Messages in this thread | | | Subject | Re: [PATCH v2 0/5] riscv: improving uaccess with logs from network bench | From | Ben Dooks <> | Date | Tue, 22 Jun 2021 18:45:37 +0100 |
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On 22/06/2021 13:05, Akira Tsukamoto wrote: > 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?
I will see if there is iperf3 installed. I've not done much other than try booting it and then try booting it with a kernel i've built from upstream.
> The 15% is high, is it before or with-patch?
Can't remember, I did this more to find out if the copy to/from user was going to show up in the times for hdparm.
> Akira >
-- Ben Dooks http://www.codethink.co.uk/ Senior Engineer Codethink - Providing Genius
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