Mirroring via git-annex now takes much longer and causes high CPU load

Since some days (unfortunately can't specify, logs are gone for some reason), the time taken by mirroring periodic tasks increased a lot:

• git-annex-mirror-torbrowser-archive.service: 1min → 6 min
• git-annex-mirror-iso-history.service 26s → 17min

Also, they now occupy almost 2 full cores each while running (a constant load of 4).

High load is not expected, neither of them should ever be used intensely:

• torbrowser-archive: we upload to it once for each Tor Browser release, and some timer job is copying the stuff out from there to www.lizard http://www.lizard. so really the load should be minimal
• iso-history: also used mostly around release time, and should have minimal load normally

(Thanks anonym for that info!)

What changed lately:

• The VM was upgraded to Bookworm.
• FT started using git annex sync --no-content: tails@08625e83

FTR: I have increased the amount of cores of the VM for now so it can take the load meanwhile.

Cc: @foundations-team, in case they have more input to give. 😸