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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6E49C43334 for ; Fri, 17 Jun 2022 19:34:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242571AbiFQTeR (ORCPT ); Fri, 17 Jun 2022 15:34:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47474 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241748AbiFQTeN (ORCPT ); Fri, 17 Jun 2022 15:34:13 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6D97E57B31; Fri, 17 Jun 2022 12:34:07 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id CC4C6CE2CE5; Fri, 17 Jun 2022 19:34:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9133AC3411B; Fri, 17 Jun 2022 19:34:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1655494444; bh=iGbceJbT8v7gImOkGLsLLbOe6rqxDg6MXNzjf6wMTlE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Tr+mboi+5Q+1X6yERhmLUcPCoKaCo2o6pwAJtIXvNbyRKoH1Mod1CV/k3UuHSbkZN 01Ba15USpGkIWGRvKxhJ+uMDiOi99sn/Kue56xTqG75aGZCUQ/cToelqXwODW3X97a cBlpvobQr+WUDkIQzx1+UDWNWZ+w2I4ssLbOZu2ExfQTS4+ft2ONW3AiZnOJ5QzEqS zrZxyEo2qgO5l4Hannpw80+3uFH09mROeN1NoQrt57yxi/foSc02I3dFtngtGFrHXu br2oUouVBfjvg2ifOBWoyd22GXPsUkcZKeDqRMs/aqa0tvEa/vr+MFhWN3EVLnx43F FLqHMWGpnrPbw== Date: Fri, 17 Jun 2022 12:34:01 -0700 From: Nathan Chancellor To: Sedat Dilek Cc: Nick Desaulniers , Masahiro Yamada , Jiri Slaby , Linux Kbuild mailing list , LKML , Michal Marek , Sami Tolvanen Subject: Re: [PATCH] kbuild: pass jobserver to cmd_ld_vmlinux.o Message-ID: References: <20220616104541.16289-1-jslaby@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org On Fri, Jun 17, 2022 at 07:50:58PM +0200, Sedat Dilek wrote: > On Fri, Jun 17, 2022 at 6:32 PM Nick Desaulniers > wrote: > > > > On Fri, Jun 17, 2022 at 3:35 AM Sedat Dilek wrote: > > > > > > On Fri, Jun 17, 2022 at 12:53 AM Sedat Dilek wrote: > > > > > > > > On Thu, Jun 16, 2022 at 4:09 PM Sedat Dilek wrote: > > > > > > > > > > On Thu, Jun 16, 2022 at 12:45 PM Jiri Slaby wrote: > > > > > > > > > > > > Until the link-vmlinux.sh split (cf. the commit below), the linker was > > > > > > run with jobserver set in MAKEFLAGS. After the split, the command in > > > > > > Makefile.vmlinux_o is not prefixed by "+" anymore, so this information > > > > > > is lost. > > > > > > > > > > > > Restore it as linkers working in parallel (esp. the LTO ones) make a use > > > > > > of it. > > > > TBH, I agree with Masahiro. I didn't understand this comment "esp. the > > LTO ones." Jiri, can you clarify what you mean here? > > > > > [ CC Nathan and Sami ] > > > > > > I re-checked as my build-time takes approx. 15mins more than usual > > > with Linux v5.17. > > > > > > [ Perf - seconds time elapsed ] > > > v5.17: approx. 12500 > > > v5.19: approx. 13500 > > > > > > +1.000 secs = +16,67mins So roughly 7.5% increase if I did my math correctly? > > Does this patch make a difference? > > https://lore.kernel.org/linux-kbuild/20220616195759.3214538-1-samitolvanen@google.com/ > > > > Running a new build... I did a quick benchmark with Fedora's clang 14.0.0 and I didn't see an increase of that proportion with your configuration (only about 1%, which I would expect would be within the noise for new drivers and such): Benchmark 1: 5.17 Time (abs ≡): 287.744 s [User: 23497.818 s, System: 4444.602 s] Benchmark 2: 5.19-rc2 Time (abs ≡): 290.027 s [User: 24567.290 s, System: 4834.458 s] Summary '5.17' ran 1.01 times faster than '5.19-rc2' Not to say that there is not an issue but it might be more visible with slower hardware. Cheers, Nathan