On Wed, 2013-07-10 at 13:57 -0600, Bjorn Helgaas wrote: > [+cc Jeff, Jesse, et al, e1000-devel] > > Holy cow, you guys have a lot of folks listed in MAINTAINERS for Intel > drivers :) This is an ASPM question, if that helps narrow down the > folks interested.
Bruce Allan is the e1000e maintainer, I have trimmed down the recipients. If you simply add e1000-devel mailing list, that will get to all of us and we can respond accordingly. I need to put together a patch to remove PJ because he is no longer in our group. > > On Wed, Jul 10, 2013 at 7:29 AM, Pavel Machek <[email protected]> wrote: > > Hi! > > > >> >> But: > >> >> 1) it should not list unavailable options > >> >> > >> >> 2) operation not permitted seems like wrong error code for > >> >> operation not supported. > >> > > >> > So I forcibly enabled ASPM, and now ping latencies are in normal > >> > range... no matter how I set > >> > /sys/module/pcie_aspm/parameters/policy. Strange. > >> > > >> > Any ideas what correct solution is? > >> > > >> > Pavel > >> > Signed-off-by: Pavel Machek <[email protected]> > >> > (but don't apply) > > ... > >> > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c > >> > index e4b1fb2..9a1b63e 100644 > >> > --- a/drivers/pci/pci-acpi.c > >> > +++ b/drivers/pci/pci-acpi.c > >> > @@ -382,7 +382,7 @@ static int __init acpi_pci_init(void) > >> > > >> > if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM) { > >> > printk(KERN_INFO"ACPI FADT declares the system doesn't > >> > support PCIe ASPM, so disable it\n"); > >> > - pcie_no_aspm(); > >> > +// pcie_no_aspm(); > >> > } > >> > > >> > ret = register_acpi_bus_type(&acpi_pci_bus); > >> > >> Hi Pavel, > >> > >> Interesting. Can you collect dmesg and "lspci -vvv" output for both > >> cases (high ping latency and normal ping latency)? > > > > Will do. Results are in attachment (200KB...) > > > >> Also, how much > >> difference does this make in ping latency? > > > > The ping latency goes from 100msec range to <2msec. > > > >> If ASPM is enabled for a > >> device, e.g., your NIC, the link may be put in a low power state when > >> the device is idle. It takes time to exit that low power state, of > >> course, but I would expect that time to be in the microsecond time and > >> probably not observable via ping. > > > > I'd hope so. 100msec ping makes ssh unpleasant to use. > > Pavel's ThinkPad X60 has two NICs: Intel 82573L and Intel PRO/Wireless > 3945ABG. I'm pretty sure the problem he's reporting is with the > 82573L. Ping times are bad (~100msec) when ASPM is enabled, as > reported by lspci. > > On Pavel's system, the FADT says we shouldn't enable OSPM control of > ASPM (ACPI_FADT_NO_ASPM is set), so we set "aspm_disabled = 1". One > effect is that we don't blacklist the pre-1.1 82573L device, which I > think results in it being left with the BIOS configuration, which > apparently has ASPM enabled. (Pavel, could you confirm the BIOS > config, e.g., with "pci=earlydump"?) > > e1000e claims to disable ASPM, but because aspm_disabled is set, the > driver's call to pci_disable_link_state_locked() actually does nothing > [1]. > > I experimented [2] with Windows and found that when a driver requests > PciASPMOptOut, Windows will not touch ASPM config if the _OSC method > fails, i.e., the BIOS declines to grant ASPM control to the OS. > However, I do not know if Windows similarly ignores PciASPMOptOut when > the FADT ACPI_FADT_NO_ASPM bit is set. > > The PCI core has failed spectacularly at providing useful ASPM > interfaces. Do you Intel folks have any suggestions about how to > resolve this? I assume that the Windows driver for the 82573L must > disable ASPM somehow, even though ACPI_FADT_NO_ASPM is set. Does it > just use brute-force, as in the version of __e1000e_disable_aspm() > that's used when CONFIG_PCIEASPM is not set? > > Bjorn > > [1] We just merged 2add0ec1, which adds a "can't disable ASPM; OS > doesn't have ASPM control" message in this case, but I don't think > Pavel's kernel has this change. It doesn't change the behavior > anyway. > > [2] https://bugzilla.kernel.org/show_bug.cgi?id=57331
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