Add option to mimic "ActiveProcessorCount" for older JVMs

[exalate-issue-sync]

Java 8u191 and later support JVM option ActiveProcessorCount, like this:

-XX:ActiveProcessorCount=2

#cpu cores affect built-in java thread pools and H2O uses it to determine parallelism of certain operations.

Because we do not have this option available in all Java versions, we want to be able mimic the behavior in h2o userspace code.

This will be for now independent of the {{nthreads}} argument option (we don’t want these 2 to clash).

[exalate-issue-sync]

Michal Kurka commented: Users will be able to use the system property {{-Dsys.ai.h2o.activeProcessorCount=x}}

and accomplish similar effect as -XX:ActiveProcessorCount=2.

[h2o-ops-ro]

JIRA Issue Details

Jira Issue: PUBDEV-8425
Assignee: Michal Kurka
Reporter: Michal Kurka
State: Resolved
Fix Version: 3.34.0.5
Attachments: N/A
Development PRs: Available

[h2o-ops-ro]

Linked PRs from JIRA

#5898