x> same GPU. Right now, it is unclear to me if there is a underlying
Does the stall go away, when you disable dynticks ?
Dynamic ticks are providing a continuous tick long as the machine is
busy. When a core becomes idle, we programm the timer to go off at the
next scheduled timer event, if the event is longer away than the next
tick. When the core goes out of idle (due to the timer or some other
event) we restart the tick.
So you see less timer interrupts (IRQ0 + Local timer interrupts)
Right, that is expected as I explained already. Your desktop does not
use deeper power states. Check /proc/acpi/processor/CPU0/power on both
machines to see the difference. You _cannot_ compare a desktop and a
laptop machine and deduce a regression.
The broadcast mechanism is necessary because the local APIC timer
stops in deeper power states. That's a hardware problem. So if the
core goes into a deeper power state then we arm the broadcast timer
which fires on IRQ0 to wake us up. It is a single timer which is used
by all cores in a system to work around this hardware stupidity. It's
named broadcast because it broadcasts the event to the other cores
when necessary. Your desktop does not use deeper power states,
therefor it does not use the broadcast timer either.
So the timer IRQ0 increasing is neither a Linux BUG nor a regression.
Thanks,
tglx
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