On Tue, Jul 07, 2015 at 08:18:08AM -0400, Koehrer Mathias (ETAS/ESW5) wrote: > Hi all, > > we use the RT_PREEMPT kernel fairly long now and it is working really fine. > However, I have one question that is related to measure the available "CPU > headroom" on all available CPU cores. We are using an Intel Core i7 PC > (32 and 64bit, Debian distribution, vanilla kernel + rt_preempt patch). > The question is the same for kernel 3.2.x and 3.18.x. > > On the PC a couple of real time threads are running. They are hard bound > to a particular CPU core (via pthread_setaffinity_np or sched_setaffinity). > As we are using the boot parameter "isolcpus=1-31", all processes run per > default on CPU core 0. Now, I want to measure the total CPU specific load. > How can this be done easily? > > When I use "top" in thread-mode I see the relative CPU load for particular > threads/processes. However the "idle" value in the "top" summary does > not fit. With some experiments I saw the idle value for a CPU core to > be nearly 100% even if on the very same CPU core a real time thread was > consuming about 40% CPU time. I looked into /proc/stat to take the idle > tick value but this value seems not to consider the real time threads. > > > The only approach I found so far is to parse all /proc/PID/stat files > periodically and to extract the fields utime, stime, cutime, cstime, > task_cpu. These values can be used to compute the CPU specific load. > However, the effort to do so is really high. > > Is there any /proc file (or something similar) I can use to get the total > CPU specific load (including real time threads)? Or do I have to enable > a particular kernel configuration to get this value? > > Thanks for any feedback on this question. > > Regards > Mathias I think that if you turn on CONFIG_VIRT_CPU_ACCOUNTING_GEN, you will get per-cpu high resolution idle time accounting as a side effect. (I'm looking at the 3.18 kernel, YMMV for earlier kernels). Regards, Joe -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
