On Monday, August 05, 2013 12:40:13 PM Viresh Kumar wrote: > Please remember adding cc'd lists/people in your next mail > > On Sat, Aug 3, 2013 at 1:15 AM, Guru Prasad <gurupras@xxxxxxxxxxx> wrote: > > I was recently running some SPEC benchmarks to test the way in which > > cpufreq module adjusts the CPU frequency for various benchmarks and I > > noticed that cpufreq always tends to rest at the maximum frequency > > regardless of the benchmark on ondemand / conservative. > > They will stay there if cpu is busy doing some activity.. > > > I then tried to identify memory intensive benchmarks > > (http://users.elis.ugent.be/~leeckhou/papers/isca12-2.pdf) and upon > > running milc / libquantum, I noticed that the same trend continued. > > > > Does this mean that memory operation latencies are attributed as CPU busy time? > > Could someone explain the inner workings behind this? What does the > > CPU *really* do while the load/store is executing? Is it busy-waiting > > / idle? > > We actually take cpu's busy vs idle time for all calculations here.. > idle time is calculated by the time cpu was running its idle thread.. > i.e. when CPU doesn't have any process to run and is idle.. > > But in your case not sure how cpu would behave.. If cpu is doing > word-by-word copy of some stuff, it would be busy most of the > time and isn't really running its idle thread. And so would be counted > as busy I suppose.. > > But if some DMA is taking care of copying stuff then it can be idle, > depending on what else is getting scheduled on it. > > @Rafael: Am I right? All depends on whether or not the CPU is idle from the scheduler viewpoint, so basically this is correct. Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
