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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 2BC48C43603 for ; Wed, 4 Dec 2019 23:46:20 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id F36CD206DB for ; Wed, 4 Dec 2019 23:46:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="rrpeEucT"; dkim=fail reason="signature verification failed" (2048-bit key) header.d=brainfault-org.20150623.gappssmtp.com header.i=@brainfault-org.20150623.gappssmtp.com header.b="xAwbsMb9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F36CD206DB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=brainfault.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:To: Subject:Message-ID:Date:From:In-Reply-To:References:MIME-Version:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=LyGjF/rkwWS2ExVqCvEb3Z2JEo92ZJuKNi25eoJBxHc=; b=rrpeEucTfbZaTNR+rtJKKWI5J X246WYhke9YQfRpKnRUnHz4d72LH+JMdxyGiqA7vUDl76DGPLjMeAwLlkzkc4gXDkfpVLNp5Kmsk4 gBvyK/9dX7umigRuwa4+n5P/gWEA1wly+es9SO22XoemYoWcg9NaTn1TSunWIMmvLozkOE61PccXC xr/vviuBRZX8qIiFOfgHIMFQLe7A2z7FGWoysjhHlwzqX7l8WBhJr9fMamPi+wLtv7TbxGWYAQQ21 mIUkJdwlzLOYIDsH6lCg0lazJ9k4TIen93Qn2vloSE+6gytbjh85hA8xMkuXg0qKvUDkUny9g/Lnk IWc1+WKWg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iceLa-0007kL-Ol; Wed, 04 Dec 2019 23:46:18 +0000 Received: from mail-wr1-x442.google.com ([2a00:1450:4864:20::442]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iceLW-0007dP-L0 for linux-riscv@lists.infradead.org; Wed, 04 Dec 2019 23:46:16 +0000 Received: by mail-wr1-x442.google.com with SMTP id t2so1316750wrr.1 for ; Wed, 04 Dec 2019 15:46:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=brainfault-org.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=LyGjF/rkwWS2ExVqCvEb3Z2JEo92ZJuKNi25eoJBxHc=; b=xAwbsMb9aGoP+r+OnPfZiWzavaYkWeAUkslEMZ5t8lulO827ECG9YLZf/4V0X+QTEq +fcAR+I+bFz4gn4MgmF6Yjcmar85AxQ34GcwUGYxKDUcJtIJSkrmVANDtIOAhqkp8oMD Umbje+bIHdpMhEoASH2A34tyT6xaMolpvsghDsXwE1Sxj2C4j9hwo8wYDws8fYkzbgt/ Wsj9pB2I7lqJgzBJfRp7L+wIx5B6zNkNVMIUU8tE97/hdKBFnWBBw4VYnojJ011/3+P0 wG+y3keXvprViGb2tt+aM5E/QqCDAxI/NachcjtP/whXFNEH+qBqGeZHsTbvUUdl5Aq2 cxjg== 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:from:date :message-id:subject:to:cc; bh=LyGjF/rkwWS2ExVqCvEb3Z2JEo92ZJuKNi25eoJBxHc=; b=qiCO8ttLXhkBQKBAsXD9yFGdupcOdeJWYV8Ap0CaHmo1PzwC8fVzPjeJXKJarkKBT/ Cb9WT5auq3yT26koJb6tqvmtDcRhI8W79b+OMkmwqvEbymlOtZ+Mn2XlmHp8UVdAVmVp jLEEEPwktJ3ak02MVR1dCbmUe1din56G9SZ0wTU7YWKn6uh/r7prLsiMotVMW7egvS/B /8Op6TtBkUJx7dkzA3ECYm5W+CIdkVByHr5SrM+WXEFmPFbH9gCocxE8l41VSe4vNexi v2ScmmG2BCDYn+xOd8yp1zgmMSb4oT0vHwJiJM1bo6QLKd5b+Bd2WwXPH0cGtWtfIAox 4WRQ== X-Gm-Message-State: APjAAAWgZwrzIi7y/t7MXr6i7at/NwUquOiCp3iwpYcwuZwpkFd9Y0a+ 4qaDCNSjzDOlinIrHa/WDbWMGxew6R2cDZhbFpEfqQ== X-Google-Smtp-Source: APXvYqzbuVfNGh5XRBrOq8FbFMia6iU8j+JSQQYBokkifbU6uegHzqiCIV16VOfXrmTaR5k6tR5UELbQb5Ra2iDYlqk= X-Received: by 2002:adf:d850:: with SMTP id k16mr6450667wrl.96.1575503172158; Wed, 04 Dec 2019 15:46:12 -0800 (PST) MIME-Version: 1.0 References: <9044bad02aa6553cdb2523294500b50fccf3fd2a.camel@wdc.com> <81530734312456aab8b9625d7e9bb071c43db1c5.camel@wdc.com> In-Reply-To: <81530734312456aab8b9625d7e9bb071c43db1c5.camel@wdc.com> From: Anup Patel Date: Thu, 5 Dec 2019 05:16:00 +0530 Message-ID: Subject: Re: [GIT PULL] Second set of RISC-V updates for v5.5-rc1 To: Alistair Francis Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191204_154614_868504_4092D1FF X-CRM114-Status: GOOD ( 18.09 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "linux-kernel@vger.kernel.org" , Atish Patra , "paul.walmsley@sifive.com" , "linux-riscv@lists.infradead.org" , "torvalds@linux-foundation.org" , "hch@lst.de" Sender: "linux-riscv" Errors-To: linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org On Thu, Dec 5, 2019 at 1:20 AM Alistair Francis wrote: > > On Wed, 2019-12-04 at 11:38 -0800, Paul Walmsley wrote: > > Alistair, Anup, > > > > On Wed, 4 Dec 2019, Alistair Francis wrote: > > > > > On Wed, 2019-12-04 at 18:22 +0530, Anup Patel wrote: > > > > > > > I had commented on your patch but my comments are still > > > > not addressed. > > > > > > > > Various debug options enabled by this patch have performance > > > > impact. Instead of enabling these debug options in primary > > > > defconfigs, I suggest to have separate debug defconfigs with > > > > these options enabled. > > > > > > +1 > > > > > > OE uses the defconfig (as I'm sure other distros do) and slowing > > > down > > > users seems like a bad idea. > > > > While I respect your points of view, our defconfigs are oriented > > towards > > kernel developers. This is particularly important when right now the > > only > > That is just not what happens though. > > It is too much to expect every distro to maintain a defconfig for RISC- > V. There are constantly new features that need to be enabled/disabled > in the configs and it isn't always clear to outsiders. Which is why we > currently use the defconfig as a base and apply extra features that > distro want on top. > > Expecting every distro to have a kernel developers level of knowledge > about configuring Kconfigs is just unrealistic. > > > RISC-V hardware on the market are test chips. Our expectation is > > that > > Treating RISC-V as a test architecture seems like a good way to make > sure that is all it ever is. > > > distros and benchmarkers will create their own Kconfigs for their > > needs. > > Like I said, that isn't true. After this patch is applied (and it makes > it to a release) all OE users will now have a slower RISC-V kernel. > This also applies to buildroot and probably other distos. > > Now image some company wants to investigate using a RISC-V chip for > their embedded project. They use OE/buildroot to build a quick test > setup and boot Linux. It now runs significantly slower then some other > architecture and they don't choose RISC-V. > > Slowing down all users to help kernel developers debug seems like the > wrong direction. Kernel developers should know enough to be able to > turn on the required configs, why does this need to be the default? I quickly tried hackbench on SiFive Unleashed board with latest Linus tree master branch (having your patch) and I am seeing 12% slowdown. I am sure if I try more heavier benchmarks (such as stress-ng) then the slowdown will be even more. Here are the detailed numbers: Command: ./hackbench 32 Number of Tasks: 32*40 (== 1280) Average Time (without debug options): 3.10525 Average Time (with debug options): 3.471 (11.78% slower) Command: ./hackbench 64 Number of Tasks: 64*40 (== 2560) Average Time (without debug options): 6.3015 Average Time (with debug options): 7.05875 (12.017% slower) Command: ./hackbench 128 Number of Tasks: 128*40 (== 5120) Average Time (without debug options): 12.6275 Average Time (with debug options): 14.1455 (12.0214% slower) It is this performance impact due to which other architectures (such as x86 and ARM64) don't have these debug options enabled in their defconfigs. I will send a patch to move these debug options to separate debug defconfigs so that people have a way to build a debug kernel. Regards, Anup