> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of > Vaidyanathan Srinivasan > Sent: 2008年3月31日 14:35 > To: Arjan van de Ven > Cc: [email protected] > Subject: Re: [Discuss] How does powertop get the wake-up rate? > > * Arjan van de Ven <[EMAIL PROTECTED]> [2008-03-28 12:56:13]: > > > Vaidyanathan Srinivasan wrote: > >> Hi Arjan, > >> > >> I have been using powertop to find wakeup events and try > to correlate > >> with total interrupts received by the idle system. I want > to see the > >> rate of local timer interrupts go down as we optimise the > drivers and > >> user-space applications to avoid polling. > >> > >> I observed that powertop shows very low wake-from-idle rate on SMP > >> system and the wake-from-idle rate is very high when all > other CPUs are > >> offlined and only CPU0 is operational. I have routed all > irqs to CPUs > >> before the experiment. > > > > powertop shows wakeups *per cpu* ... > > Ok, so the wakeups are averaged out? Total wake-ups divided by current > number of CPUs? >
Yes. If you read the code, you will see that 'wakeups_per_second' is divided by sysconf(_SC_NPROCESSORS_ONLN). > Another related question is how is wake *from idle* computed, how is > the wakeup of non-idle CPUs and idle CPUs distinguished? > 'Wakeups-from-idle per second' is computed by taking advantage of the timer_stats facility in kernel. _______________________________________________ Discuss mailing list [email protected] http://mail.lesswatts.org/mailman/listinfo/discuss
