6888526 Linux getCurrentThreadCpuTime is drastically slower than Windows

[Andrew Haley]

On 07/05/2010 03:27 PM, Andrew Haley wrote:
> 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.

I just tried, and the current OpenJDK won't even build on Red Hat
Enterprise Linux Version 4, which is what we'd need to do to test a
system without pthread_getcpuclockid().  It won't build because a
version of Freetype greater than 2.3.0 is required, and RHEL 4 has
1.6.3.

I suggest that I should simply change the default of
UseLinuxPosixThreadCPUClocks to true, but leave the rest of the
scaffolding in place in case someone needs to disable it.

OK?

Andrew.