Alexey Kuznetsov wrote:
I want to stress that this is a small desktop-only system without any complex
routing setup,
thus 20 wakeups / seconds seems extreme overkill / bug.
Yes, I saw this too when powertop was announced and I played with it
for a while. I worried about this until I found out that this does not
affect power consumption at all. At least I found no correlation. :-)
the effect on power consumption depends on 2 things
1) cpu type
2) other wakeups
depending on the cpu type, there is a point of diminishing returns in
power saving between approximately 15 msec and 45 msec of being in a
deep C-state. If you have a 20/sec timer, that alone will not be of
big impact, and if you have a cpu of the "15 msec" type, there's quite
some headroom even.
the other thing is other wakeups: if this timer is 20, and another is
another 20, and yet another is another 20, soon you'll be in the area
where it hurts power. Yet no single timer is "at fault", it's the
cumulative effect that hurts.
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