[SOLVED] [cpu::cores] pct in v5 diverges from documentation

grin

Active Member
Dec 8, 2008
148
11
38
Hungary
grin.hu
In proxmox5 cpu setting have diverged from all the documentation.
It seems that cores setting is gone, as well as cpusets, and right now only cpulimit prevailed.

First, documentation thinks otherwise. Very probably should be updated.

Second, this may be a problem if the programs in the container behave erratically. This is only a theory, but what if:
  • the machine has 48 cores, and we plan to use 16 from those for a given container
  • the container see 48 cores (since no core setting anymore) and is being limited so that if all the 48 cores run at 10% then everything's fine (~480%), when it exceeds 1600% then threads get randomly limited
  • now, consider a big bad java thing. usually run plenty of harmless threads.
  • a few thread then gets jammed, pushing cpu 100% each. (business as usual for bad java code)
  • when the amount of jammed threads approach 16 all the non-jammed threads start to get starved since the jammed ones push cpu much stronger than them. the result is a hard-to-detect and hard-to-debug slowness of the whole system while it still responds, but not responsive anymore.
  • if there was a core:16 setting the machine would simply stop responding: out of cores, no more threads to run, pretty obvious to see.
 

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