PERF PARAMETERS

PERF PARAMETERS

[Jessica Foest]

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Hi

i tried to retrieve system calls traces with all perf context parameters .
the problem is that only a few PERF counters are activated and lttng fails
to activate  the other perf context parameters.
how can i solve it ?

regards

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Re: PERF PARAMETERS

[Jessica Foest]

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Thanks :)


2014-08-27 13:30 GMT-04:00 Julien Desfossez <jdesfossez@efficios.com>:

> Hi,
>
> On 14-08-26 11:21 PM, Jessica Foest wrote:
> > Hi
> >
> > i tried to retrieve system calls traces with all perf context parameters
> > . the problem is that only a few PERF counters are activated and lttng
> > fails to activate  the other perf context parameters.
> > how can i solve it ?
>
> There is a hardware limit on the number perf PMU counters that can be
> activated at the same time. It depends on the CPU and if you are on a
> virtual machine.
> If I remember correctly it is 3 or 4 on the i7.
>
> Julien
>

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Re: PERF PARAMETERS

[Julien Desfossez]

Hi,

On 14-08-26 11:21 PM, Jessica Foest wrote:
> Hi 
> 
> i tried to retrieve system calls traces with all perf context parameters
> . the problem is that only a few PERF counters are activated and lttng
> fails to activate  the other perf context parameters.
> how can i solve it ?

There is a hardware limit on the number perf PMU counters that can be
activated at the same time. It depends on the CPU and if you are on a
virtual machine.
If I remember correctly it is 3 or 4 on the i7.

Julien

Re: PERF PARAMETERS

[Jonathan Rajotte-Julien]

Hi Jessica,

When you say " lttng fails to activate" is it on the lttng add-context command or after looking at the trace ?

Can you give us the output from "lttng version"?

If possible can you send the complete sequence of action?

Thanks

On 08/26/2014 11:21 PM, Jessica Foest wrote:
> Hi 
> 
> i tried to retrieve system calls traces with all perf context parameters . the problem is that only a few PERF counters are activated and lttng fails to activate  the other perf context parameters.
> how can i solve it ?
> 
> regards 
> 
> 
> _______________________________________________
> lttng-dev mailing list
> lttng-dev@lists.lttng.org
> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>