On Mon, 31 Aug 1998 14:14:21 +0000, Per Widerlund wrote:
>Hello all!
>
>After reading and hearing about the performance that can
>be gained by using thread pools, I made a simple thread
>pool implementation.
>
>On my Linux machine (PII266/64) running jdk1.1.6-v2 (sbb),
>I got a 0.15 ms/thread reduction in thread start-up overhead.
>(The test was iterated 60000 times.)
I have been doing thread pooling for about as long as I have
been doing Java. The main reason I started (and wrote my own
"thread" class that does the pooling automatically) is so that
the code I had would work. Some of the earlier JDKs had a problem
with leaking memory for each thread created. (Even after all of the
gc() and finalization tricks possible were tried.) This bug has
been fixed in the Sun JDK but some other JVMs do not yet have
this fixed.
>Is a 0.15 ms reduction really worth the effort? A server would
>have to have a very large amount of hits/second before
>0.15 ms makes any difference.
Depends on how you look at it. Most web servers would love to get
that reduction on disk performance. Most web servers are *not* CPU
limited but I/O limited.
Now, however, that 0.15ms is on a Linux system running the current
and reasonably fixed JDK> It is running "greenthreads" which means
that the threads are *very* light weight and implemented at the
JVM. On systems with native threads, the thread overhead may well
be much higher. On my Windows95 box (something no sane person would
use as a server) the thread overhead is such that I saved over 7ms
in thread startup time by using an already existing thread from the
pool. That is a rather large number. On NT, that number was down to
4.5 ms (but the standard deviation was *much* higher, meaning rather
wide ranging results.)
(BTW - on the same systems, under Linux, I got 0.12 MS savings, using
my test, but then systems do differ) (BTW - PII/266/128meg/etc...)
Michael Sinz -- Director of Research & Development, NextBus Inc.
mailto:[EMAIL PROTECTED] --------- http://www.nextbus.com
My place on the web ---> http://www.users.fast.net/~michael_sinz
