linux-kernel - Re: `pci_apply_final_quirks()` taking half a second

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Date:   Fri, 29 Dec 2017 11:14:51 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Bjorn Helgaas <helgaas@...nel.org>
cc:     Paul Menzel <pmenzel+linux-pci@...gen.mpg.de>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        <linux-usb@...r.kernel.org>
Subject: Re: `pci_apply_final_quirks()` taking half a second

On Thu, 28 Dec 2017, Bjorn Helgaas wrote:

> On Tue, Dec 26, 2017 at 04:55:20PM +0100, Paul Menzel wrote:
> > Am 08.04.2017 um 17:41 schrieb Bjorn Helgaas:
> > >On Fri, Apr 07, 2017 at 11:07:15PM +0200, Paul Menzel wrote:
> > 
> > >>Measuring where time is spent during boot with `systemd-bootchart`
> > >>on an Asus A780FullHD, it turns out that half a second is spent in
> > >>`pci_apply_final_quirks()`.
> > >
> > >I agree, that seems like a crazy amount of time.
> > >
> > >Can you figure out how to turn on pr_debug() (via the dynamic debug
> > >mess or whatever) and boot with "initcall_debug"?  That should tell us
> > >how long each quirk took.
> > 
> > I am sorry for taking so long to reply. I finally added `dyndbg=file
> > quirks.c +p` to the command line of Linux 4.13.13. This is on
> > another AMD system (Asus F285M Pro).

> > Dez 26 16:21:46 asus-f2a85-pro kernel: pci fixup
> > quirk_usb_early_handoff+0x0/0x6b0 returned after 197 usecs for
> > 0000:00:10.0
> > Dez 26 16:21:46 asus-f2a85-pro kernel: pci fixup
> > quirk_usb_early_handoff+0x0/0x6b0 returned after 127 usecs for
> > 0000:00:10.1
> > Dez 26 16:21:46 asus-f2a85-pro kernel: pci fixup
> > quirk_usb_early_handoff+0x0/0x6b0 returned after 88643 usecs for
> > 0000:00:12.0
> > Dez 26 16:21:46 asus-f2a85-pro kernel: pci fixup
> > quirk_usb_early_handoff+0x0/0x6b0 returned after 137 usecs for
> > 0000:00:12.2
> > Dez 26 16:21:46 asus-f2a85-pro kernel: pci fixup
> > pci_fixup_amd_ehci_pme+0x0/0x30 returned after 1 usecs for
> > 0000:00:12.2
> > Dez 26 16:21:46 asus-f2a85-pro kernel: pci fixup
> > quirk_usb_early_handoff+0x0/0x6b0 returned after 85770 usecs for
> > 0000:00:13.0
> > Dez 26 16:21:46 asus-f2a85-pro kernel: pci fixup
> > quirk_usb_early_handoff+0x0/0x6b0 returned after 134 usecs for
> > 0000:00:13.2
> > Dez 26 16:21:46 asus-f2a85-pro kernel: pci fixup
> > pci_fixup_amd_ehci_pme+0x0/0x30 returned after 1 usecs for
> > 0000:00:13.2
> > Dez 26 16:21:46 asus-f2a85-pro kernel: pci fixup
> > quirk_usb_early_handoff+0x0/0x6b0 returned after 125 usecs for
> > 0000:03:00.0[…]
> > ```
> > 
> > So it’s `pci fixup quirk_usb_early_handoff` taking around 85 ms, and
> > that twice.
> 
> Wow.  That's pretty painful, but of course I don't know how to fix it.
> From looking at quirk_usb_early_handoff(), it may depend on BIOS
> details.  Maybe the USB folks will have some ideas.

Can we see the output from lspci?  It would help to know what the 12.0 
and 13.0 devices are.

Alan Stern