On Tue, 2013-07-30 at 14:41 -0400, Alan Stern wrote: > On Tue, 30 Jul 2013, Steven Rostedt wrote: > > > On Tue, 2013-07-30 at 11:42 -0400, Alan Stern wrote: > > > On Mon, 29 Jul 2013, James Stone wrote: > > > > Just an FYI, it is usually better to email my rostedt@xxxxxxxxxxx > > account. I don't always read my redhat email. That's reserved for > > bugzillas assigned to me ;-) > > I got the address from the top of Documentation/trace/ftrace.txt (which > I was reading at the time to make sure I understood the trace output > correctly). Should that file be updated? > Yes, thanks for letting me know. I used that email a while ago, but I didn't like having Red Hat business mixed in with my upstream work. > > > > # tracer: irqsoff > > > > # > > > > # irqsoff latency trace v1.1.5 on 3.10.0-ver5 > > > > # -------------------------------------------------------------------- > > > > # latency: 2173 us, #4/4, CPU#0 | (M:desktop VP:0, KP:0, SP:0 HP:0 #P:4) > > > > # ----------------- > > > > # | task: apt-check-3628 (uid:1000 nice:19 policy:0 rt_prio:0) > > > > # ----------------- > > > > # => started at: perf_event_update_userpage > > > > # => ended at: retint_careful > > > > # > > > > # > > > > # _------=> CPU# > > > > # / _-----=> irqs-off > > > > # | / _----=> need-resched > > > > # || / _---=> hardirq/softirq > > > > # ||| / _--=> preempt-depth > > > > # |||| / delay > > > > # cmd pid ||||| time | caller > > > > # \ / ||||| \ | / > > > > apt-chec-3628 0d.h. 0us!: local_clock <-perf_event_update_userpage > > > > perf_event_update_userpage should not be taking 2ms to complete. > > How can that be chased down? And even so, 2 ms is a lot smaller than 7 > ms. > > > > This suggests that the IRQ line was disabled or interrupts were > > > disabled on all four CPUs for 7 ms. However, the irqsoff trace shows > > > that the maximum latency was 2 ms. Something strange is going on, but > > > I don't know what or how to find it. > > > > > > Steve, do you have any ideas about this? Or suggestions for other > > > people to ask? > > > > Is there SMIs on this box? Those will not be detected by the latency > > tracers directly. But we do have other tools to detect them. > > What are they, and how can James try them? We have them in the -rt kernel. But they need some work too. Which should get me to push that up on my todo list :-/ -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
