Messages in this thread |  | | | Date | Mon, 30 May 2011 18:41:34 -0600 | | From | David Ahern <> | | Subject | Re: perf: h/w counters not counted and no error/info reported to user |
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On 05/30/2011 03:04 PM, Ashwin Chaugule wrote: > Hi David, > > On Fri, May 27, 2011 at 12:36 PM, David Ahern <dsahern@gmail.com> wrote: >> >> Ok, I got it now. On some occasions for simple programs -- like sleep 1 >> -- the counter reads show: >> >> cycles: 0 1066485 0 >> >> While the counter value is non-0, the time enabled and running values >> are 0 and those latter two are used by stat to say "not-counted". > > I've seen time-enabled = 0 too, but I suspected that's because on my > kernel the sched_clock implementation was missing. (defaults to a > jiffies based timer)
I think in the case of 'perf stat -- sleep 1' it runs so quickly that sometimes it does not cross timer ticks and the time_enabled comes out 0.
> I saw your patch for initializing the fd's to -1's, but I'm unable to > see how that makes the value of time-enabled non zero ?
It doesn't. That patch addresses unsupported counters in the default list (e.g., -ddd on a T9550 Core2Duo). The first open fails (cpu 0, thread 0) and the entire FD array is not reset to -1 (from its initialization to 0).
David
> > Cheers, > Ashwin
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