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[217.178.128.163]) by smtp.gmail.com with ESMTPSA id c68sm5923987pfc.75.2021.06.22.05.05.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Jun 2021 05:05:29 -0700 (PDT) Subject: Re: [PATCH v2 0/5] riscv: improving uaccess with logs from network bench To: Ben Dooks , 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: Akira Tsukamoto Message-ID: Date: Tue, 22 Jun 2021 21:05:27 +0900 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/22/2021 5:30 PM, Ben Dooks wrote: > 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? Thanks for the result on the Unmatched with hdparm. Have you tried iperf3? The 15% is high, is it before or with-patch? Akira