Re: gettimeofday() in hping

Greetings,

Kris Kennaway wrote:
> Stefan Lambrev wrote:
>> Hi,
>>
>> Dag-Erling Sm=C3=B8rgrav wrote:
>>> Stefan Lambrev <[e-mail]> writes:
>>> =20
>>>> I tested all different combination. The performance change is almost=

>>>> invisible (100-200KB/s), and can't be compared with the performance
>>>> boost that TSC gain over ACPI-fast timecounter.  Unfortunately TSC
>>>> doesn't play nice with power saving modes.
>>>>    =20
>>>
>>> This will vary greatly from machine to machine, depending on the exac=
t
>>> hardware and the ACPI BIOS.
>>>
>>> More modern machines have an HPET timer which is supposedly faster th=
an
>>> ACPI yet more reliable than TSC.
>>>
>>> DES
>>>  =20
>> I do not have HEPT on the servers that I test, but simple test on my=20
>> laptop shows
>> that hping can generate with ACPI-fast ~4MB/s traffic, 5MB/s with HPET=

>> and 8MB/s with TSC. I didn't check dummy time counter.
>> Also I noticed that there is a kern.timecounter.tc.XXX.quality (read=20
>> only).
>> Can this be used to reduce quality and speed up performance?
>
> No, they are meaningless values only used to rank the time counters=20
> and choose one at boot.
>
> You should use hwpmc to verify where the application is really=20
> spending time, since gettimeofday doesn't seem to account for it all.
pmc: Unknown Intel CPU.
module_register_init: MOD_LOAD (hwpmc, 0xffffffff8029906d,=20
0xffffffff8054c500) error 78

What was the other way to do this profiling?
Can ktrace help?

Here is sample of kdump -R:

  7501 hping    0.000013 RET   sendto 40/0x28
  7501 hping    0.000019 CALL  sigaction(SIGALRM,0xbfbfe8a8,0xbfbfe890)
  7501 hping    0.000014 RET   sigaction 0
  7501 hping    0.000013 CALL  setitimer(0,0xbfbfe8b4,0xbfbfe8a4)
  7501 hping    0.000016 RET   setitimer 0
  7501 hping    0.000017 CALL  gettimeofday(0xbfbfe870,0)
  7501 hping    0.000022 RET   gettimeofday 0
  7501 hping    0.000015 CALL  gettimeofday(0xbfbfe868,0)
  7501 hping    0.000016 RET   gettimeofday 0
  7501 hping    0.000015 CALL  sendto(0x3,0x28317040,0x28,0,0x8067d80,0x1=
0)
  7501 hping    0.000026 GIO   fd 3 wrote 40 bytes

--=20

Best Wishes,
Stefan Lambrev
ICQ# 24134177


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