[added Pawel, author of the patches]
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.
David
Hello,
thank you David! Those patches are great! I decided to access perf
clock through clock_gettime because I'm more used to this call since I
used it before.
My long term preference as well with a hook into vdso page.
I understand that the patches are a bit hardcoded, right? I tried to
#include "/usr/include/linux/time.h" after #include <time.h> but they
seem to conflict. If I just extract the interesting bits (#define
CLOCK_PERF) it seems to work. Is there a cleaner way to use this right now?
They should just work. I seem to have misplaced my test case; I don't
recall having problems with it.
JFTR, I have written a very small app that demonstrate the usage of
this clock_gettime + perf (attached). It is very interesting to see that
the difference between the monotonic and the perf clock is rather
similar. However, as time goes by, at least in my machine, perf clock
seems to advance at a faster pace than the monotonic clock.
that's why we would like to get a perf_clock/trace_clock time source
exported by the kernel.
David
--
To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
