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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 4F232C10F03 for ; Tue, 23 Apr 2019 19:35:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 20287218B0 for ; Tue, 23 Apr 2019 19:35:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556048115; bh=uq1yVdbKKMXFoR7RxLtOwULeozVBm0hOb8+pVMGYrdE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=1z3ztIzxIT2zrEf+vd1gSHsxO26bxVt+GuF691IPSP53fv8fafptqYbzg1RFz64Kl 7rCUQYiI441OvaHYfUOuDP0DwVNN/OJA/muzTGkn9bCFD+j3DeAeydjt+TQ3W1i6MB mKNvSV9D1dBBaPkLD66Qe1ledFMK85iAcPmjYRiw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726018AbfDWTfO (ORCPT ); Tue, 23 Apr 2019 15:35:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:54520 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725945AbfDWTfO (ORCPT ); Tue, 23 Apr 2019 15:35:14 -0400 Received: from localhost (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8A4B521738; Tue, 23 Apr 2019 19:35:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556048113; bh=uq1yVdbKKMXFoR7RxLtOwULeozVBm0hOb8+pVMGYrdE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=xzVav5XpLytYRIHZsSN/mHyffVrUROq551lLB+h2qp0BpecIBKXxyG0NmR1qxUuS+ amt8tto91H+fwBmSNi6gOQxZNiWoPSKNUBDu4QOsVDJFxS1heSmxIo0Fb3e7SWRYi1 +ErsUpwt5m2Lf1YbjjeWoLr2QhH41toSxR1cVWb0= Date: Tue, 23 Apr 2019 15:35:12 -0400 From: Sasha Levin To: Nathan Chancellor Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Nick Desaulniers , clang-built-linux@googlegroups.com Subject: Re: Backport of commit a75bb4eb9e565b9f5115e2e8c07377ce32cbe69a Message-ID: <20190423193512.GP17719@sasha-vm> References: <20190423190426.18720-1-natechancellor@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20190423190426.18720-1-natechancellor@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 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. This patch looks simple enough, and seeing peterz on it suggests to me that this was significant enough for someone to notice. Is this really the case, or is this just one of those %0.01 performance regression things? -- Thanks, Sasha