Re: [LKP] [lkp] [sctp] a6c2f79287: netperf.Throughput_Mbps -37.2% regression

[Xin Long]

> The perf-profile data for the two commits are attached(for the case of
> prsctp_enable=1, the perf-profile data doesn't get collected for the 0
> case for some reason, I'm checking the problem now).
>
> The CPU gets much more idle time in the bisected commit a6c2f79287:
>
>     68.89%     0.70%  [kernel.kallsyms]   [k] entry_SYSCALL_64_fastpath
>     49.32%     0.12%  [kernel.kallsyms]   [k] sys_sendmsg
>     49.17%     0.12%  [kernel.kallsyms]   [k] __sys_sendmsg
>     48.58%     0.22%  [kernel.kallsyms]   [k] ___sys_sendmsg
>     46.69%     0.06%  [kernel.kallsyms]   [k] sock_sendmsg
>     46.31%     0.16%  [kernel.kallsyms]   [k] inet_sendmsg
>     45.90%     0.98%  [kernel.kallsyms]   [k] sctp_sendmsg
>     29.66%     0.45%  [kernel.kallsyms]   [k] sctp_do_sm
>     29.54%     0.23%  [kernel.kallsyms]   [k] cpu_startup_entry
>     28.81%     0.68%  [kernel.kallsyms]   [k] sctp_cmd_interpreter.isra.24
>     26.20%     0.00%  [kernel.kallsyms]   [k] start_secondary
>     23.04%     0.09%  [kernel.kallsyms]   [k] sctp_inq_push
>     23.03%     0.08%  [kernel.kallsyms]   [k] call_cpuidle
>     22.94%     0.00%  [kernel.kallsyms]   [k] cpuidle_enter
>     22.60%     0.18%  [kernel.kallsyms]   [k] cpuidle_enter_state
>     21.99%    21.99%  [kernel.kallsyms]   [k] intel_idle
> ... ...
>
> While its immediate parent commit 826d253d57 is mostly busy working:
>
>     98.53%     0.83%  [kernel.kallsyms]   [k] entry_SYSCALL_64_fastpath
>     78.13%     0.12%  [kernel.kallsyms]   [k] sys_sendmsg
>     78.03%     0.16%  [kernel.kallsyms]   [k] __sys_sendmsg
>     77.08%     0.28%  [kernel.kallsyms]   [k] ___sys_sendmsg
>     74.44%     0.08%  [kernel.kallsyms]   [k] sock_sendmsg
>     73.82%     0.13%  [kernel.kallsyms]   [k] inet_sendmsg
>     73.34%     1.44%  [kernel.kallsyms]   [k] sctp_sendmsg
>     47.52%     0.75%  [kernel.kallsyms]   [k] sctp_do_sm
>     46.19%     0.90%  [kernel.kallsyms]   [k] sctp_cmd_interpreter.isra.24
>     37.17%     1.43%  [kernel.kallsyms]   [k] sctp_outq_flush
>     36.93%     0.08%  [kernel.kallsyms]   [k] sctp_outq_uncork
>     34.24%     0.15%  [kernel.kallsyms]   [k] sctp_inq_push
> ... ...
> No idle related function above 1%.
>
> Will the bisected commit make the idle possible?
No, not at all. :)

pls help to debug as I said in the last reply.