Effect of setting CPU quota on Java performance (original) (raw)

Thomas Schatzl thomas.schatzl at oracle.com
Mon Feb 5 12:44:15 UTC 2018

Hi,

On Mon, 2018-02-05 at 11:18 +0530, Ashutosh Mehra1 wrote:

I have been trying to understand if setting CPU quota limit on a docker container, provided the "effective" CPUs are the same, has any impact on the application performance. As an example, if my app is running on 4 CPUs @ 100% quota, would I get same performance if my app is running on 8 CPUs at 50% quota? Note that "effective" CPUs is 4 in both cases.

I can imagine that using "half-cpus" has significant detrimental impact on latency: i.e. it would as far as I understand provising partial cpus increase the chance that during a safepoint threads will be scheduled out, or threads moved between cpus.

The container heuristics for choosing the number of threads do try to adapt for this (as your examples and results imply), but there likely still is the overhead of the (additional) reschedules.

Of course this might be dependent a lot on OS/kernel etc.

Thanks, Thomas

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