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

[Bernd Petrovitsch]

Hi!

On Tue, 2008-09-16 at 14:50 +0200, Xu Yang 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.

That doesn't make much sense as the same thread can run on a different
CPU after each scheduling decision. And - as it is in userspace -
scheduling can happen before any assembler op.

	Bernd
-- 
Firmix Software GmbH                   http://www.firmix.at/
mobil: +43 664 4416156                 fax: +43 1 7890849-55
          Embedded Linux Development and Services

Re: looking for a function

[Xu Yang]

Hi Bernd,

thanks for you reply.

yes, I know the thread migrates all the time, this is exactly what I
would like to observe. I would like to learn about the thread
migration of some specific scheduling algorithm. so ....

any idea about the function?

Best regards,

Yang

2008/9/16, Bernd Petrovitsch <bernd@firmix.at>:
> Hi!
>
> On Tue, 2008-09-16 at 14:50 +0200, Xu Yang 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.
>
> That doesn't make much sense as the same thread can run on a different
> CPU after each scheduling decision. And - as it is in userspace -
> scheduling can happen before any assembler op.
>
>        Bernd
> --
> Firmix Software GmbH                   http://www.firmix.at/
> mobil: +43 664 4416156                 fax: +43 1 7890849-55
>          Embedded Linux Development and Services
>
>
>

Re: looking for a function

[Arjan van de Ven]

On Tue, 16 Sep 2008 16:11:10 +0200
"Xu Yang" <risingsunxy@googlemail.com> wrote:

> Hi Bernd,
> 
> thanks for you reply.
> 
> yes, I know the thread migrates all the time, this is exactly what I
> would like to observe. I would like to learn about the thread
> migration of some specific scheduling algorithm. so ....
> 
> any idea about the function?

the getcpu() system call will do what you want.



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org

Re: looking for a function

[Xu Yang]

Hi Arjan,

thanks,
I will try that!

Best regards,

Yang

2008/9/16, Arjan van de Ven <arjan@infradead.org>:
> On Tue, 16 Sep 2008 16:11:10 +0200
> "Xu Yang" <risingsunxy@googlemail.com> wrote:
>
> > Hi Bernd,
> >
> > thanks for you reply.
> >
> > yes, I know the thread migrates all the time, this is exactly what I
> > would like to observe. I would like to learn about the thread
> > migration of some specific scheduling algorithm. so ....
> >
> > any idea about the function?
>
> the getcpu() system call will do what you want.
>
>
>
> --
> Arjan van de Ven        Intel Open Source Technology Centre
> For development, discussion and tips for power savings,
> visit http://www.lesswatts.org
>

Re: looking for a function

[Frédéric Weisbecker]

2008/9/16 Xu Yang <risingsunxy@googlemail.com>:
> Hi Bernd,
>
> thanks for you reply.
>
> yes, I know the thread migrates all the time, this is exactly what I
> would like to observe. I would like to learn about the thread
> migration of some specific scheduling algorithm. so ....
>
> any idea about the function?
>

And perhaps you should have a look at the sched_switch tracer which
will log for you the different context switches.

Regards,

Frederic.

Re: looking for a function

[Xu Yang]

Hi Frederic,

thank you very much!
this is very useful for me. :-)

Best regards,

Yang

2008/9/16, Frédéric Weisbecker <fweisbec@gmail.com>:
> 2008/9/16 Xu Yang <risingsunxy@googlemail.com>:
> > Hi Bernd,
> >
> > thanks for you reply.
> >
> > yes, I know the thread migrates all the time, this is exactly what I
> > would like to observe. I would like to learn about the thread
> > migration of some specific scheduling algorithm. so ....
> >
> > any idea about the function?
> >
>
> And perhaps you should have a look at the sched_switch tracer which
> will log for you the different context switches.
>
> Regards,
>
> Frederic.
>

Re: looking for a function

[Chris Snook]

Xu Yang wrote:
> Hi Bernd,
> 
> thanks for you reply.
> 
> yes, I know the thread migrates all the time, this is exactly what I
> would like to observe. I would like to learn about the thread
> migration of some specific scheduling algorithm. so ....
> 
> any idea about the function?
> 
> Best regards,
> 
> Yang

getcpu() should do what you want.

-- Chris

> 2008/9/16, Bernd Petrovitsch <bernd@firmix.at>:
>> Hi!
>>
>> On Tue, 2008-09-16 at 14:50 +0200, Xu Yang 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.
>> That doesn't make much sense as the same thread can run on a different
>> CPU after each scheduling decision. And - as it is in userspace -
>> scheduling can happen before any assembler op.
>>
>>        Bernd
>> --
>> Firmix Software GmbH                   http://www.firmix.at/
>> mobil: +43 664 4416156                 fax: +43 1 7890849-55
>>          Embedded Linux Development and Services
>>
>>
>>
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