pthread_getcpuclockid() and clock_gettime() with Xenomai pthread

pthread_getcpuclockid() and clock_gettime() with Xenomai pthread

[Rajesh Venkataraman]

Hi,
   For the linux pthreads we have used pthread_getcpuclockid() to get the
threads cpu time clock. Then periodically we do a clock_gettime() on this
timer to get all threads run time. Then do clock_gettime( CLOCK_MONOTONIC,
&ts ) to get the total system. Using the individual thread run time and
total run time, we calculate the percentage of CPU utilization for each
thread. Now we have moved the realtime thread to xenomai user space.
The clock_gettime() on a xenomai user thread returns an error.   How do we
calculate what percentage of the CPU is utilized by the xenomai thread in
our Application?

  We also get the idle time of the CPU from the /proc/stat and calculate
the reserve percentage based on the total system time. Does linux idle time
also include xenomai run time?

  Is this correct method for calculating the CPU utilization percentage per
thread in a system/application with xenomai and linux pthreads running in a
single process?

Rajesh

Re: pthread_getcpuclockid() and clock_gettime() with Xenomai pthread

[Jan Kiszka]

On 27.08.21 03:15, Rajesh Venkataraman via Xenomai wrote:
> Hi,
>    For the linux pthreads we have used pthread_getcpuclockid() to get the
> threads cpu time clock. Then periodically we do a clock_gettime() on this
> timer to get all threads run time. Then do clock_gettime( CLOCK_MONOTONIC,
> &ts ) to get the total system. Using the individual thread run time and
> total run time, we calculate the percentage of CPU utilization for each
> thread. Now we have moved the realtime thread to xenomai user space.
> The clock_gettime() on a xenomai user thread returns an error.   How do we
> calculate what percentage of the CPU is utilized by the xenomai thread in
> our Application?
> 
>   We also get the idle time of the CPU from the /proc/stat and calculate
> the reserve percentage based on the total system time. Does linux idle time
> also include xenomai run time?
> 
>   Is this correct method for calculating the CPU utilization percentage per
> thread in a system/application with xenomai and linux pthreads running in a
> single process?
> 

Xenomai does not support pthread_getcpuclockid for reading the consumed
time of a thread. There are stats under /proc/xenomai/sched/acct, rtps
uses them, but reading those require switching to Linux (if that is an
issue for your use case). And there is an internal cobalt_thread_stat()
syscall already, used only by some non-posix skins so far.

I'm sitting on non-upstream changes to export the CPU usage of thread to
userland without leaving RT, actually even without issuing a syscall.
But those need rework in order to attach to some posix interface.

What are your requirements on a statistic interface? Who is going to
monitor who, and under which constraints?

Jan

-- 
Siemens AG, T RDA IOT
Corporate Competence Center Embedded Linux

Re: pthread_getcpuclockid() and clock_gettime() with Xenomai pthread

[Rajesh Venkataraman]

Hi Jan,
   We are currently getting the total system time and all linux pthread run
time using the clock_gettime(). Then we are getting the linux idle time
from /proc/stat. We are getting the xenomai thread times and total xenomai
time from /proc/xenomai/sched/acct. Subtract the total xenomai time from
linux ide. Then calculate as a percentage individual thread CPU utilization
and reserve percentage. We can do this in a Linux thread, but it would be
nice if we had a single interface/api for getting the per thread CPU
utilization for the whole system(Linux and Xenomai).

Rajesh


On Fri, Aug 27, 2021 at 5:40 AM Jan Kiszka <jan.kiszka@siemens.com> wrote:

> On 27.08.21 03:15, Rajesh Venkataraman via Xenomai wrote:
> > Hi,
> >    For the linux pthreads we have used pthread_getcpuclockid() to get the
> > threads cpu time clock. Then periodically we do a clock_gettime() on this
> > timer to get all threads run time. Then do clock_gettime(
> CLOCK_MONOTONIC,
> > &ts ) to get the total system. Using the individual thread run time and
> > total run time, we calculate the percentage of CPU utilization for each
> > thread. Now we have moved the realtime thread to xenomai user space.
> > The clock_gettime() on a xenomai user thread returns an error.   How do
> we
> > calculate what percentage of the CPU is utilized by the xenomai thread in
> > our Application?
> >
> >   We also get the idle time of the CPU from the /proc/stat and calculate
> > the reserve percentage based on the total system time. Does linux idle
> time
> > also include xenomai run time?
> >
> >   Is this correct method for calculating the CPU utilization percentage
> per
> > thread in a system/application with xenomai and linux pthreads running
> in a
> > single process?
> >
>
> Xenomai does not support pthread_getcpuclockid for reading the consumed
> time of a thread. There are stats under /proc/xenomai/sched/acct, rtps
> uses them, but reading those require switching to Linux (if that is an
> issue for your use case). And there is an internal cobalt_thread_stat()
> syscall already, used only by some non-posix skins so far.
>
> I'm sitting on non-upstream changes to export the CPU usage of thread to
> userland without leaving RT, actually even without issuing a syscall.
> But those need rework in order to attach to some posix interface.
>
> What are your requirements on a statistic interface? Who is going to
> monitor who, and under which constraints?
>
> Jan
>
> --
> Siemens AG, T RDA IOT
> Corporate Competence Center Embedded Linux
>