Messages in this thread | | | Date | Fri, 26 Feb 2010 12:20:08 +0100 | From | Mikael Pettersson <> | Subject | Re: Dynticks on Vortex86SX ? (Cx486SLC + just the standard i8254 PC timer) |
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Frantisek Rysanek writes: > Dear Gentlemen, > > I'm having fun with a Vortex-based motherboard, under 2.6.33. > Linux reports the CPU as a Cx486SLC :-) > A complete PC-compatible motherboard (without VGA) running at ~ 2 > Watts. > I'm wondering how to decrease the power consumption even further, > and "tickless" operation comes to mind. > And that's where I have a problem. Even if I enable > "Tickless System (Dynamic Ticks)" in the menuconfig, > there's no apparent change in consumption, and I still get > around 200-300 timer interrupts per second... > > These are some entries from my .config that might be relevant: > > CONFIG_TICK_ONESHOT=y > CONFIG_NO_HZ=y > # CONFIG_HIGH_RES_TIMERS is not set > CONFIG_M486=y > CONFIG_HZ_250=y > CONFIG_HZ=250
Select HZ=100.
> The only timer that this platform contains (known to Linux) > is the generic i8254-compatible PC timer. > > Makes me wonder if this platform is capable of "tickless" operation > at all. Or maybe my particular combination of features in the .config > effectively prevents the long idle periods from occurring? > > Apart from a standard init and getty's, there's a dhclient and sshd > running on the machine... it's a fairly minimal text-mode system. > > Any ideas are welcome :-)
Enable CONFIG_DEBUG_KERNEL and CONFIG_TIMER_STATS, rebuild and reboot. cat /proc/interrupts, echo 1 > /proc/timer_stats, sleep for 10 seconds, cat /proc/timer_stats and /proc/interrupts. That'll tell you which timers are firing the most, which translates into requiring frequent timer interrupts.
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