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 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 DB668C282C3 for ; Thu, 24 Jan 2019 15:58:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A87CE218B0 for ; Thu, 24 Jan 2019 15:58:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="qgiyViNK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728754AbfAXP6p (ORCPT ); Thu, 24 Jan 2019 10:58:45 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:57910 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727649AbfAXP6o (ORCPT ); Thu, 24 Jan 2019 10:58:44 -0500 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 43lmzP1VDRz9v0B9; Thu, 24 Jan 2019 16:58:41 +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=qgiyViNK; 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 Mgc1uuGNV8-q; Thu, 24 Jan 2019 16:58:41 +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 43lmzP064pz9v0B6; Thu, 24 Jan 2019 16:58:41 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1548345521; bh=ssyC1duNx4bdJMAAoq9xbUOfPZYMyfEtKvK1EJUeh5k=; h=Subject:From:To:Cc:References:Date:In-Reply-To:From; b=qgiyViNK7Xs4K8iZzdY7m2TdvEdZHh67H9GSrcSGTDupERs+0equL7n+r9bytJvpk CikwgtMqNxMv32fQthBOjs4yutswUinkX3cenZSiEbOV0m5MejEFHFtVS+UCZ8utaX q023CENUtTei995Tqw/lrVMhAk8+J0zKHN6W/hoI= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 8A3198B85E; Thu, 24 Jan 2019 16:58:42 +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 dwa_Gkl4usaG; Thu, 24 Jan 2019 16:58:42 +0100 (CET) Received: from PO15451 (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 0F9448B850; Thu, 24 Jan 2019 16:58:42 +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: <89049465-643f-b383-82e2-360dc9660d09@c-s.fr> Date: Thu, 24 Jan 2019 16:58:41 +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: 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 16:01, Christophe Leroy a écrit : > > > 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 the 83xx, I have a slight improvment: Without the serie: root@vgoippro:~# ./null_syscall 921.44 ns 307.15 cycles With the serie: root@vgoippro:~# ./null_syscall 918.78 ns 306.26 cycles Christophe >> >>> >>> 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. >