Mark Gross wrote: > On Tue, Oct 09, 2007 at 11:41:17AM -0700, Kok, Auke wrote: >> Lennart Sorensen wrote: >>> On Mon, Oct 08, 2007 at 03:31:51PM -0700, Kok, Auke wrote: >>>> you most certainly want to do this in userspace I think. >>>> >>>> One of the biggest problems is that link negotiation can take a >>>> significant amount >>>> of time, well over several seconds (1 to 3 seconds typical) with gigabit, >>>> and >>>> having your ethernet connection go offline for 3 seconds may not be the >>>> desired >>>> effect for when you want to get more bandwidth in the first place. >>>> >>>> However, when a laptop is in battery mode, switching down from gigabit to >>>> 100mbit >>>> makes a lot more sense, so this is something I would recommend. This can >>>> be as >>>> easy as changing the advertisement mask of the interface and renegotiating >>>> the >>>> link. Userspace could handle that very easily. >>> Now if you were trying to transfer a lot of data to the laptop, would it >>> be more power efficient to do it at gigabit speeds so you can finish >>> sooner and shut down the machine entirely, or to slow to 100mbit and >>> take longer to do it, and hence spend more time powering the cpu and >>> ram? >> my suspicion is that the cost of switching is much higher than what you would >> consume running at 100mbit, even if the amount of data is quite large. going >> offline to renegotiate the link would already cost you 3W typically. >> >> I definately think that userspace is the right field to solve this problem: >> let >> the users decide how to use the available power on their sytems through a >> decent >> power profile tool (perhaps gnome-power-manager or something like that). >> This way >> the user can choose. >> > > Auke, > I was wondering if we could use PM-QOS to have the driver drop to the > 100Mb speed, when requests for bandwidth and latency are not in effect?
sure, that would probably work just fine. Technically this is not that hard anyway I suppose that HAL integration is lacking a bit and missing ethtool ioctl code for this which would be another solution - and would work without any driver changes. Auke - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
