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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 240EAC10F11 for ; Wed, 24 Apr 2019 05:58:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E20482148D for ; Wed, 24 Apr 2019 05:58:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="i4Sq/Oor" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729608AbfDXF6T (ORCPT ); Wed, 24 Apr 2019 01:58:19 -0400 Received: from mail-wm1-f67.google.com ([209.85.128.67]:40383 "EHLO mail-wm1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727018AbfDXF6T (ORCPT ); Wed, 24 Apr 2019 01:58:19 -0400 Received: by mail-wm1-f67.google.com with SMTP id z24so3150079wmi.5 for ; Tue, 23 Apr 2019 22:58:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:reply-to:from:date:message-id :subject:to:cc; bh=jqJCgAG38S0gDL9FZ3J1ce152B04bXKCfsxyJs81Cio=; b=i4Sq/Oor+EpdVNI9CJfT9Z5myfO/9yVnEBK1avuTyNZSPAhDkDC1N4dW6BIYSLVvM4 NV0Kcj21vqnB4EYAyVPDO05aTimC/R8MAWyMl2KaJrtPCDmQYgzGBIfvXq/mppipsJh3 e6kiVGefh6SpEUHGOuWhNat74nd8oD2BgPP6AJYezNTGSj7I7RNrLAsXAiIp6U0SVE44 L7nEf5hZkRmab3n8UxlBFOUBjCJ7hPJqIpruVX+/26ghj0AqQQG1Aw1AW4srM2r3mB5L LVCnpVowSfYpeyiEby78nh9BhJa6cW680j1d/DDywNZSdPXB6ZUNf/JG37IplE5Vc/8d BYqA== 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:reply-to :from:date:message-id:subject:to:cc; bh=jqJCgAG38S0gDL9FZ3J1ce152B04bXKCfsxyJs81Cio=; b=HRxqXmpiPA6WH3Dbx9nDpW2cblwPhXGRl3IqYnCo2bx7c48noW6vNZkzgnZx7IRVH7 P2plin7dWGtKC0i+QPYzngK6CN17QuadwVqke8zXKVfIF0nWohPN37FsqEDsW+I8CoHU C5SVyN69/R6aVWqRIFeetIRKQ5ghe1SvIoireRN8ZXwUykzeFXHHc2FvTOCx4Jml9blS Vvmv4Pf4nDbr6pRtgVBRh9Yib3mAOF00q5V3eqLoamUJyDhe3rsZQ/Pyy+nkdxV1YUVd ZbN/RLbPYPM80EswE4C8TStbEUNS3K97yGmFhY0WQrOzX4X5maBwEJgxtcCU1fdBHCNT NdlA== X-Gm-Message-State: APjAAAVFo2eCGpf6B/JzHXMBNIbrPVM3fczOKr6v0mjeF7GsOQGy2DsC 8KOnsXWzfF65MfupAFNxW3PlyrtWTdUrD3R8QSI= X-Google-Smtp-Source: APXvYqxw1aswtoX4DVUxy1+M3ZmnqtUBnXmBabche6WGQb88gJCjlhsgNXNKRPFUCB0WtcXN+iNKUNSG3sACMsiVXOE= X-Received: by 2002:a1c:80c1:: with SMTP id b184mr5071368wmd.109.1556085497214; Tue, 23 Apr 2019 22:58:17 -0700 (PDT) MIME-Version: 1.0 References: <20190423190426.18720-1-natechancellor@gmail.com> <20190423193512.GP17719@sasha-vm> <20190423194512.GA31444@archlinux-i9> <20190423195628.GD112750@google.com> <20190423200355.GA17824@archlinux-i9> <20190423234608.GU17719@sasha-vm> In-Reply-To: <20190423234608.GU17719@sasha-vm> Reply-To: sedat.dilek@gmail.com From: Sedat Dilek Date: Wed, 24 Apr 2019 07:58:05 +0200 Message-ID: Subject: Re: Backport of commit a75bb4eb9e565b9f5115e2e8c07377ce32cbe69a To: Sasha Levin Cc: Nathan Chancellor , Matthias Kaehlcke , Greg Kroah-Hartman , stable@vger.kernel.org, Nick Desaulniers , Clang-Built-Linux ML Content-Type: text/plain; charset="UTF-8" Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Wed, Apr 24, 2019 at 1:46 AM Sasha Levin wrote: > > On Tue, Apr 23, 2019 at 01:03:55PM -0700, Nathan Chancellor wrote: > >On Tue, Apr 23, 2019 at 12:56:28PM -0700, Matthias Kaehlcke wrote: > >> On Tue, Apr 23, 2019 at 12:45:12PM -0700, Nathan Chancellor wrote: > >> > On Tue, Apr 23, 2019 at 03:35:12PM -0400, Sasha Levin wrote: > >> > > On Tue, Apr 23, 2019 at 12:04:21PM -0700, Nathan Chancellor wrote: > >> > > > Hi Greg and Sasha, > >> > > > > >> > > > Please apply this commit to 4.4 through 5.0 (patches are threaded in > >> > > > reply to this one), which will prevent Clang from emitting references > >> > > > to compiler runtime functions and doing some performance-killing > >> > > > optimization when using CONFIG_CC_OPTIMIZE_FOR_SIZE. > >> > > > > >> > > > Please let me know if I did something wrong or if there are any > >> > > > objections. > >> > > > >> > > This looks like a fix for a performance regression, which don't usually > >> > > end up in stable unless they are severe enough. > >> > > > >> > > >> > Yes and no. The original reason for the revert was because of the > >> > compiler runtime functions: > >> > > >> > https://lore.kernel.org/lkml/CAG5bF+S6OvBnsaR6UpMCqjDR9_hMo6qRMHGiW+iCaRYQW4C3YA@mail.gmail.com/ > >> > > >> > The Chromium guys hit this [1] and have applied the patch for their > >> > kernels, I think it should be applied for everyone. > >> > >> We picked it into our kernels because we needed a fix *now* to unbreak > >> our builds, but I agree it should be fixed at least in relevant LTS > >> versions. > >> > > > >Of course, I wasn't implying that was a bad thing :) it's further > >justification for this being a stable worthy patch as it fixes a real > >world issue and could fix more. > > Okay, this makes more sense. The upstream commit message failed to > mention this. > > I've queued it up. > Dropped my private for-5.0/kbuild-cc-optimization Git branch. One less patch to carry with me... Thanks. - Sedat -