How to get the average/max process scheduling latency

How to get the average/max process scheduling latency

[Teto]

Hi,

I would like to retrieve the average latency between 2 schedulings of
an application. The purpose is to model the service time of the
application (ie. How fast it can empty the TCP buffer).

I could not find an answer yet. I've found that on latest kernel
latency is on average around 3us with a max at 64us (I consider a
moderate load). Is that correct ?

Regards
Matt

How to get the average/max process scheduling latency

[Valdis.Kletnieks at vt.edu]

On Mon, 16 Jun 2014 18:23:56 +0200, Teto said:

> I could not find an answer yet. I've found that on latest kernel
> latency is on average around 3us with a max at 64us (I consider a
> moderate load). Is that correct ?

Depends on your hardware and system load.  I'd hardly expect the same numbers
from a busy Beaglebone or Raspberry Pi as from a idle high-end Intel i7 system....

(And things like processors that drop into sleep states when idle, with
a latency hit to wake up, just add to the confusion....)
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How to get the average/max process scheduling latency

[Teto]

Thanks for the answer.

Do you know any tool/software to retrieve the average latency for a
specific program on a specific platform. This is to modelize the
application rate for data processing.



2014-06-19 22:16 GMT+02:00  <Valdis.Kletnieks@vt.edu>:
> On Mon, 16 Jun 2014 18:23:56 +0200, Teto said:
>
>> I could not find an answer yet. I've found that on latest kernel
>> latency is on average around 3us with a max at 64us (I consider a
>> moderate load). Is that correct ?
>
> Depends on your hardware and system load.  I'd hardly expect the same numbers
> from a busy Beaglebone or Raspberry Pi as from a idle high-end Intel i7 system....
>
> (And things like processors that drop into sleep states when idle, with
> a latency hit to wake up, just add to the confusion....)

How to get the average/max process scheduling latency

[Valdis.Kletnieks at vt.edu]

On Fri, 20 Jun 2014 15:36:47 +0200, Teto said:
> Do you know any tool/software to retrieve the average latency for a
> specific program on a specific platform. This is to modelize the
> application rate for data processing.

You need to add "while running under a specific application load", because
latencies can be different if you're under high enough load to keep the CPU
running at high clock rate, versus if it's dropping to a low clock rate and
then into a sleep state....

The 'latencytop' utility may help here.

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