On Thu, Jun 6, 2013 at 8:01 AM, David Ahern <dsah...@gmail.com> wrote: > > It's a VM and not running on KVM so there is no PMU which means the -e > cycles is most likely falling back to -e cpu-clock. You should see this in a > message with the -v flag on record. perf-script should dump out the events > and show cpu-clock versus cycles. > > Based on that I suggest trying -e cpu-clock on your original host. If that > works then something is messed up with the pmu config on the host.
Thanks. It wasn't clear to me if a VM had the same access to the PMU that a non-virtualized host would. But I guess that might explain why a bunch of events I'd expect samples for didn't have any (ex: iTLB-load-misses), even on the VM that did record some samples? I re-ran the record on the VM with -v and did see the message about falling back to cpu-clock-ticks, but only after I added the cycles even to my events list. Which actually leads into a question regarding event sampling. The documentation I have found mentions a "default sampling event" (cycles) but doesn't explain the concept of a sampling event in detail. Does each event listed with -e have its own sample period/rate that can be adjusted? Or do -c or -F apply to all events sampled? Even I don't sample cycles, is the default sampling rate still 1000Hz for all events sampled in the absence of -c or -F? Regarding using -e cpu-clock on the original host, that doesn't appear to have changed the perf record behavior. Neither does using -e cycles. And even with -v on record, I didn't see any additional messaging (like fall back to cpu-clock). But I do still get sample data if I run with -a. *shrug*. Not a big deal at this point - running perf on this particular host/OS might not be something I need to do, so for now I can drop it. But if you or anyone else is interested in continuing to troubleshoot it, I'd be glad to assist. Andy > > David > >> >> So...Ubuntu thing? Or maybe just a 10.04 thing (yeah, I know it's old). >> >> Maybe this'll help someone. >> >> Thanks all. >> Andy >> > -- 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
