Good morning!

I spent some time figuring out why my build PC was running so slowly today. Thanks to some help from my very smart colleagues I came up with this testcase in Nushell to measure CPU performance:

~: dd if=/dev/random of=./test.in bs=(1024 * 1024) count=10
10+0 records in
10+0 records out
10485760 bytes (10 MB, 10 MiB) copied, 0.0111184 s, 943 MB/s
~: time bzip2 test.in
0.55user 0.00system 0:00.55elapsed 99%CPU (0avgtext+0avgdata 8044maxresident)k
112inputs+20576outputs (0major+1706minor)pagefaults 0swap

We are copying 10MB of random data into a file and compressing it with bzip2. 0.55 seconds is a pretty good time to compress 10MB of data with bzip2.

But! As soon as I ran a virtual machine, this same test started to take 4 or 5 seconds, both on the host and in the virtual machine.

There is already a new Fedora kernel available and with that version (6.17.4-200.fc42.x86_64) I don’t see any problems. I guess some issue affecting AMD Ryzen virtualization that got fixed already.

Have a fun day!