Bad power savings with high network traffic

Bad power savings with high network traffic

[Markus Gaugusch]

[I'm not subscribed, please CC: me on answers! Thanks!]
I had my laptop connected to a network with lots of multicast/broadcast
traffic (40kb broadcast + 80kb multicast/sec). The multicast traffic was
only visible on the network meter, when promiscous mode was enabled.

Usually my CPU temperature is around 50°C when being idle, but it raised
up to 54°C! I found out, that although CPU usage was minimal (1-2%), the
C1 state was used very frequently. After unplugging the network cable, the
temperature went down again.

My kernel is 2.4.24 with software suspend patch and realtek 8139 ethernet
card. I suppose, that kernel internal code doesn't honor C-states or
something like that?

Markus

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Re: Bad power savings with high network traffic

[Nate Lawson]

On Sun, 18 Jan 2004, Markus Gaugusch wrote:
> [I'm not subscribed, please CC: me on answers! Thanks!]
> I had my laptop connected to a network with lots of multicast/broadcast
> traffic (40kb broadcast + 80kb multicast/sec). The multicast traffic was
> only visible on the network meter, when promiscous mode was enabled.
>
> Usually my CPU temperature is around 50°C when being idle, but it raised
> up to 54°C! I found out, that although CPU usage was minimal (1-2%), the
> C1 state was used very frequently. After unplugging the network cable, the
> temperature went down again.
>
> My kernel is 2.4.24 with software suspend patch and realtek 8139 ethernet
> card. I suppose, that kernel internal code doesn't honor C-states or
> something like that?

8139 is a piece of junk.  It probably doesn't have hw multicast filter,
hence does a lot of DMA to memory or interrupts and you lose > C1 sleep
states.

-Nate


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