On 31/10/13 17:48, Andi Kleen wrote:
In fact, I expected that for each entry into the PEBS a handler
would be executed, but Intel documentations points that to use PEBS
the tool (here perf) needs to allocate space for multiple PEBS
entries, so the when the handler is invoked there may be multiple
entries in the buffer, which makes things a little more obscure.
perf always uses threshold 1 for the PEBS buffer.
But yes there is some delay until the handler executes, and the
time stamp is only computed in the handler.
David, Andi,
thank you for your valuable comments, they're really helpful.
David, wrt to the clock, which actually calls local_clock() I'm a bit
worried about the comment in sched/clock.c
* Similar to cpu_clock() for the current cpu. Time will only be observed
* to be monotonic if care is taken to only compare timestampt taken on the
* same CPU.
I'll rerun my experiments making sure that I pin the processes to a
single CPU.
Again, thank you!
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