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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED 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 8E44FC282C3 for ; Thu, 24 Jan 2019 15:02:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 617A321872 for ; Thu, 24 Jan 2019 15:02:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="AWXy66uF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728478AbfAXPCC (ORCPT ); Thu, 24 Jan 2019 10:02:02 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:41753 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727755AbfAXPCC (ORCPT ); Thu, 24 Jan 2019 10:02:02 -0500 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 43lljz0rgNz9txl5; Thu, 24 Jan 2019 16:01:59 +0100 (CET) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=AWXy66uF; dkim-adsp=pass; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id svVl3c25HCxp; Thu, 24 Jan 2019 16:01:59 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 43lljy6KpJz9txl1; Thu, 24 Jan 2019 16:01:58 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1548342118; bh=8/nTswzcnLkOu6savh5/oxVwW7VmvzVbzz91aQOIlG0=; h=Subject:From:To:Cc:References:Date:In-Reply-To:From; b=AWXy66uF7UqUvu7z9+OHB74HZriF9v0227onlwMRQGJXepIzn7KqNw4ye+66mN+FR Kp4q0ztaW4Bh1oOy7gAujoxfru3I9UWmCW03FSey5l2k7qvp7PunWieL6S3KAqMaLC k+IVDge8SbVoYDntTfFjkcEhVQcJp23ah/SPjISM= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 5D9EA8B85C; Thu, 24 Jan 2019 16:02:00 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id OgiZWwENdL3N; Thu, 24 Jan 2019 16:02:00 +0100 (CET) Received: from PO15451 (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id DF1798B850; Thu, 24 Jan 2019 16:01:59 +0100 (CET) Subject: Re: [PATCH v13 00/10] powerpc: Switch to CONFIG_THREAD_INFO_IN_TASK From: Christophe Leroy To: Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Nicholas Piggin Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Mike Rapoport References: <2e700e1c-5bd9-652e-b535-68a89dd703a1@c-s.fr> <87y37ax3ru.fsf@concordia.ellerman.id.au> <9b4dab64-6a6b-a599-4676-bf891473ada7@c-s.fr> Message-ID: Date: Thu, 24 Jan 2019 16:01:59 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <9b4dab64-6a6b-a599-4676-bf891473ada7@c-s.fr> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 24/01/2019 à 10:43, Christophe Leroy a écrit : > > > On 01/24/2019 01:06 AM, Michael Ellerman wrote: >> Christophe Leroy writes: >>> Le 12/01/2019 à 10:55, Christophe Leroy a écrit : >>>> The purpose of this serie is to activate CONFIG_THREAD_INFO_IN_TASK >>>> which >>>> moves the thread_info into task_struct. >>>> >>>> Moving thread_info into task_struct has the following advantages: >>>> - It protects thread_info from corruption in the case of stack >>>> overflows. >>>> - Its address is harder to determine if stack addresses are >>>> leaked, making a number of attacks more difficult. >>> >>> I ran null_syscall and context_switch benchmark selftests and the result >>> is surprising. There is slight degradation in context_switch and a >>> significant one on null_syscall: >>> >>> Without the serie: >>> >>> ~# chrt -f 98 ./context_switch --no-altivec --no-vector --no-fp >>> 55542 >>> 55562 >>> 55564 >>> 55562 >>> 55568 >>> ... >>> >>> ~# ./null_syscall >>>      2546.71 ns     336.17 cycles >>> >>> >>> With the serie: >>> >>> ~# chrt -f 98 ./context_switch --no-altivec --no-vector --no-fp >>> 55138 >>> 55142 >>> 55152 >>> 55144 >>> 55142 >>> >>> ~# ./null_syscall >>>      3479.54 ns     459.30 cycles >>> >>> So 0,8% less context switches per second and 37% more time for one >>> syscall ? >>> >>> Any idea ? >> >> What platform is that on? > > It is on the 8xx > >> >> On 64-bit we have to turn one mtmsrd into two and that's obviously a >> slow down. But I don't see that you've done anything similar in 32-bit >> code. >> >> I assume it's patch 8 that causes the slow down? > > I have not digged into it yet, but why patch 8 ? > The increase of null_syscall duration happens with patch 5 when we activate CONFIG_THREAD_INFO_IN_TASK. Christophe