6888526 Linux getCurrentThreadCpuTime is drastically slower than Windows

[Andrew Haley]

I'm looking at this one.

The evaluation says:

"As the submitter notes the functionality exists but is disabled by
default. The user can easily enable it by specifying
-XX:+UseLinuxPosixThreadCPUClocks

"The functionality was added for JDK 6 under CR 6200022 but there was
concern at the time about enabling it by default (those concerns are
not documented in 6200022).

"Perhaps it is time to enable this feature by default?"

http://bugs.sun.com/view_bug.do?bug_id=6888526

Perhaps there was a problem with backwards compatibility: if that is
still the case, I can build and test on an old version of Red Hat
Enterprise Linux.  I suppose anything older than 2.6.10 will do.

The other question is whether the UseLinuxPosixThreadCPUClocks option
should be removed entirely.  I think it probably should, and we can
simply assume a kernel more recent than 2.6.10.  This is more of a
policy issue than a technical one, so I'm seeking guidance for this.

Andrew.