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=-4.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, TVD_SUBJ_WIPE_DEBT,URIBL_BLOCKED,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 4D57FC433DF for ; Tue, 18 Aug 2020 18:06:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 240F3206B5 for ; Tue, 18 Aug 2020 18:06:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726635AbgHRSF7 (ORCPT ); Tue, 18 Aug 2020 14:05:59 -0400 Received: from verein.lst.de ([213.95.11.211]:34545 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726145AbgHRSF6 (ORCPT ); Tue, 18 Aug 2020 14:05:58 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id C0BB768AFE; Tue, 18 Aug 2020 20:05:55 +0200 (CEST) Date: Tue, 18 Aug 2020 20:05:55 +0200 From: Christoph Hellwig To: Christophe Leroy Cc: Christoph Hellwig , Al Viro , Michael Ellerman , x86@kernel.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Kees Cook , linux-kernel@vger.kernel.org Subject: Re: remove the last set_fs() in common code, and remove it for x86 and powerpc Message-ID: <20200818180555.GA29185@lst.de> References: <20200817073212.830069-1-hch@lst.de> <319d15b1-cb4a-a7b4-3082-12bb30eb5143@csgroup.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <319d15b1-cb4a-a7b4-3082-12bb30eb5143@csgroup.eu> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Aug 18, 2020 at 07:46:22PM +0200, Christophe Leroy wrote: > I gave it a go on my powerpc mpc832x. I tested it on top of my newest > series that reworks the 32 bits signal handlers (see > https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=196278) with > the microbenchmark test used is that series. > > With KUAP activated, on top of signal32 rework, performance is boosted as > system time for the microbenchmark goes from 1.73s down to 1.56s, that is > 10% quicker > > Surprisingly, with the kernel as is today without my signal's series, your > series degrades performance slightly (from 2.55s to 2.64s ie 3.5% slower). > > > I also observe, in both cases, a degradation on > > dd if=/dev/zero of=/dev/null count=1M > > Without your series, it runs in 5.29 seconds. > With your series, it runs in 5.82 seconds, that is 10% more time. That's pretty strage, I wonder if some kernel text cache line effects come into play here? The kernel access side is only used in slow path code, so it should not make a difference, and the uaccess code is simplified and should be (marginally) faster. Btw, was this with the __{get,put}_user_allowed cockup that you noticed fixed?