Re: 100 ms boot time increase regression in acpi_init()/acpi_scan_bus()

[Thorsten Leemhuis <regressions@leemhuis.info>]

Hi, this is your Linux kernel regression tracker speaking.

On 10.01.22 12:29, Paul Menzel wrote:
> #regzbot introduced: v5.13..v5.14-rc1
> #regzbot link: https://bugzilla.kernel.org/show_bug.cgi?id=215419

Thx for getting regzbot involved!

Nothing happened since you reported the issue three weeks ago; sure,
it's not a pressing issue, but I wonder what the status is.

@pm people: isn't this at least worth a reply?
@paul: did you perform any additional checks?

Or did anything happen somewhere else and I just missed it?

#regzbot poke

Ciao, Thorsten (wearing his 'Linux kernel regression tracker' hat)

P.S.: As a Linux kernel regression tracker I'm getting a lot of reports
on my table. I can only look briefly into most of them. Unfortunately
therefore I sometimes will get things wrong or miss something important.
I hope that's not the case here; if you think it is, don't hesitate to
tell me about it in a public reply, that's in everyone's interest.

BTW, I have no personal interest in this issue, which is tracked using
regzbot, my Linux kernel regression tracking bot
(https://linux-regtracking.leemhuis.info/regzbot/). I'm only posting
this mail to get things rolling again and hence don't need to be CC on
all further activities wrt to this regression.

> On the Intel T4500 laptop Acer TravelMate 5735Z with Debian
> sid/unstable, there is a 100 ms introduced between Linux 5.10.46 and
> 5.13.9, and is still present in Linux 5.15.5.
> 
>     [    0.000000] microcode: microcode updated early to revision 0xa0b,
> date = 2010-09-28
>     [    0.000000] Linux version 5.15.0-2-amd64
> (debian-kernel@lists.debian.org) (gcc-11 (Debian 11.2.0-13) 11.2.0, GNU
> ld (GNU Binutils for Debian) 2.37) #1 SMP Debian 5.15.5-2 (2021-12-18)
>     [    0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.15.0-2-amd64
> root=UUID=e17cec4f-d2b8-4cc3-bd39-39a10ed422f4 ro quiet noisapnp
> cryptomgr.notests random.trust_cpu=on initcall_debug log_buf_len=4M
>     […]
>     [    0.262243] calling  acpi_init+0x0/0x487 @ 1
>     […]
>     [    0.281655] ACPI: Enabled 15 GPEs in block 00 to 3F
>     [    0.394855] ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff])
>     […]
>     [    0.570908] initcall acpi_init+0x0/0x487 returned 0 after 300781
> usecs
> 
> I attached all the log files to the Kernel.org Bugzilla bug report
> #215419 [1].
> 
> Unfortunately, I am unable to bisect the issue, as it’s not my machine,
> and I do not have a lot of access to it.
> 
> Using ftrace, unfortunately, I didn’t save all of them, I think the path is
> 
>     acpi_init() → acpi_scan_init() → acpi_bus_scan(ACPI_ROOT_OBJECT)
> 
> But this path hasn’t changed as far as I can see. Anyway, from that
> path, somehow
> 
>     acpi_bus_check_add_1() → acpi_bus_check_add() → … →
> acpi_bus_check_add() → acpi_add_single_object() → acpi_bus_get_status()
> 
> is called, and the `acpi_bus_get_status()` call takes 100 ms on the
> system – also the cause for bug #208705 [2] –, but that code path wasn’t
> taken before.
> 
> Do you know from the top of your head, what changed? I am going to have
> short access to the system every two weeks or so, so debugging is
> unfortunately quite hard.
> 
> What is already on my to-do list:
> 
> 1.  Use dynamic debug `drivers/acpi/scan.c`
> 2.  Trace older Linux kernel (5.10.46) to see the differences
> 3.  Booting some GNU/Linux system to test 5.11 (Ubuntu 20.10) and 5.12
> 4.  Unrelated to the regression, but trace `acpi_bus_get_status()` to
> understand the 100 ms delay to solve bug #208705 [2]
> 
> 
> Kind regards,
> 
> Paul
> 
> 
> PS: Do you know of GNU/Linux live systems that are available for all
> Linux kernel releases and have an initrd, that just stores/uploads the
> output of `dmesg`?
> 
> 
> [1]: https://bugzilla.kernel.org/show_bug.cgi?id=215419
>      "100 ms regression in boottime before `ACPI: PCI Root Bridge [PCI0]"
> [2]: https://bugzilla.kernel.org/show_bug.cgi?id=208705
>      "boot performance: 100 ms delay in PCI initialization - Acer
> TravelMate 5735Z"
>