On Fri, Jan 27, 2012 at 03:45:53PM +0000, stephane eranian wrote: > Hi, Hi Stephane, > Ok, with the one-line patch [1], this works much better now. > No more wrap around a 4 billion cycles. Hurrah! Thanks Mans and Ming Lei for helping with this. Unfortunately, I remember Santosh had objections to this patch so that needs to be resolved. > Sampling is okay, though I noticed it tends to not get the > correct number of samples for a controlled run: > > $ perf record -e cycles -c 1009213 noploop 10 > noploop for 10 seconds > > $ perf report -D | tail -20 > cycles stats: > TOTAL events: 9938 > MMAP events: 13 > COMM events: 2 > EXIT events: 2 > THROTTLE events: 12 > UNTHROTTLE events: 12 > SAMPLE events: 9897 > > Should not get throttled samples. Should get abour 10k samples > but only seeing 9897. The max_rate limit is way higher > than what I set the period (1000 samples/sec). But then, > is 3.2.0 throttling is broken. I posted a patch to fix that > yesterday. I will try with my patch applied as well. Ok. Note that on ARM the PMU generates a standard IRQ (i.e. not an NMI) so you may miss samples if they occur during critical kernel sections (and if you look at a profile, spin_unlock_irqrestore will be quite high). A7 and A15 have the ability to filter counters based on privilege level, so you can get more accurate userspace counts there. Will -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
