On Sat, 2008-08-02 at 18:21 +0100, Samuel Thibault wrote: > Anthony Liguori, le Sat 02 Aug 2008 09:46:30 -0500, a écrit : > > Samuel Thibault wrote: > > >Beth Kon, le Sat 02 Aug 2008 06:05:14 -0500, a écrit : > > > > > >>I was trying to reproduce the wakeup every 10ms that > > >>Samuel Thibault mentioned, thinking the HPET would improve it. > > >>But for an idle guest in both cases (with and without HPET), the > > >>number of wakeups per second was relatively low (28). > > >> > > > > > >I was referring to vl.c's timeout = 10; which makes the select call > > >use a timeout of 10ms. That said, "/* If all cpus are halted then wait > > >until the next IRQ */", so maybe that's why you get slower wakeups per > > >second. I'm still surprised because of the call to qemu_mod_timer in > > >pit_irq_timer_update which should setup at least a 100Hz timer with > > >linux guests (when they don't have HPET available). > > > > > > > The patch disables that when hpet is active. > > That's why I would expect, indeed, but he is reporting that _without_ > HPET he gets low wakeups per second already. > > Samuel
Yes, 28 is incorrect. I was misinterpreting the output of powertop, shown here: Wakeups-from-idle per second : 27.7 interval: 10.0s no ACPI power usage estimate available Top causes for wakeups: 46.1% ( 63.9) qemu-system-x86 : schedule_timeout (process_timeout) 36.5% ( 50.6) qemu-system-x86 : sys_timer_settime (posix_timer_fn) ... The "Wakeups-from-idle per second" reports 27.7, but the powertop source code shows that this value is the total wakeups-per-second divided by the number of online processors. So the proper number of wakeups-per-second caused by the select is 63.9, which makes more sense. Looking at the main_loop code, there is no way to get a timeout of greater than 10 without setting icount. > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to [EMAIL PROTECTED] > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Elizabeth Kon (Beth) IBM Linux Technology Center Open Hypervisor Team email: [EMAIL PROTECTED] -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
