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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 A91F5C2BA15 for ; Sun, 5 Apr 2020 18:53:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7B9D020659 for ; Sun, 5 Apr 2020 18:53:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="eJQ3oG1e" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727548AbgDESxj (ORCPT ); Sun, 5 Apr 2020 14:53:39 -0400 Received: from pegase1.c-s.fr ([93.17.236.30]:23813 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726771AbgDESxj (ORCPT ); Sun, 5 Apr 2020 14:53:39 -0400 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 48wN9T41YPz9tx5x; Sun, 5 Apr 2020 20:53:33 +0200 (CEST) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=eJQ3oG1e; 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 rPwFmN31zfvx; Sun, 5 Apr 2020 20:53:33 +0200 (CEST) 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 48wN9T2t7Vz9tx5w; Sun, 5 Apr 2020 20:53:33 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1586112813; bh=90bPcvM3Kr4KjzMKiGYjpWqCbKmKJ+xpkekjY3cVUhQ=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=eJQ3oG1ebDmiDGHzDikOxVWGvPigmsoEYiiyN/LJjcvcAHCs4LnhNB82kOiD64ME5 Elaf5u+hqdwsLi6oguAVkE6PJtJeYrWZSxeAUWZxYNWo3NcWi/U05qkcI+PI32sk9N gW96UdqFlzinI2CilHJOhz7SUFwqZOxYC/XBEvE4= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 11BA08B783; Sun, 5 Apr 2020 20:53:37 +0200 (CEST) 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 QxPOLoXO54EU; Sun, 5 Apr 2020 20:53:37 +0200 (CEST) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 200BC8B774; Sun, 5 Apr 2020 20:53:36 +0200 (CEST) Subject: Re: [RFC WIP PATCH] powerpc/32: system call implement entry/exit logic in C To: Nicholas Piggin , Benjamin Herrenschmidt , Michael Ellerman , msuchanek@suse.de, Paul Mackerras Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <059c1abd-6be2-25ea-83e0-dcd411b7951b@c-s.fr> <1585898897.1jwur86s6a.astroid@bobo.none> From: Christophe Leroy Message-ID: Date: Sun, 5 Apr 2020 20:53:00 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <1585898897.1jwur86s6a.astroid@bobo.none> 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 03/04/2020 à 09:33, Nicholas Piggin a écrit : > Christophe Leroy's on April 1, 2020 9:48 pm: >> >> >> Le 31/03/2020 à 17:22, Christophe Leroy a écrit : >>> That's first try to port PPC64 syscall entry/exit logic in C to PPC32. >>> I've do the minimum to get it work. I have not reworked calls >>> to sys_fork() and friends for instance. >>> >>> For the time being, it seems to work more or less but: >>> - ping reports EINVAL on recvfrom >>> - strace shows NULL instead of strings in call like open() for instance. >> >> For the two above problems, that's because system_call_exception() >> doesn't set orig_gpr3 whereas DoSycall() does in entry_32.S . Is that >> only done on PPC32 ? >> >> With the following line at the begining of system_call_exception(), it >> works perfectly: >> >> regs->orig_gpr3 = r3; > > Oh great, nice work. We should be able to make some simple helpers or > move some things a bit to reduce the amount of ifdefs in the C code. > It doesn't look too bad though. > >> I will now focus on performance to see if we can do something about it. > > What's the performance difference between current asm code just with > always saving NVGPRS vs C? Done new measurement and sent a series. lower values now because the time accounting was done twice as it was still in the ASM part. Before the series, 311 cycles for a null_syscall If adding SAVE_NVGPRS to the entry macro, 335 cycles First patch: 353 cycles ie +13,5% After a few changes, including conditional saving of non volatile registers, I get 325 cycles that is only +4,5%. I thing that's acceptable. Do you see a problem with still saving non volatile registers only when required ? Christophe