Date:	Thu, 05 Sep 2013 16:17:25 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>, Jiang Liu <liuj97@...il.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: Excess dmesg output from ACPIPHP on boot (was: Re: [PATCH
 25/30] ACPI / hotplug / PCI: Check for new devices on enabled slots)

On Thu, 2013-09-05 at 23:39 +0200, Rafael J. Wysocki wrote:
> On Thursday, September 05, 2013 09:44:26 PM Rafael J. Wysocki wrote:
> > On Thursday, September 05, 2013 08:21:41 AM Alex Williamson wrote:
> 
> [...]
> 
> > > > 
> > > > [   18.288122] pci 0000:00:00.0: no hotplug settings from platform
> > > > [   18.288127] pcieport 0000:00:01.0: no hotplug settings from platform
> > > > [   18.288142] pci 0000:01:00.0: no hotplug settings from platform
> > > > [   18.288157] pci 0000:01:00.1: no hotplug settings from platform
> > > > [   18.288162] pcieport 0000:00:03.0: no hotplug settings from platform
> > > > [   18.288176] pci 0000:02:00.0: no hotplug settings from platform
> > > > [   18.288190] pci 0000:02:00.1: no hotplug settings from platform
> > > > [   18.288195] pcieport 0000:00:07.0: no hotplug settings from platform
> > > > [   18.288209] pci 0000:03:00.0: no hotplug settings from platform
> > > > [   18.288224] pci 0000:03:00.1: no hotplug settings from platform
> > > > [   18.288228] pci 0000:00:14.0: no hotplug settings from platform
> > > > [   18.288233] pci 0000:00:14.1: no hotplug settings from platform
> > > > [   18.288237] pci 0000:00:14.2: no hotplug settings from platform
> > > > [   18.288242] pci 0000:00:16.0: no hotplug settings from platform
> > > > [   18.288247] pci 0000:00:16.1: no hotplug settings from platform
> > > > [   18.288251] pci 0000:00:16.2: no hotplug settings from platform
> > > > [   18.288256] pci 0000:00:16.3: no hotplug settings from platform
> > > > [   18.288260] pci 0000:00:16.4: no hotplug settings from platform
> > > > [   18.288265] pci 0000:00:16.5: no hotplug settings from platform
> > > > [   18.288269] pci 0000:00:16.6: no hotplug settings from platform
> > > > [   18.288274] pci 0000:00:16.7: no hotplug settings from platform
> > > > [   18.288278] pci 0000:00:1a.0: no hotplug settings from platform
> > > > [   18.288279] pci 0000:00:1a.0: using default PCI settings
> > > > [   18.288292] pci 0000:00:1a.1: no hotplug settings from platform
> > > > [   18.288293] pci 0000:00:1a.1: using default PCI settings
> > > > [   18.288307] ehci-pci 0000:00:1a.7: no hotplug settings from platform
> > > > [   18.288308] ehci-pci 0000:00:1a.7: using default PCI settings
> > > > [   18.288322] pci 0000:00:1b.0: no hotplug settings from platform
> > > > [   18.288327] pcieport 0000:00:1c.0: no hotplug settings from platform
> > > > [   18.288332] pcieport 0000:00:1c.4: no hotplug settings from platform
> > > > [   18.288344] pci 0000:05:00.0: no hotplug settings from platform
> > > > [   18.288349] pci 0000:00:1d.0: no hotplug settings from platform
> > > > [   18.288350] pci 0000:00:1d.0: using default PCI settings
> > > > [   18.288360] pci 0000:00:1d.1: no hotplug settings from platform
> > > > [   18.288361] pci 0000:00:1d.1: using default PCI settings
> > > > [   18.288374] pci 0000:00:1d.2: no hotplug settings from platform
> > > > [   18.288374] pci 0000:00:1d.2: using default PCI settings
> > > > [   18.288387] pci 0000:00:1d.3: no hotplug settings from platform
> > > > [   18.288387] pci 0000:00:1d.3: using default PCI settings
> > > > 
> > > > The boot is noticeably slower.  What's going to happen on systems that
> > > > actually have a significant I/O topology vs my little workstation?
> > 
> > That depends on how many bus check/device check events they generate on boot.
> > 
> > My test machines don't generate them during boot at all (even the one with
> > a Thunderbolt connector), so I don't see the messages in question during boot
> > on any of them.  Mika doesn't see them either I suppose, or he would have told
> > me about that before.
> > 
> > And let's just make it clear that it is not usual or even OK to generate bus
> > checks or device checks during boot like this.  And since the changes in
> > question have been in linux-next since right after the 3.11 merge window, I
> > think that someone would have complained already had that been a common issue.
> > 
> > Of course, we need to deal with that somehow nevertheless. :-)
> > 
> > > Just to give you an idea:
> > > 
> > > CONFIG_HOTPLUG_PCI_ACPI=y
> > > 
> > > $ dmesg | wc
> > >   5697  49935 384368
> > > 
> > > $ dmesg | tail --lines=1
> > > [   53.137123] Ebtables v2.0 registered
> > > 
> > > -- vs --
> > > 
> > > # CONFIG_HOTPLUG_PCI_ACPI is not set
> > > 
> > > $ dmesg | wc
> > >  1053  9176 71652
> > > 
> > > $dmesg | tail --lines=1
> > > [   28.917220] Ebtables v2.0 registered
> > > 
> > > So it spews out 5x more output with acpiphp enabled and takes and extra
> > > 24s to boot (nearly 2x).  Not good.
> > 
> > The "no hotplug settings from platform" message is from pci_configure_slot().
> > I think the messages you're seeing are from the call to it in
> > acpiphp_set_hpp_values() which is called by enable_slot().
> > 
> > There, I think, we can simply check the return value of pci_scan_slot() and
> > if that is 0 (no new devices), we can just skip everything under the call to
> > __pci_bus_assign_resources().
> > 
> > However, we can't skip the scanning of bridges, if any, because there may be
> > new devices below them and I guess that's what takes so much time on your
> > machine.
> 
> OK, one piece is missing.  We may need to evaluate _OSC after handling each
> event to let the platform know the status.
> 
> Can you please check if the appended patch makes any difference (with the
> previous fix applied, of course)?
> 
> If fact, it is two patches combined.  One of them optimizes enable_slot()
> slightly and the other adds the missing _OSC evaluation.

