Messages in this thread | | | Date | Thu, 1 May 2003 04:57:20 -0700 | Subject | Re: must-fix list for 2.6.0 | From | Bill Huey (Hui) <> |
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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
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