looking for a function

looking for a function

[Xu Yang]

Hi guys,

I am looking for a function that can show me the current thread is
running on which cpu.

e.g I am using pthread to write a multithreaded program, in each
thread I would like to insert such kind of function so that I can know
on which cpu this thread is running on.

which function should be used?

thanks for the help!!

best regards,



Yang

Re: looking for a function

[Steve Graegert]

Xu Yang,

On Linux sched_getcpu(3) comes to mind.  This function is not
particularly useful since the information returned by the function
might not be correct at the point of its return as threads can be
switched to other CPUs (read: cores) at anytime (although CPU/core
switching can be quite expensive due to cache line bouncing for
instance)

So, once the information has been obtained it might already be
obsolete.  Anyway, I hope that is what you're looking for.

        \Steve

--

Steve Grägert


On Tue, Sep 16, 2008 at 3:26 PM, Xu Yang <risingsunxy@googlemail.com> wrote:
>
> Hi guys,
>
> I am looking for a function that can show me the current thread is
> running on which cpu.
>
> e.g I am using pthread to write a multithreaded program, in each
> thread I would like to insert such kind of function so that I can know
> on which cpu this thread is running on.
>
> which function should be used?
>
> thanks for the help!!
>
> best regards,
>
>
>
> Yang
> --
> To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in
> the body of a message to majordomo@vger.kernel.org
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Re: looking for a function

[Xu Yang]

Hi Steve,

thanks for your reply :-)

I will try this. I am evaluating some scheduling algorithm, so I would
like to learn about how the threads migrate. That is why I am asking
for such kind of function.

thank for your help!

Bes regards,

Yang

2008/9/16, Steve Graegert <graegerts@gmail.com>:
> Xu Yang,
>
> On Linux sched_getcpu(3) comes to mind.  This function is not particularly
> useful since the information returned by the function might not be correct
> at the point of its return as threads can be switched to other CPUs (read:
> cores) at anytime (although CPU/core switching can be quite expensive due to
> cache line bouncing for instance)
>
> So, once the information has been obtained it might already be obsolete.
> Anyway, I hope that is what you're looking for.
>
>         \Steve
>
> --
>
> Steve Grägert
>
>
>
> On Tue, Sep 16, 2008 at 3:26 PM, Xu Yang <risingsunxy@googlemail.com> wrote:
> >
> > Hi guys,
> >
> > I am looking for a function that can show me the current thread is
> > running on which cpu.
> >
> > e.g I am using pthread to write a multithreaded program, in each
> > thread I would like to insert such kind of function so that I can know
> > on which cpu this thread is running on.
> >
> > which function should be used?
> >
> > thanks for the help!!
> >
> > best regards,
> >
> >
> >
> > Yang
> > --
> > To unsubscribe from this list: send the line "unsubscribe
> linux-c-programming" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at
> http://vger.kernel.org/majordomo-info.html
> >
>
>
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