Kernel 5.9.1 slow switching TTY users

theGreaterDuck

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Linux Mint 20.0.4, Lenovo Flex 5, Ryzen 5 4500, 16GB, 512GB-SSD -- always up to date

I have to use a Kernel later than Ubuntu/Mint maintained stock 5.4.xx as it would not recognize external monitors with the Ryzen CPU.
Starting with Kernel 5.6.xx it all worked fine so I kept updating to the latest Kernel.

Up until Kernel 5.8.8 the switching between 2-active TTY user logins has taken less than a second.

From 5.8.9 to the just installed latest 5.9.1, switching is taking more than 3-seconds.

I have to keep rolling back to 5.8.8 as I need to switch users hundreds of times a day and it is irritating looking at black screens for a collective half hour per day.

Is there a setting or something I can adjust some way to get back to that fast switching and keep up with the latest Kernels?

Thanks
 


f33dm3bits

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This is probably the easiest way in Ubuntu/Mint to install the latest kernels. Otherwise you might be better off switching to a rolling release distribution since with rolling releases distributions the default kernel is usually the latest or close to the latest.
 

theGreaterDuck

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This is probably the easiest way in Ubuntu/Mint to install the latest kernels. Otherwise you might be better off switching to a rolling release distribution since with rolling releases distributions the default kernel is usually the latest or close to the latest.
Umm, don't mean to be rude, but did you read the OP? I am OK with installing the .deb files and have been doing so since 5.6.xxx

IF I roll back to 5.8.8 or ANYTHING earlier as far back as 5.6.xx it switches fast.

Everything since 5.8.8 is taking 3+ seconds per switch -- up to and INCLUDING 5.9.1.which I installed this morning and un-installed this afternoon.

I am looking for help to get that switching speed back in 5.8.9 through 5.9.1, not how to install or maintain the Kernels.
 

f33dm3bits

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I don't mean to be rude either but not everyone's first language is English. So it can happen that I misread things or read over things, I see that I missed something now that I read it again. You could pin the package providing your kernel so it doesn't get updated, but since you still want the most recent kernels and have the same speed when switching with tty user sessions as with the earlier kernels you mentioned that doesn't sound like an option. So then you will have to figure out what's causing the delay of tty switching with the newer kernels. I would start by looking for kernel messages with amdgpu or other kernel messages that stand out.
 
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theGreaterDuck

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You could pin the package providing your kernel so it doesn't get updated
Thanks, that is taken care of by the Mint Update/Upgrade as it ignores all Kernels except for the 5.4.xx version that Ubuntu maintains. I regularly download the latest batch of Kernel .deb files and manually install them.

So then you will have to figure out what's causing the delay of tty switching with the newer kernels.
:D thanks also, but that's why I am here. I am out of my depth messing around at this level and would like some explicit instructions.

I am not worried about crashing and trashing as I am OK with restoring or even re-installing if I break something. When you say, I would start by looking for kernel messages with amdgpu where and with what would I start looking?

I have been forced into this Kernel wilderness (for me) by the Lenovo+Ryzen+Linux combo, so trial, error and winging it are my only current directions.

AMD and/or Lenovo have not yet come to the party with the Renior graphics drivers for Linux. So a later Kernel is my current only option or put this laptop on a shelf and wait for AMD catch up.

It's all good fun. :)
 

f33dm3bits

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You can check for those log messages in both /var/log/syslog and journalctl(by running it on the command-line), as wel as my running dmesg. Try switching user then check syslog/journalctl and dmesg for any messages related to amdgpu and other kernel messages that stand out.
 

theGreaterDuck

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OK, did that and as far as I can tell File-Compare on the 2 "dmesg" were the same. The amdgpu and Renior verisions matched, memory allocation matched as did pretty much everything else.

Is there any great security risk by staying with 5.8.8? The last of the fast switching.

I am off to put 5.8.8. at the front of the queue again. :)
 

f33dm3bits

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There is no point in comparing dmesg and syslog/journalctl when trying to switch user tty session since they are both system wide log information. It would actually be useful to see some actual output you got from both dmesg and journal/syslog. Filter for messages with amdgpu or kernel in it . Kernel 5.8.x is still supported so updates and security updates will continue to be released, so yes there is a risk if they patch a security hole which still is in your current running kernel which they fixed in the next minor release.

Isn't it easier to have 5.8.8 configured as your default booting kernel so that what you test a new kernel you can just easily switch when booting, and if it doesn't work with the new kernel reboot and that it automatically boots into 5.8.8.
 

theGreaterDuck

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Thanks again. I just learned how to set 5.8.8 as the default Kernel to boot. A bit messy, but works.

The problem with 5.8.8 -- I can't update it as the next update is 5.8.9 and that has the slow switching as does everything that follows. So whatever is doing it, it started with 5.8.9.

I had tried the Filtering for "amdgpu" and that's what I was comparing on. I'll try again and post stuff here. Is there anything in particular you are looking for? There are a lot of lines with "amdgpu" in them.
 

theGreaterDuck

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OK, wrote a rough and dirty program to filter out all the "amdgpu" lines into a separate file for each kernel.
Attached. What other files should I do for you and what besides "amdgpu?"
5.5.8-syslog fast switching
5.9.0-syslog slow switching
 

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f33dm3bits

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I'm not a kernel expert either but I can't find anything that looks strange with those log lines with in amdgpu it. Can you also just send do a filter on every line containing kernel in it while in both kernels after having switched tty sessions.
 

f33dm3bits

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Couldn't find anything strange kernel messages either, I would just wait for the next kernel update to see if your problem is fixed there. What you could try and do is live boot from a different distribution, for example EndeavourOS or Aco, and try the tty user switching there and see if you have the same problem there. If you don't have the problem there it could be that the the kernel you are for Mint was compiled with different options on or off or something like that. Don't know how you installed the newer kernel under Mint, it's not a solution but it might give you an answer.
 

theGreaterDuck

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I would just wait for the next kernel update to see if your problem is fixed there.
Thanks, but it changed at 5.8.9, 5.8.10, 5.8.11 all the way up to 5.8.17, then 5.9.0 and 5.9.1 when they were released and **all** of them have the slow switching. I see there is a 5.9.2. I will install that and see, or just stay with 5.8.9 and any/all security warts.

Yes, Mint is compiled with the Ubuntu-maintained 5.4.52 (currently) but I cannot use it with Ryzen and the old Mesa video drivers with 5.4.xx for external monitors.
 


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