Re: must-fix list for 2.6.0

[Bill Huey \]

On Wed, Apr 30, 2003 at 10:40:22PM -0700, Dave Hansen wrote:
> Gerrit Huizenga wrote:
> > Which affects JVM in most cases.  NPTL based JVMs will possibly
> > obviate that problem.  My guess is that in the JVM case, they have
> > a bad locking model (er, a simpler 2-tier locking model instead of
> > a more correct and complex 3-tier locking model) for their threading
> > operations.  As a result, they use either sched_yield() or used
> > to use pause() to relinquish the processor so the world could change
> > and they could acquire the locks they wanted.
> 
> The JVM's extensive use of sched_yield(), plus the HT scheduler causes
> some pretty undesirable behaviour in SPECjbb(tm) (see disclaimer).  It
> starves some pieces of the benchmark so badly, that the benchmark
> results are invalid.  We also start to get tons of idle time as the load
> goes up.

Have the Blackdown folks fix that. The Solaris Threads implementation
suppresses the actual call to a yield in the HotSpot VM if it gets too
many of them bunched together in short period of time. It's really a problem
not with the JVM itself, but the Linux implementaion of their threading
glue logic... Make'm fix it. :)

I've heard that a number of folks in Blackdown want to try out the new
threading model, so this might be a good opportunity to do that... add
special thread suspension support, etc...

:)

bill