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=-5.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 B034CC4338F for ; Tue, 24 Aug 2021 16:22:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9159F6127B for ; Tue, 24 Aug 2021 16:22:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231764AbhHXQXa (ORCPT ); Tue, 24 Aug 2021 12:23:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48220 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229712AbhHXQX3 (ORCPT ); Tue, 24 Aug 2021 12:23:29 -0400 Received: from mail-lj1-x231.google.com (mail-lj1-x231.google.com [IPv6:2a00:1450:4864:20::231]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 15156C061757 for ; Tue, 24 Aug 2021 09:22:45 -0700 (PDT) Received: by mail-lj1-x231.google.com with SMTP id j12so24208340ljg.10 for ; Tue, 24 Aug 2021 09:22:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=1p0o+1bDBZZcnsbLlc+PmnEMPXHkkQy0tdXGmQ6Xogw=; b=TcgS1rL1D8BQMVtkdScnlO21S3L66Y9bLv0UsZgVlbeY8aWmtB8Bc3KZihbGnZssfP fuyPam7MRSa8eyXR/2iWv+bt/frKdz5+YfNixZAdFT1iXCYI5PqqmfptmUY+GzG5/GR1 BRkT3/V9mj9I+AsCCITn8bJ2cwS2EH4imPghs= 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=1p0o+1bDBZZcnsbLlc+PmnEMPXHkkQy0tdXGmQ6Xogw=; b=ByAP0aHmKsw1fKTzVtSIazlLTNL9H/CmhrgKTZiStrLBuNFw9tVrAdR2qprT62k8Kd f7SoANwzRforthIGHdtm1qvp5cnmXNiE77ZeemKyeok8BJVcvWs1qsGrgnZ92xJbXlyi ZYYPWvChIP6lLHe3ytTE2YfDOZ16o8nXsLrqKM1qt4ZdaFt0kcwq+qjsyATGyC4l+WoZ AWPtxuvvCIt+dNjKBVmdfbTFmag7/wDeodT68+FeQmYPnVYXPXmi7h9lsefZs9Z9F1aq sh6dcHeOgIOOVJVLN5j8scqRVRP5113lfJWPggvZYf2GaDnCZ1EC9lzy6XDsC9ySwQbT 7ilw== X-Gm-Message-State: AOAM5302TPOSu+9nbE99iXhMyq8X6y3SgFwFG52v0122JOYNiMtHGKYf 8Yp1HvVJ2sNmS1tfErMPhfoSwrLsFI7MrNyB X-Google-Smtp-Source: ABdhPJzUimBD8v19jhcVovP4Udq/uxc6xqz2LNCMO675XJcTUIaUlfHbG42As1zUbAaVOjF+5s/nlw== X-Received: by 2002:a2e:8001:: with SMTP id j1mr11322051ljg.9.1629822163094; Tue, 24 Aug 2021 09:22:43 -0700 (PDT) Received: from mail-lf1-f44.google.com (mail-lf1-f44.google.com. [209.85.167.44]) by smtp.gmail.com with ESMTPSA id r11sm1840381ljk.71.2021.08.24.09.22.41 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 24 Aug 2021 09:22:41 -0700 (PDT) Received: by mail-lf1-f44.google.com with SMTP id i9so46679587lfg.10 for ; Tue, 24 Aug 2021 09:22:41 -0700 (PDT) X-Received: by 2002:a19:500e:: with SMTP id e14mr28511435lfb.487.1629822161302; Tue, 24 Aug 2021 09:22:41 -0700 (PDT) MIME-Version: 1.0 References: <20210824151337.GC27667@xsang-OptiPlex-9020> In-Reply-To: <20210824151337.GC27667@xsang-OptiPlex-9020> From: Linus Torvalds Date: Tue, 24 Aug 2021 09:22:25 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [pipe] 3b844826b6: stress-ng.sigio.ops_per_sec -99.3% regression To: kernel test robot Cc: Sandeep Patil , Mel Gorman , LKML , lkp@lists.01.org, kernel test robot , "Huang, Ying" , Feng Tang , Zhengjun Xing Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 24, 2021 at 7:56 AM kernel test robot wrote: > > FYI, we noticed a -99.3% regression of stress-ng.sigio.ops_per_sec due to commit: Well, that's bad. > commit: 3b844826b6c6 ("pipe: avoid unnecessary EPOLLET wakeups under normal loads") You fix one benchmark, you break another.. What's a bit odd is that this commit basically reverts commit 3a34b13a88ca ("pipe: make pipe writes always wake up readers") which did *not* result in any kernel test robot report. It's not a pure revert, because it adds that 'poll_usage' case (for EPOLLET), but the stress-ng.sigio test doesn't even use select or poll (ok, there's a select() call with an empty file descriptor set, which seems to be just an odd way to spell "usleep()"). So it _looks_ to me like it's a 100% revert in practice for that test. I strace'd the "stress-ng --sigio" case just to make sure I didn't miss anything. But I'm clearly missing something. Can anybody see what I'm missing, and hit me over the head with the clue-bat? Linus