All Questions(ubuntu)

I have encountered a performance regression running the python interpreter when upgrading from ubuntu 18 to ubuntu 24. What do you think causes this? Is there a fix or workaround?

I have some evidence that suggests changes to the linux kernel--and not anything in userland--are likely responsible for the problem.

I can reproduce the performance discrepancy with a very simple test:

python3 -c "import timeit; print(timeit.Timer('for _ in range(0,1000): pass').timeit())"

I am running this test by booting off ubuntu 18 live server and ubuntu 24 live server ISOs on the very same Cisco UCS C220 M5SX rack system. You can find the live server ISOs on Canonical's site and reproduce the experiment.

I have a set of python 3.11 binaries built from source on a debian squeeze system that will run on a huge variety of linux distros. This gives me the opportunity to test the very same python binaries on 18 and 24. We will call these python binaries python_pegged. We will call the python3 fetched by 'apt-get' python_sys.

I have also tried running the ubuntu:18.04 docker container from within ubuntu 24 -- it has the bad performance characteristics of ubuntu 24 and does not behave like ubuntu 18, which leads me to believe userland is not responsible.

Experimental results:

Ubuntu 18.04.6 bare metal                            python_sys        13 seconds
Ubuntu 18.04.6 bare metal                            python_pegged     13 seconds
Ubuntu 18.04.6 bare metal                  sysbench --test=cpu run   1288 events/s
Ubuntu 24.04   bare metal                            python_sys        83 seconds
Ubuntu 24.04   bare metal                            python_pegged    112 seconds
Ubuntu 24.04   bare metal                  sysbench --test=cpu run    925 events/s
ubuntu:18.04 docker container hosted by Ubuntu 24.04 python_sys        82 seconds
ubuntu:18.04 docker container hosted by Ubuntu 24.04 python_pegged    112 seconds

In ubuntu 24, taking the following actions had zero effect:

• set scaling_governor to performance
• tuned-adm profile throughput-performance
• tuned-adm profile virtual-host
• tuned-adm profile balanced

The system has 40 physical cores and 80 hyperthreaded. I tried running various numbers of concurrent instances.

concurrent instances      seconds
                  40       82..83
                  80       53..53
                 120      87..115

I am surprised that 80 instances are faster than 40. I ran the experiment a couple times and the results never changed. I tried different tuned profiles with no effect. 53 seconds is still a far cry from ubuntu18's 13.

python is tripping over something expensive with ubuntu24 that sysbench is not--or at least not to the same degree. I may start using a profiler in the near future to dig deeper.

Testing of various intermediate versions indicates the regression occurred in the 21 -> 22 upgrade.

perf stat -a results on the python3 command:

Some big differences there. I'm not convinced 6 context switches per second really moves the needle. Instructions per cycle is presumably the most relevant data point here.

Kernel version updates causes auto unlock to break. I've configured my Ubuntu 22.04 box to auto update weekly with unattended upgrades. On newer kernel updates e.g.:

│ Newer kernel available
│ 
│ The currently running kernel version is 5.15.0-118-generic which is not the expected kernel version 5.15.0-119-generic.
│                                                                                                                                                        
│ Restarting the system to load the new kernel will not be handled automatically, so you should consider rebooting.

auto unlock does not work. The issue seems to be that kernel updates forces a reboot to apply updates, but cannot be finished without manually typing in the disk encryption password. Once rebooted, I have to resetup disk encryption by first running: sudo clevis luks unbind -d <partition> -s <SLOT_NUMBER> and then doing resetup of crypt setup by running: clevis luks bind -d <partition> tpm2 { "pcr_bank":"sha256", "pcr_ids": "<pcr_ids>" }' and update-initramfs -u -k 'all'. It doesn't seem to matter if we generate a boot image with update-initramfs before reboot or not. If I run clevis luks list -d <partition> I can see that the output is correct. Searching for this issue did not result in any hits. Is there any configuration that I would be missing or any configuration I could add?

1. On Ubuntu 22.04 setup disk encryption with auto unlock.
2. Run sudo apt update and sudo apt upgrade to trigger a kernal version update.
3. Reboot
4. On boot disk encryption password is requested.

Packages installed:

clevis
clevis-luks
clevis-initramfs
clevis-systemd
clevis-tpm

I can't connect to the internet neither using wired connection nor USB modem (desktop PC, no wifi). Checked status of NetworkManager - it works. But internet still unavailable. Tried different approaches - interface adding, netplan using and other - didn't help. What should I do?

I am connected over ssh to remote ubuntu and am trying to cat file content on ubuntu 24.04 machine into clipboard on my MacOS.

On my local OSX machine, I ssh into server and execute:

cat /usr/share/doc/apache2/README.Debian | xclip -selection clipboard

This causes an error: Can't open display: (null)

I tried sshing with -X flag, same problem.

I can copy the files over with stfp, but it would nice to do it with a clipboard instead. Is xclip capable of doing cross OS clipboard copying?

For a course, I am using the Racket language, which bundles its own IDE (Dr Racket) with the install. I successfully installed it on my Ubuntu 22.04 machine.

However, the installer does not create a mimetype for .rkt files (the default extension for Racket code files used by the IDE). I wanted my .rkt files to open in the Racket IDE when I click on them, so I created a custom mimetype, called text/rkt, which worked fine. The custom icon works and when I double click the files they open in the Racket IDE. On code files I've already created with code inside them, the custom mimetype seems to work correctly.

However, if I do touch test.rkt for example to create a new file, this file gets assigned the text/plain mimetype and when I double click it, it opens the text editor instead of the Racket IDE. This is not ideal, because I would like to be able to create empty files from the terminal and open them in the IDE (it's more convenient than doing Save As -> whatever every time in the IDE).

Is it possible to have my empty files with the *.rkt extension be recognized as my custom mimetype, instead of as plain text?

Here's the code for my custom mime type in case I did something wrong:

<?xml version="1.0" encoding="UTF-8"?>
<mime-info xmlns='http://www.freedesktop.org/standards/shared-mime-info'>
        <mime-type type="text/rkt">
                <comment>Racket code file</comment>
                <glob pattern="*.rkt"/>
        </mime-type>
</mime-info>

I followed the Ubuntu documentation here which I can see was last edited in 2014, as well as a post here which is more recent but maybe something changed since then. I'm new to linux so maybe I don't know where to look to find the correct instructions.