n 9BsIQ6pxa4eHVdP0sYZa3sSHJ0rnR8MCmSL75aWexjwcFHPv0aRvFJmYp1Vq0bQDoxKi 0SKA== 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=Kcqd3Pcfb9xxD6yrIN5Zh0buM8KoteGB3Gfwl/+108g=; b=mi3vRdAALPD2lSncFSvxSzngmup3M5edNohcH8onZt75NWmEa1OaE3JiczWMDK1KZL upue/CBcu092U4uhsUSVA64lA3xb+eJgUx12q4FkKdzbVVHWyL4LonE4VUMVIa2BjBg8 aGDMTZBfV2tpYBvkwH57tcDCRJDFXoiAr26SLERXXcpx17Jjti6+KFANPuMJhSKuA0fF PeHceSxkA0gB9Gu/St++nvaTGXg5XNE/NlII+aCPxqYZuXW7RGLr0+QTHxsm7xOKUPdp 7694ZP4g4XLkCjzc7qZ5VvBrKBhTEu17YZILUEc35g0EfbTr9VZTDoSFmdNvQOooiP/q AyQg== X-Gm-Message-State: ABuFfoiPmQ1oUZhQfv5mXVZKLpnHvAu40QBiQhhLAc/TJfFNkIiiDRGD 32eLtN8fKue0vruY4nI8L0wsY8hGgSkir3gKAzkNYbom X-Google-Smtp-Source: ACcGV60MmPKQ2gRlcMLwwKsiGkymY991QLpZIyI0RmFe0pjA6dUZSiqDLIyBqW7f9r/eGSid3dVo7kuJoVQBkgGKa+w= X-Received: by 2002:a81:2989:: with SMTP id p131-v6mr5200875ywp.176.1538387568168; Mon, 01 Oct 2018 02:52:48 -0700 (PDT) MIME-Version: 1.0 References: <20180930065100.GL15893@shao2-debian> <20181001093249.GD3913@quack2.suse.cz> In-Reply-To: <20181001093249.GD3913@quack2.suse.cz> From: Amir Goldstein Date: Mon, 1 Oct 2018 12:52:35 +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 12:32 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. > Indeed, I am still trying to figure out how to run lkp in my test env. Thanks, Amir.