Better, still double the output:

$ dmesg | wc
   2169   19047  152710

$ dmesg | tail --lines=1
[   39.980918] Ebtables v2.0 registered

Here's another interesting stat:

$ dmesg | colrm 1 15 | sort | uniq -c | sort -nr | head --lines=25
     73 pci 0000:00:1f.0: BAR 13: [io  0x1000-0x107f] has bogus alignment
     73 pci 0000:00:1e.0: PCI bridge to [bus 06]
     64 pci 0000:00:1e.0:   bridge window [mem 0x81100000-0x812fffff 64bit pref]
     64 pci 0000:00:1e.0:   bridge window [mem 0x80f00000-0x810fffff]
     64 pci 0000:00:1e.0:   bridge window [io  0x7000-0x7fff]
     38 pci 0000:00:1c.4: PCI bridge to [bus 05]
     38 pci 0000:00:1c.4:   bridge window [mem 0xf4f00000-0xf4ffffff]
     38 pci 0000:00:1c.0: PCI bridge to [bus 04]
     38 pci 0000:00:07.0: PCI bridge to [bus 03]
     38 pci 0000:00:07.0:   bridge window [mem 0xf2000000-0xf40fffff]
     38 pci 0000:00:07.0:   bridge window [mem 0xe0000000-0xf1ffffff 64bit pref]
     38 pci 0000:00:07.0:   bridge window [io  0x4000-0x4fff]
     38 pci 0000:00:03.0: PCI bridge to [bus 02]
     38 pci 0000:00:03.0:   bridge window [mem 0xf4e00000-0xf4efffff]
     38 pci 0000:00:03.0:   bridge window [mem 0xd0000000-0xdfffffff 64bit pref]
     38 pci 0000:00:03.0:   bridge window [io  0x3000-0x3fff]
     38 pci 0000:00:01.0: PCI bridge to [bus 01]
     38 pci 0000:00:01.0:   bridge window [mem 0xf4100000-0xf4bfffff]
     38 pci 0000:00:01.0:   bridge window [io  0x2000-0x2fff]
     37 pci 0000:00:1c.4:   bridge window [mem 0x80c00000-0x80dfffff 64bit pref]
     37 pci 0000:00:1c.4:   bridge window [io  0x6000-0x6fff]
     37 pci 0000:00:1c.0:   bridge window [mem 0x80a00000-0x80bfffff 64bit pref]
     37 pci 0000:00:1c.0:   bridge window [mem 0x80800000-0x809fffff]
     37 pci 0000:00:1c.0:   bridge window [io  0x5000-0x5fff]
     36 pci 0000:00:01.0:   bridge window [mem 0x80000000-0x807fffff 64bit pref]

This is nearly the entire difference, just 25 lines repeated over and
over.  Thanks,

Alex

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