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    SubjectRe: [patch] i386 dynamic ticks 2.6.13-rc4 (code reordered)
    On Sun, 7 Aug 2005 00:54, Theodore Ts'o wrote:
    > On Tue, Aug 02, 2005 at 02:43:55PM +1000, Con Kolivas wrote:
    > > This is a code reordered version of the dynamic ticks patch from Tony
    > > Lindgen and Tuukka Tikkanen - sorry about spamming your mail boxes with
    > > this, but thanks for the code. There is significant renewed interest by
    > > the lkml audience for such a feature which is why I'm butchering your
    > > code (sorry again if you don't like me doing this). The only real
    > > difference between your code and this patch is moving the #ifdef'd code
    > > out of code paths and putting it into dyn-tick specific files.
    > >
    > > This has slightly more build fixes than the last one I posted and boots
    > > and runs fine on my laptop. So far at absolute idle it appears this
    > > pentiumM 1.7 is claiming to have _25%_ more battery life. I'll need to
    > > investigate further to see the real power savings.
    > Hi Con,
    > I had a chance to try out your patch (2.6.13-rc4-dtck-2.patch) and
    > using either the APIC or PIT timer, if dynamic tick is enabled, on my
    > laptop, this kicks up the bus mastering activity enough so that the
    > processor doesn't have a chance to enter the C4 state, and stays stuck
    > at C2. As a result, enabling dynamic tick _increases_ power
    > consumption by 20% on my T40 laptop (1.6 MHz Pentium M).

    Lovely! (not)

    > I monitored
    > power utilization using pmstats-0.2, and used
    > /proc/acpi/processor/CPU/power to monitor bus mastering activity and the
    > CPU C-states.
    > As soon as I disabled dynamic tick using:
    > echo 0 > /sys/devices/system/timer/timer0/dyn_tick_state
    > The number of ticks went up to 1024, bus mastering activity dropped to
    > zero, and the processor entered C4 state, and power utilization
    > dropped by 20%.
    > When I enabled dynamic tick using:
    > echo 1 > /sys/devices/system/timer/timer0/dyn_tick_state
    > The number of ticks dropped down to 60-70 HZ, bus mastering activity
    > jumpped up to being almost always active,

    Anyone know why this would happen?

    > and the processor stayed
    > stuck at C2 state, and power utilization climbed back up by 20%.
    > This was on a completely idle, freshly booted machine, without X
    > running and just a console login.

    Thanks for testing.

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