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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 519D6C43603 for ; Sun, 8 Dec 2019 18:05:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 07A48205ED for ; Sun, 8 Dec 2019 18:05:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1575828326; bh=r4FhTC/6xvh6w6pD7bept1+KbN5XHcZPNqJ9cWc1TA8=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=EDCt+4+0e6pNNmXrY7+mXIoQkI344uOw357ubGNNb/rNQKT/ysQBXqtK26gjfLR9w S7QqJyt6gtow1djSYm2Br+G/ARiwRpQmJf4/L5nSkNcoheEVN9Rl+3TwrA4FgEJkyP RIFuYnBqeA7xFGkUNy1GrRoL7zkZ7N09ztuRN080= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726553AbfLHSFM (ORCPT ); Sun, 8 Dec 2019 13:05:12 -0500 Received: from mail-lf1-f66.google.com ([209.85.167.66]:36719 "EHLO mail-lf1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726474AbfLHSFL (ORCPT ); Sun, 8 Dec 2019 13:05:11 -0500 Received: by mail-lf1-f66.google.com with SMTP id n12so8936674lfe.3 for ; Sun, 08 Dec 2019 10:05:10 -0800 (PST) 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=ABGlqVpN991a0nTMf6FEfD82UigkTYB16rwzNeGUA1o=; b=fNvOByc3NZ0GAbRWTSkpquabTeoYcVtplUCgZggq3Aepi3EzJPLXx3abo3pWsDs5qf sKNddR4IqoNSKmAJDSPx/RmG6lgfadYTYSOho6JTjI6xasLvp6XbhfV12IZg7Fxv9hB/ sv5caupH6WixLG01Msc9x2ZAIOHmQ87OQdy5A= 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=ABGlqVpN991a0nTMf6FEfD82UigkTYB16rwzNeGUA1o=; b=s/hU5Pga91Ki1IWa2qDZjBxV2nn4cDcEGYqrNRz2nouswr8RmBRXxvq52k7DVXvBmC 6TxQmm2hM3+c6QN0b31RQqmbT4FY0UItiiEC6LD5GwPsakrHrNa2gnZQ+bR2bbPkwMlw 1y3vk0m9VN0oBSAHotZsEJHPmGhidHS2OVodQLfVkOs/wgdUtFhaK6lzzQDAeuCNSU/S 5kBlKDPz1anQlXqQ+wKS8Zx8FQT/7uJRMpmzFH3XehDT4dkkp2AZ9xlej3gYNZqARRzR Th07A507vBwRaIKITYjiLhQX1Lp9noRqe9oaunjP2/UAo4O5fHUTpuBL9itYtHAjn07s CFMg== X-Gm-Message-State: APjAAAUmN0JDZiqUVyuUTJl/IHsMFjtj8HTVkHdIyczDoZC/EhPZEJpP 5ZcfkPgkgYbdis35co8LsqB1vaG74pA= X-Google-Smtp-Source: APXvYqx+fM1KtF14GamFD1u5wHme+fUnT5MVClWlXsGipD7Wn8Sy9XITlzljTFywDADyMbnvcxEpbg== X-Received: by 2002:a19:7d04:: with SMTP id y4mr8830478lfc.111.1575828309322; Sun, 08 Dec 2019 10:05:09 -0800 (PST) Received: from mail-lj1-f174.google.com (mail-lj1-f174.google.com. [209.85.208.174]) by smtp.gmail.com with ESMTPSA id j10sm1451667ljc.76.2019.12.08.10.05.08 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 08 Dec 2019 10:05:08 -0800 (PST) Received: by mail-lj1-f174.google.com with SMTP id h23so13017770ljc.8 for ; Sun, 08 Dec 2019 10:05:08 -0800 (PST) X-Received: by 2002:a05:651c:239:: with SMTP id z25mr12153795ljn.48.1575828307903; Sun, 08 Dec 2019 10:05:07 -0800 (PST) MIME-Version: 1.0 References: <157558502272.10278.8718685637610645781.stgit@warthog.procyon.org.uk> <20191206135604.GB2734@twin.jikos.cz> In-Reply-To: From: Linus Torvalds Date: Sun, 8 Dec 2019 10:04:51 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 0/2] pipe: Fixes [ver #2] To: Akemi Yagi Cc: Linux Kernel Mailing List , David Howells 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 Sun, Dec 8, 2019 at 8:46 AM Akemi Yagi wrote: > > I forgot to mention that the aforementioned bug in make was originally > reported for Fedora. They now have a patched version of make > (make-4.2.1-15.fc32) in Rawhide. Yes, as mentioned I do expect it's some jobserver interaction - I've seen bad jobserver behavior before. But my 'make' hasn't been upgraded since May, as far as I can tell from my logs, so the huge performance regression was new. So the huge slowdown is real, and was triggered by the kernel changes. But yes, it's entirely possible - even likely - that it's due to a jobserver bug that ends up being sensitive to scheduling. We do treat even "user space is buggy and shouldn't have done that" as a regression. It's annoying. Timing-related issues are some of the worst to debug. Particularly when (at least I) primarily debug by looking at the code and trying to see what's wrong that way. Linus