Request for review: 6888526 Linux getCurrentThreadCpuTime is drastically slower than Windows

[Daniel D. Daugherty]

Andrew,

I concur that it is time to change the default value for this flag
so thumbs up on the webrev.

My only worry is about HSX-19 deliveries into JDK-Updates. I'll
poke around and see if I can find a statement about the minimum
Linux that is supported.

The majority of the JVM/TI relevant tests are internal so those
won't do you much good. If you push this change to

     http://hg.openjdk.java.net/jdk7/hotspot-rt/hotspot

a.k.a. RT_Baseline, I can keep an eye on the internal test results.

Dan


On 7/7/2010 11:33 AM, Andrew Haley wrote:
> 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?"
>
> I changed the default for this parameter to true.
>
> I tested this change on an older Linux system that does not have the
> high-speed thread clock interface (Red Hat Enterprise Linux AS release
> 4, kernel 2.6.9).  The test case still works, but slowly.
>
> On a more recent system (Fedora 12, kernel 2.6.31) the test case is
> much speeded up.
>
> Is there any more testing that I should do?
>
> Patch at http://cr.openjdk.java.net/~aph/6888526/
>
> OK to push?
>
> Andrew.
>