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=-0.7 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, 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 76A77C432C0 for ; Mon, 18 Nov 2019 00:41:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4D15020730 for ; Mon, 18 Nov 2019 00:41:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nifty.com header.i=@nifty.com header.b="1/qD5nxS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726475AbfKRAk7 (ORCPT ); Sun, 17 Nov 2019 19:40:59 -0500 Received: from conssluserg-02.nifty.com ([210.131.2.81]:33508 "EHLO conssluserg-02.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726297AbfKRAk7 (ORCPT ); Sun, 17 Nov 2019 19:40:59 -0500 Received: from mail-vs1-f44.google.com (mail-vs1-f44.google.com [209.85.217.44]) (authenticated) by conssluserg-02.nifty.com with ESMTP id xAI0ergl002444 for ; Mon, 18 Nov 2019 09:40:53 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-02.nifty.com xAI0ergl002444 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1574037653; bh=hkPXAic6NPXzq/7n9TnXGwIxJXxKUEf9zWj/n2i4rVo=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=1/qD5nxSDwXF1BVmUT9IpqlkLvAHWLYNaJbr3FI8wYTJZ0x7Rp8PQNomHYw32jQms DFe0e39+F0v2g52Mdb3bWXovwb3fTl/piX7lu8aaNOwjmToXGYAUx2YCUDNip8T9Ra Zc6jH2F5dCFER5Rq6B4Y4U1WzGdh9YC9gijXGajqDIQWl/ATp9cCbbnCwpGL8jfJHC kmvE2N8MFtGwzsR8rDRQ3dA/UufIvoXl4V5TRmUqV4o5ZtLM1cLJk5Aweqvz3YKIkE 3JZw0A9AWq9RVOStHNFpWQyPX1KFwDJPAbFSvLlppbVkuYl3PrVDFX95pe4Z+mzOJJ cjnHtC02CB0Vg== X-Nifty-SrcIP: [209.85.217.44] Received: by mail-vs1-f44.google.com with SMTP id m9so10329848vsq.7 for ; Sun, 17 Nov 2019 16:40:53 -0800 (PST) X-Gm-Message-State: APjAAAVwyqyy3jLxbbLvn+jkGHxK+8KvOjFeXyoca1FdQpPVzeoK00eF JWM8irE756A/PWj/Ex/gFI58nlTFpNVTfsUJlm8= X-Google-Smtp-Source: APXvYqybItcVCM2CCmBWq1V7TdcCN/76kG/hMiER2uQuDKycdTQXOFIQR22XfA0AhTNxDemt7wu288YiJbparz92QTY= X-Received: by 2002:a05:6102:3204:: with SMTP id r4mr12870949vsf.181.1574037652398; Sun, 17 Nov 2019 16:40:52 -0800 (PST) MIME-Version: 1.0 References: <8caa1edf-9c6f-15e4-218d-c266013f8e28@kernel.dk> In-Reply-To: <8caa1edf-9c6f-15e4-218d-c266013f8e28@kernel.dk> From: Masahiro Yamada Date: Mon, 18 Nov 2019 09:40:16 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: Recent slowdown in single object builds To: Jens Axboe Cc: "linux-kernel@vger.kernel.org" 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, Nov 17, 2019 at 1:57 AM Jens Axboe wrote: > > 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... BTW, I am using a cheap machine based on Intel Core i7-6700K. I can build fs/io_uring.o (based on x86_64_defconfig) much faster. The slowdown (1.990 sec -> 2.861 sec) is not terrible for me. masahiro@pug:~/ref/linux$ git describe v5.2 masahiro@pug:~/ref/linux$ touch fs/io_uring.c; time make fs/io_uring.o CALL scripts/checksyscalls.sh CALL scripts/atomic/check-atomics.sh DESCEND objtool CC fs/io_uring.o real 0m1.990s user 0m1.723s sys 0m0.427s masahiro@pug:~/ref/linux-next$ git describe next-20191115 masahiro@pug:~/ref/linux-next$ touch fs/io_uring.c; time make fs/io_uring.o CALL scripts/checksyscalls.sh CALL scripts/atomic/check-atomics.sh DESCEND objtool CC fs/io_uring.o real 0m2.861s user 0m2.373s sys 0m0.642s Snippet from my /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 94 model name : Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz stepping : 3 microcode : 0xd4 cpu MHz : 800.023 cache size : 8192 KB > > > > > > 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 > -- Best Regards Masahiro Yamada