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? --mgross - 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/
