Re: Information regarding the perf tool

[Harald Servat <harald.servat@bsc.es>]

On 12/12/13 01:56, David Ahern wrote:
> On 11/4/13, 10:26 AM, Harald Servat wrote:
>> On 31/10/13 19:22, David Ahern wrote:
>>> On 10/31/13, 11:23 AM, Harald Servat wrote:
>>>> Which is the relation between perf_clock() (or local_clock()) and
>>>> clock_gettime (CLOCK_MONOTONIC, ). Are they the same? If not, is
>>>> there a
>>>> way to correlate them? Or alternatively, is it possible to call
>>>> local_clock() from the userland?
>>>
>>> We still do not have a means of correlating perf_clock to time-of-day,
>>> monotonic or any other clock source. Still trying.
>>>
>>> Pawell Moll has a couple of patches posted -- one uses an ioctl to get
>>> perf_clock timestamps the other makes perf_clock accessible through
>>> clock_gettime. See attached.
>>>
>
> Coming back to this....
>
> Here is a module version of the posix clock approach:
>   https://github.com/dsahern/linux/blob/perf-full-monty/README.ahern
>
> As far as I can tell it works for 2.6.38 and forward and there should
> not be a conflict with the CLOCK_PERF id of 12. No need to patch and
> build your kernel, just build the module, load and go.
>
> That branch also has time-of-day hooks for record, report, script and
> sched.
>

Thank you very much David. Using a module instead of recompiling would 
be a very nice alternative. I'll give it a try.

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