On 2024/9/10 0:54, Mina Almasry wrote: > On Mon, Sep 9, 2024 at 4:21 AM Yunsheng Lin <linyunsheng@xxxxxxxxxx> wrote: >> >> On 2024/9/9 13:43, Mina Almasry wrote: >> >>> >>> Perf - page-pool benchmark: >>> --------------------------- >>> >>> bench_page_pool_simple.ko tests with and without these changes: >>> https://pastebin.com/raw/ncHDwAbn >>> >>> AFAIK the number that really matters in the perf tests is the >>> 'tasklet_page_pool01_fast_path Per elem'. This one measures at about 8 >>> cycles without the changes but there is some 1 cycle noise in some >>> results. >>> >>> With the patches this regresses to 9 cycles with the changes but there >>> is 1 cycle noise occasionally running this test repeatedly. >>> >>> Lastly I tried disable the static_branch_unlikely() in >>> netmem_is_net_iov() check. To my surprise disabling the >>> static_branch_unlikely() check reduces the fast path back to 8 cycles, >>> but the 1 cycle noise remains. >> >> Sorry for the late report, as I was adding a testing page_pool ko basing >> on [1] to avoid introducing performance regression when fixing the bug in >> [2]. >> I used it to test the performance impact of devmem patchset for page_pool >> too, it seems there might be some noticable performance impact quite stably >> for the below testcases, about 5%~16% performance degradation as below in >> the arm64 system: >> > > Correct me if I'm wrong here, but on the surface here it seems that > you're re-reporting a known issue. Consensus seems to be that it's a > non-issue. > > In v6 I reported that the bench_page_pool_simple.ko test reports a 1 > cycle regression with these patches, from 8->9 cycles. That is roughly > consistent with the 5-15% you're reporting.
