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 6FE6CC282C3 for ; Thu, 24 Jan 2019 09:43:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 14F0320855 for ; Thu, 24 Jan 2019 09:43:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="a9cRoELF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727420AbfAXJnw (ORCPT ); Thu, 24 Jan 2019 04:43:52 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:10118 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726012AbfAXJnw (ORCPT ); Thu, 24 Jan 2019 04:43:52 -0500 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 43lcfs24ctz9v0GN; Thu, 24 Jan 2019 10:43:49 +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=a9cRoELF; 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 qerfoCtk40gn; Thu, 24 Jan 2019 10:43:49 +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 43lcfs0jGJz9v0GM; Thu, 24 Jan 2019 10:43:49 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1548323029; bh=pdpzN4Cls9VIi57rwmgYgmW1ymLGgOvDPZus6sPQUOw=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=a9cRoELFwxDif1NC2YT2l165rRga4QNBnkYLLw3lLr06pUcnaKGhX5ZgZuGt1m98b NS1ZYi6k3427XVB/4aIqzh6C85pBbZCmP2zcUloJuk8vxpgtbj5ppWRIftd20dfeie Dswq3SPH6SpkCh0W3SzrlZcENjGXogSHvb9q7ZxU= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 3629D8B838; Thu, 24 Jan 2019 10:43:50 +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 P6qvuZTZhQ0g; Thu, 24 Jan 2019 10:43:50 +0100 (CET) Received: from po16846vm.idsi0.si.c-s.fr (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id A582A8B755; Thu, 24 Jan 2019 10:43:49 +0100 (CET) Subject: Re: [PATCH v13 00/10] powerpc: Switch to CONFIG_THREAD_INFO_IN_TASK To: Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Nicholas Piggin Cc: Mike Rapoport , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <2e700e1c-5bd9-652e-b535-68a89dd703a1@c-s.fr> <87y37ax3ru.fsf@concordia.ellerman.id.au> From: Christophe Leroy Message-ID: <9b4dab64-6a6b-a599-4676-bf891473ada7@c-s.fr> Date: Thu, 24 Jan 2019 09:43:47 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <87y37ax3ru.fsf@concordia.ellerman.id.au> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 ? I run null_syscall with perf, and I get the following. Can we conclude on something with that ? Without the serie: # Overhead Samples Command Shared Object Symbol # ........ ............ ............ ................. ........................................ # 32.95% 46375 null_syscall [kernel.kallsyms] [k] DoSyscall 23.64% 33275 null_syscall [kernel.kallsyms] [k] __task_pid_nr_ns 15.47% 21778 null_syscall libc-2.23.so [.] __GI___getppid 8.92% 12556 null_syscall [kernel.kallsyms] [k] __rcu_read_unlock 5.69% 8014 null_syscall [kernel.kallsyms] [k] sys_getppid 4.01% 5643 null_syscall [kernel.kallsyms] [k] __rcu_read_lock 3.67% 5166 null_syscall [kernel.kallsyms] [k] syscall_dotrace_cont 2.52% 3542 null_syscall null_syscall [.] main With the serie: 30.04% 56337 null_syscall [kernel.kallsyms] [k] DoSyscall 13.89% 26060 null_syscall [kernel.kallsyms] [k] __rcu_read_unlock 13.36% 25062 null_syscall libc-2.23.so [.] __GI___getppid 12.73% 23872 null_syscall [kernel.kallsyms] [k] __task_pid_nr_ns 11.21% 21033 null_syscall [kernel.kallsyms] [k] sys_getppid 8.24% 15457 null_syscall [kernel.kallsyms] [k] syscall_dotrace_cont 4.38% 8217 null_syscall [kernel.kallsyms] [k] ret_from_syscall 2.54% 4773 null_syscall null_syscall [.] main Christophe