Hi Joe, > > 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 the x86 (32bit) does not support HAVE_VIRT_CPU_ACCOUNTING_GEN. Only the 64bit version does... And I need an approach that works for 32 and 64 bit x86. In the meantime I have found a patch from Carsten Emde that is used on the OSADL QA farm: https://www.osadl.org/monitoring/patches/r5s1/sched-add-per-cpu-load-measurement.patch This patch does exactly what I need... One minor note on this patch: There is an issue with writing to /proc/idleruntime/resetall. The following patch fixes that... Index: linux-3.18.13-rt10/kernel/sched/cpu_idleruntime.c =================================================================== --- linux-3.18.13-rt10.orig/kernel/sched/cpu_idleruntime.c +++ linux-3.18.13-rt10/kernel/sched/cpu_idleruntime.c @@ -82,7 +82,6 @@ static ssize_t idleruntime_resetall(stru static const struct file_operations idleruntime_resetall_fops = { .write = idleruntime_resetall, - .release = single_release, }; static int idleruntime_open(struct inode *inode, struct file *file) Regards Mathias -- 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
