Re: [bpf] af7ec13833: will-it-scale.per_process_ops -2.5% regression

[Yonghong Song]

On 6/28/20 1:50 AM, kernel test robot wrote:
> Greeting,
>
> FYI, we noticed a -2.5% regression of will-it-scale.per_process_ops due to commit:
>
>
> commit: af7ec13833619e17f03aa73a785a2f871da6d66b ("bpf: Add bpf_skc_to_tcp6_sock() helper")
> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master

One of previous emails claims that
    commit: 492e639f0c222784e2e0f121966375f641c61b15 ("bpf: Add 
bpf_seq_printf and bpf_seq_write helpers")
is reponsible for 2.5% improvement for will-it-scale.per_process_ops, 
which I believe is false.

This commit should not cause regression.

Probably the variation of performance is caused by test environment 
which you may want to investigate further to reduce false alarming.
Thanks!

> in testcase: will-it-scale
> on test machine: 192 threads Intel(R) Xeon(R) Platinum 9242 CPU @ 2.30GHz with 192G memory
> with following parameters:
>
> 	nr_task: 16
> 	mode: process
> 	test: mmap1
> 	cpufreq_governor: performance
> 	ucode: 0x5002f01
>
> test-description: Will It Scale takes a testcase and runs it from 1 through to n parallel copies to see if the testcase will scale. It builds both a process and threads based test in order to see any differences between the two.
> test-url: https://github.com/antonblanchard/will-it-scale
>
>
>
> If you fix the issue, kindly add following tag
> Reported-by: kernel test robot <rong.a.chen@xxxxxxxxx>
>
>
> Details are as below:
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