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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,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 524D1C2B9F4 for ; Tue, 22 Jun 2021 08:30:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 302C260C3E for ; Tue, 22 Jun 2021 08:30:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230384AbhFVIct (ORCPT ); Tue, 22 Jun 2021 04:32:49 -0400 Received: from imap2.colo.codethink.co.uk ([78.40.148.184]:38916 "EHLO imap2.colo.codethink.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229747AbhFVIcq (ORCPT ); Tue, 22 Jun 2021 04:32:46 -0400 Received: from cpc152649-stkp13-2-0-cust121.10-2.cable.virginm.net ([86.15.83.122] helo=[192.168.0.18]) by imap2.colo.codethink.co.uk with esmtpsa (Exim 4.92 #3 (Debian)) id 1lvbng-0006ij-CB; Tue, 22 Jun 2021 09:30:28 +0100 Subject: Re: [PATCH v2 0/5] riscv: improving uaccess with logs from network bench To: Akira Tsukamoto , Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org References: <5a5c07ac-8c11-79d3-46a3-a255d4148f76@gmail.com> From: Ben Dooks Organization: Codethink Limited. Message-ID: Date: Tue, 22 Jun 2021 09:30:26 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <5a5c07ac-8c11-79d3-46a3-a255d4148f76@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/06/2021 12:21, Akira Tsukamoto wrote: > Optimizing copy_to_user and copy_from_user. > > I rewrote the functions in v2, heavily influenced by Garry's memcpy > function [1]. > The functions must be written in assembler to handle page faults manually > inside the function. > > With the changes, improves in the percentage usage and some performance > of network speed in UDP packets. > Only patching copy_user. Using the original memcpy. > > All results are from the same base kernel, same rootfs and same > BeagleV beta board. > > Comparison by "perf top -Ue task-clock" while running iperf3. I did a quick test on a SiFive Unmatched with IO to an NVME. before: cached-reads=172.47MB/sec, buffered-reads=135.8MB/sec with-patch: cached-read=s177.54Mb/sec, buffered-reads=137.79MB/sec That was just one test run, so there was a small improvement. I am sort of surprised we didn't get more of a win from this. perf record on hdparm shows that it spends approx 15% cpu time in asm_copy_to_user. Does anyone have a benchmark for this which just looks at copy/to user? if not should we create one? -- Ben Dooks http://www.codethink.co.uk/ Senior Engineer Codethink - Providing Genius https://www.codethink.co.uk/privacy.html