[Bug 1665270] Re: Lower number of workers by default

[James Page]

I agree that capping the calculated value is probably a good idea; we
recently did this for the dataset size configuration in percona-cluster
(max out at 512M if the end-user does not provide any explicit
configuration).

We did discuss this a week or so ago - I think by default we should use
2 x the CPU's or 4 workers, whichever is lowest; if the charm user sets
worker-multiplier 0.5 or 8 (or anything else), then we will obey that
blindly, but the default unset configuration will cap at 4 workers.

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https://bugs.launchpad.net/bugs/1665270

Title:
  Lower number of workers by default

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Status in OpenStack neutron-gateway charm:
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Bug description:
  On containerized setups with multiple cpus and hyperthreading on the
  metals the containers can see a large number of cores. With the
  default worker multiplier settings this eg. results in 112 workers
  plus a leader processes on one of our installs. With HA we have then
  3x113 processes serving in total, which is a bit of a waste (3x16G of
  RSS for one service, as an example)

  While this can be tuned down I'd suggest to cap the number of workers
  when the worker-multiplier setting is on default to make this more
  sensible out of the box

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