slowness of profitbricks-build9-amd64.debian.net aka 46.16.78.222

[Helmut Grohne]

Hi,

I am using the node profitbricks-build9-amd64.debian.net aka
46.16.78.222 on behalf of the Debian project for performing QA. Around
three weeks ago, it started failing all jenkins jobs and we've been
researching the cause. It seems to have to do with the machine itself,
which is sponsored by profitbricks, which is now ionos and the reason
I'm writing to you. I'd like to use the opportunity to thank you for
this (otherwise reliable) service to the open source community.

cpuinfo indicates that it runs an AMD Opteron 62xx at 2.6 GHz. A very
simple method to check the performance of the cpu is using "openssl
speed -evp 256 -bytes 8192". Doing so yields the following numbers:

profitbricks-build9: AMD Opteron 62xx at 2.6 GHz
Doing sha256 for 3s on 8192 size blocks: 12936 sha256's in 3.00s
some i5 at 3 GHz
Doing sha256 for 3s on 8192 size blocks: 113152 sha256's in 3.00s
some i7 at 4 GHz
Doing sha256 for 3s on 8192 size blocks: 197063 sha256's in 3.00s
some i7 at 3.4 GHz
Doing sha256 for 3s on 8192 size blocks: 179561 sha256's in 3.00s

For some reason, the profitbricks system is around 10 times slower than
expected on this benchmark. We're using the system to compile software
(i.e. mostly running gcc) and we see a comparable slowness there. It
wasn't like that before. The symptoms started around 22 days ago. I
checked that there is no frequency scaling or throttling involved in the
sysfs.

Can you shed light on the issue? What can you suggest to diagnose the
problem?

Thanks for your help

Helmut