Message-ID: <51e0d018-f4c5-4a2d-93bd-265b4c13415f@molgen.mpg.de>
Date: Fri, 21 Feb 2025 23:13:32 +0100
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Juri Lelli <juri.lelli@...hat.com>
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 LKML <linux-kernel@...r.kernel.org>
Subject: Re: Linux warns `sched: DL replenish lagged too much`

Dear Juri,


Am 20.02.25 um 21:18 schrieb Paul Menzel:

> Am 20.02.25 um 14:35 schrieb Juri Lelli:
> 
>> On 20/02/25 11:47, Paul Menzel wrote:
> 
>>> On the Intel Kaby Lake laptop Dell XPS 13 with Linux
>>> 6.14.0-rc3-00060-g6537cfb395f3, waking it up from ACPI S3 with an LMP  USB-C
>>> mini dock connected, that had an Ethernet cable and a power adapter plugged
>>> in, everything was lagging, and also the video in the opened Firefox Nightly
>>> browser lagged quite a bit. This has happened in the past, but not  that bad
>>> and long. Today for the first time, Linux logged the warning below:
>>>
>>>      sched: DL replenish lagged too much
>>>
>>> (This is from `kernel/sched/deadline.c`.)
>>>
>>> I have no idea, if it’s related to the hardware itself, that causes it to
>>> lag, that a suspend/resume cycle fixes, or if it’s related to the USB-C
>>> controller that has bugs in that early generation, or if it’s related to
>>> GNOME/Mutter (*mutter-common* 48~beta-3) or Firefox or the Web video player
>>> used by the site.
>>>
>>> As often the case with this, I have no way to reliably reproduce it, and in
>>> this case to reproduce the warning. I can only say, that this warning has
>>> not been logged in the available log files since September 2024. Linux
>>> “6.11-rc0” was used then. Please find the log messages attached.
>>>
>>> In case this information is not useful, should this happen again, it’d be
>>> great if you could suggest what and how I should collect debugging
>>> information next time.
>>
>> Assuming no explicit usage of SCHED_DEADLINE, I would say the warning
>> message might be related to the recently introduced deadline servers:
>> 5f6bd380c7bd ("sched/rt: Remove default bandwidth control") and related
>> commits.
>>
>> They were merged in v6.12 (IIRC), though,
> 
> Indeed, it first appeared in v6.12-rc1.
> 
>> so I would expect you had noticed already before if they introduced
>> issues on your setup? That said, it might also be the case that
>> something else changed more recently that now triggers a corner
>> case.
> 
> On this device, I sometimes experience lags after resuming from ACPI S3, 
> and, although I cannot prove it, using USB-C mini docks (LMP USB-C mini 
> Dock [1] or Dell DA300) seems to increase the chances of hitting the 
> problem. Re-plugging and doing ACPI S3 suspend/resume again often helps.

I guess, I didn’t see this yet, as I haven’t been using the USB-C 
charger with the USB-C mini dock up until now as the laptop also has a 
barel jack for charging.

>> The warning message per-se it's not fatal, it just warns that the kernel
>> is recovering from an unexpected situation. Did you notice that things
>> went back to normal (no lag from a user perspective) right after that
>> message was printed?
> 
> As far as I remember, the lagging stayed even after the log was printed. 
> In this case, I had to reboot the device, and until now – with no ACPI 
> S3 suspend/resume – it works fine.

I was able to reproduce this today. The same behavior after resuming 
from ACPI S3.

     Feb 21 17:20:19 abreu gnome-shell[1775]: 
meta_wayland_buffer_process_damage: assertion 'buffer->resource' failed
     Feb 21 17:20:19 abreu gnome-shell[1775]: 
(../src/wayland/meta-wayland-buffer.c:709):meta_wayland_buffer_inc_use_count: 
runtime check failed: (buffer->resource)
     Feb 21 17:20:21 abreu rtkit-daemon[1017]: Supervising 7 threads of 
5 processes of 1 users.
     Feb 21 17:20:21 abreu rtkit-daemon[1017]: Supervising 7 threads of 
5 processes of 1 users.
     Feb 21 17:20:59 abreu kernel: sched: DL replenish lagged too much
     Feb 21 17:21:01 abreu systemd[1588]: Started 
app-gnome-ptyxis-26577.scope - Application launched by gsd-media-keys.
     […]
     Feb 21 17:23:43 abreu gnome-shell[1775]: libinput error: event11 - 
DLL075B:01 06CB:76AF Touchpad: client bug: event processing lagging 
behind by 31ms, your system is too slow

Move lags sometimes, and also switching GNOME virtual desktops, or just 
opening a new window takes several seconds.

Can I set an option so more stuff is logged, once the scheduler warning 
is logged?


Kind regards,

Paul


> [1]: https://lmp-adapter.com/product/lmp-usb-c-mini-dock/

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