Re: Help with analysing JIT perf report

I've clicked 'a' on this erts_schedule and see following:


Percent│        mov    erts_msacc_enabled,%eax
       │        movq   $0x0,0x20(%rsp)
       │        test   %eax,%eax
       │      ↓ je     7e3
       │        mov    erts_msacc_key,%edi
       │      → callq  ethr_tsd_get
       │        mov    %rax,0x20(%rsp)
       │ 7e3:   test   %ebx,%ebx
       │        movl   $0x1,0x18(%rsp)
       │      ↓ jne    1702
       │ 7f3:   mov    0xb0(%r14),%eax
       │        test   %eax,%eax
       │      ↓ je     1660
       │        movabs $0x7fffffffffffffff,%r13
       │        xor    %ebx,%ebx
       │ 80e:   mov    $0x64,%edx
       │      ↓ jmp    826
  4.73 │ 815:   subl   $0x1,0x2c(%rsp)
  1.64 │        mov    0x2c(%rsp),%eax
  1.31 │     ┌──test   %eax,%eax
       │     ├──jle    15a0
  0.03 │ 826:│  mov    0x18(%rbp),%r12d
  0.01 │     │  mov    %r12d,%eax
       │     │  and    $0x9,%eax
  0.67 │     │  cmp    $0x9,%eax
       │     │↓ jne    15a0
 86.62 │     │  pause
  0.06 │     │  sub    $0x1,%edx
  3.92 │     │↑ jne    815
  0.16 │     │→ callq  sched_yield@plt
  0.00 │     │  test   %eax,%eax
       │     │  mov    $0x64,%edx




82% on some instruction pause

I will try to run this again on non-lcnt beam, but seems that this is
somewhere around spinlock?

On Wed, Jun 23, 2021 at 11:39 AM Max Lapshin <[email protected]> wrote:
>
> Perf report shows me things that I cannot analyse:
>
>
> +   63.85%    51.25%  streamer  beam.lcnt.smp           [.] erts_schedule
> +   59.99%     0.02%  streamer  beam.lcnt.smp           [.]
> erts_dirty_process_main
> +   29.50%     0.04%  streamer  jitted-881027-8664.so   [.]
> gen_server:handle_msg/6
> +   25.66%     0.04%  streamer  jitted-881027-34178.so  [.]
> mpts_reader:handle_info/2
>
>
> mpts_reader is my code and thanks for pointing out to me that it seems
> to be the CPU eater.
>
> I cannot understand what means that erts_schedule takes 63 / 51% of time.
> Is erts_schedule a container to all functions below?