On Tue, Jun 22, 2010 at 12:31 PM, Johannes Stezenbach <js@xxxxxxxxx> wrote: > On Tue, Jun 22, 2010 at 07:44:26PM +0100, Matthew Garrett wrote: >> On Tue, Jun 22, 2010 at 11:28:20AM -0700, Luis R. Rodriguez wrote: >> > >> > Heh, this whole patch and thread was started because Jussi tested >> > ath5k with pcie_aspm=force (on a pre PCIE 1.1 device (?)) . I have >> > been trying to explain all along why this is a terrible idea to the >> > point we should probably just remove that code from the kernel. Hence >> > my side rants and explanations to justify my reasonings. >> >> Well, there's two things here. If you use force then you might get >> inappropriate ASPM. But if your BIOS enables ASPM on an old device, then >> booting *without* CONFIG_PCIE_ASPM will leave it turned on, and booting >> *with* CONFIG_PCIE_ASPM will turn it off. The Kconfig description is >> confusing - reality is that CONFIG_PCIE_ASPM enables logic that allows >> the kernel to modify the BIOS default, and disabling it makes the >> assumption that your BIOS did something sensible. > > Does CONFIG_PCIEASPM provide a way for the user to modifiy > the settings at runtime? You can tune ASPM settings at runtime, regardless of CONFIG_PCIEASPM. See: http://kernel.org/pub/linux/kernel/people/mcgrof/aspm/enable-aspm http://wireless.kernel.org/en/users/Documentation/ASPM > I have a Samsung N130 netbook which has a BIOS setting > called "CPU Power Saving Mode". When enabled it activates > ASPM L1 and L0s for the ethernet chip (Realtek RTL8102e, 100Mbit) > and the PCIE bridge (with the BIOS setting off it's just L1). > The result is that the ethernet througput is reduced to 25Mbit/s. > (The BIOS setting does not activa L0s for the Atheros AR9285 WLAN.) > > 99,9% of the time I want to enjoy the power savings, > but occationally I have to transfer some bulk data and would > like to switch the setting for a few minutes. > > Or, well, ideally I'd like to have power savings _and_ performance > at the same time without any manual intervention. I'm not sure > if this is a quirk of the N130 or if ASPM L0s always causes > performance degradation? L0s is not going to buy you much gains, getting at least L1 will however. L0s is just a further enhancement. I recommend you test by enabling L1 and L0s, check how longer your battery lasts and then test again with just L1. Then test without both L1 and L0s. Luis -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
