On Tue, Jun 22, 2010 at 12:37 PM, Luis R. Rodriguez <mcgrof@xxxxxxxxx> wrote: > 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. So defaults should always be sane and you should not have to play with this stuff, unless you're a hacker, or are testing something for development purposes. Tweaking ASPM settings is not something a user should have to worry about. Period. 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
