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=-2.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 CA8CAC432C3 for ; Sat, 16 Nov 2019 16:57:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8AE9F2168B for ; Sat, 16 Nov 2019 16:57:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="N0rkrwOS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727996AbfKPQ5L (ORCPT ); Sat, 16 Nov 2019 11:57:11 -0500 Received: from mail-pf1-f182.google.com ([209.85.210.182]:46598 "EHLO mail-pf1-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727629AbfKPQ5L (ORCPT ); Sat, 16 Nov 2019 11:57:11 -0500 Received: by mail-pf1-f182.google.com with SMTP id 193so8143311pfc.13 for ; Sat, 16 Nov 2019 08:57:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=wCeZ0NDBlm1EZsjaPHiNTtKC7YyU9Uu+b4m8bOtAPXg=; b=N0rkrwOS9sB1urDsg27aLJxdVbBic6I77fwClS0ekU7+kMm4LFytBJ6m455Cg+hMfE 9aoLbJ/CWtbq36rAKzdmNsB811neVbr6WZdIS/SCe/Vw2SNw9a2tbzfAZQ5QCeoYA6Ny p4K1bmFpnYHEq2qOoaZdfuKPMJfl131COdOkrhLL/GGhUsra7BRgRf4GVFDYKvEHbhpY dlbUQ+PlzSGh23WFx78F2vU/sQ7+lWJw9agZH25VqeMOk1FZwLvRrqxq1IPtqsvYLJnh w28rGzcw2Elq+2fbU2h+HJ9ms6A/Pog88PpTOz1U0zv+Oj+YaNWJv4DU3Bbxn4ICdrKT ib/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=wCeZ0NDBlm1EZsjaPHiNTtKC7YyU9Uu+b4m8bOtAPXg=; b=EiGAb1lzNTtz1Z0UED9R0nniEJIxScCPdKy/HqEfOX96djCPtogi4/+0GEzRN8QlZO PxE+POiHlGNHur05+26ca+QdnIXJK8KCTWHq06+vXMSfXVgwGAYZS0RLnkVD9+onc/p6 TFCS5c6iJYPFWwpd3ZDe3zQNsSBKhbjopXrdzxGqXgrPDKBYj1H4ps6kESN3cdZDT81f ngnwt4XN8Rdd7pGQqrdmHNulCG51JlPZsPamErt5ZFivCd4khz72+lsTjyhS43+KQ7Q5 4EEBNsz08awYKyLDS0+7jb2Ic5CDCgQrEZe3T829sSnpyxT8tb4ZPqQFIrNEXTlMA0Eb UIeg== X-Gm-Message-State: APjAAAW9b7lCkFI/HyvA/noZuLXRb0BqgzU8/r3rI+ZGMxxXBlaSQLSD MBlpFTOuVU5geEdh6uSGeFFc7lDcSik= X-Google-Smtp-Source: APXvYqy28OXnOcl3MnoKQYULSLufjgDhybJA8Jumo7y7yI158d4acIWCAag6l/sfkVj2Li7NJ/MQHg== X-Received: by 2002:a62:c1c1:: with SMTP id i184mr24285676pfg.65.1573923429814; Sat, 16 Nov 2019 08:57:09 -0800 (PST) Received: from [192.168.1.188] ([66.219.217.79]) by smtp.gmail.com with ESMTPSA id fz12sm12738027pjb.15.2019.11.16.08.57.07 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 16 Nov 2019 08:57:08 -0800 (PST) Subject: Re: Recent slowdown in single object builds To: Masahiro Yamada Cc: "linux-kernel@vger.kernel.org" References: From: Jens Axboe Message-ID: <8caa1edf-9c6f-15e4-218d-c266013f8e28@kernel.dk> Date: Sat, 16 Nov 2019 09:57:06 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/16/19 12:17 AM, Masahiro Yamada wrote: > On Sat, Nov 16, 2019 at 8:10 AM Jens Axboe wrote: >> >> Hi, >> >> I've noticed that current -git is a lot slower at doing single object >> builds than earlier kernels. Here's an example, building the exact same >> file on 5.2 and -git: >> >> $ time make fs/io_uring.o >> real 0m5.953s >> user 0m5.402s >> sys 0m0.649s >> >> vs 5.2 based (with all the backports, identical file): >> >> $ time make fs/io_uring.o >> real 0m3.218s >> user 0m2.968s >> sys 0m0.520s >> >> Any idea what's going on here? It's almost twice as slow, which is >> problematic... > > > > This is necessary cost > to do single builds > (394053f4a4b3e3eeeaa67b67fc886a9a75bd9e4d) > but, it is much better in linux-next. Very sad that it's now twice as slow as before, that's a real problem. This isn't a marginal slowdown. I've never had issues with single object builds before, and in fact it's often useful to build stuff that's disabled as a single object. Where's the report that led to this commit being necessary? -- Jens Axboe