On 2015-10-31 at 10:28 "'Davide Libenzi' via Akaros" <[email protected]> wrote: > But the timers have no use alone. There is nothing that uses them, if > the profiler is not running.
The separation between the timer and the start/stop was done intentionally. Here's the rationale from when that code was written: commit 383648aa099a3974b397cf81d1a82969bf7814fc Author: Barret Rhoden <[email protected]> Date: Tue Dec 9 22:44:37 2014 -0800 Per-cpu timer control for oprofile sampling To use oprof now, you need to set the timer, then enable the profiling. If/when we add other tracers that can be turned on and off, we'll continue to use this model: set the collection of things to trace, then start them all at once. If you don't have the timers turned on, but you run opstart, other traces, such as TRACE_ME and whatnot (like perhaps writing traces from userspace via kpoprofile) will still be collected. I don't have a control for various TRACE_MEs yet. Maybe we can add one (like printx). Some examples: To turn on the timer on core 0. This turns on an alarm/IRQ: $ echo optimer 0 on > /prof/kpctl Then start the actual profiling/collection: $ echo opstart > /prof/kpctl To stop collecting: $ echo opstop > /prof/kpctl To turn off all the timers: $ echo optimer all off > /prof/kpctl Oh, and you can adjust the timer period if you like. Default is 1ms. $ echo optimer period 1000 > /prof/kpctl (period is in usec) -- You received this message because you are subscribed to the Google Groups "Akaros" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. For more options, visit https://groups.google.com/d/optout.
