[gclist] Hotspot slower on first run

Yoo C. Chung wacko@laplace.snu.ac.kr
20 Oct 1999 02:20:08 +0900

Boehm, Hans writes:

> It's also quite possible that this is really an OS issue that the
> JVM can do nothing about.

I think that this is the reason.  The runtime for Hotspot is really
large (a little over 6MB on SPARC), so the OS would take some time
loading the library into RAM.  Once it's loaded, the copy in the RAM
can be reused in further runs.

Our lab had this kind of problem when we tried to zero out RAM before
each JVM invocation while measuring the performance of various JVMs
(in a somewhat misguided attempt to set everything to a pristine
state).  A rather large startup overhead resulted for Hotspot when we
did that, so we don't do that anymore.  (Though we were a bit tempted
to continue doing so, since it skewered the results in favor of our
own research JVM called LaTTe. ;)

Yoo C. Chung <http://laplace.snu.ac.kr/~wacko/>
School of Electrical Engineering, Seoul National University