Re: [perfmon2] About per-thread monitoring

[Tanima D. <dey...@ya...>]

Hi,
Yes, I have studied that example, and wrote similar code, but for the appThread. But it shows me the same error message for ptrace() while attaching the task. I have given the appThread ID instead of the process ID, and it shows the message:

"cannot attach to threadID, operation is not permitted"

Can you help?
Thanks
Tanima.




________________________________
From: Corey Ashford <cja...@li...>
To: Tanima Dey <dey...@ya...>
Cc: Perfmon <per...@li...>
Sent: Friday, July 17, 2009 6:20:09 PM
Subject: Re: [perfmon2] About per-thread monitoring

On 07/16/2009 04:33 PM, Tanima Dey wrote:
>
> Hi,
>
> Thanks for the reply.
>
> It is mentioned in the manual that the thread to which the context is
> attached is the monitored thread, in my case then it is the application
> thread to which the context should be loaded, right? If it is so, I am
> initializing and loading the context in the appThread, and trying to
> read the counters value in the monitor thread. So I have used ptrace()
> to stop the appThread in the monitor thread and trying to read the
> counters, but it is showing the error message: Cannot attach: Operation
> not permitted. Also I tried to read by saving the file descriptor
> variable, it is also not working.
>
> Must the per-thread monitoring always be self-monitoring? Otherwise, I
> think it will always be the case that the monitoring thread wont have
> any access to PMU state initialized by the appThread.
>
> What wrong I am doing here?Do you have any examples for perthread
> monitoring using threads?
>

You can monitor from the same thread or from another thread, or from 
another thread in a different process.

Have you looked at libpfm/examples_v2.x/task_attach.c ?

It is an example of monitoring events in another task (i.e. process or 
thread).

- Corey