Re: [RFC] perf: need to expose sched_clock to correlate user sampleswith kernel samples
From: David Ahern
Date: Sun Mar 31 2013 - 12:24:05 EST
On 3/14/13 1:57 PM, Pawel Moll wrote:
Ok, how about the code below? I must say I have some doubts about the
resolution, as there seem to be no generic way of figuring it out for
the sched_clock (the arch/arm/kernel/sched_clock.c is actually
calculating it, but than just prints it out and nothing more).
And, to summarize, we went through 3 ideas:
1. ioctl() - http://article.gmane.org/gmane.linux.kernel/1433933
2. syscall - http://article.gmane.org/gmane.linux.kernel/1437057
3. POSIX clock - below
John also suggested that maybe the perf could use CLOCK_MONOTONIC_RAW
instead of local/sched_clock().
Any chance a decision can be reached in time for 3.10? Seems like the
simplest option is the perf event based ioctl.
Converting/correlating perf_clock timestamps to time-of-day is a feature
I have been trying to get into perf for over 2 years. This is a big
piece needed for that goal -- along with the xtime tracepoints:
https://lkml.org/lkml/2013/3/19/433
David
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