Hi Robert,
Thanks for a thoughtful email!
> Simply stated, given that it stated clearly in this group that Clojure
> runs, on average, slower than the JVM, is the JVM's high memory-
> utilization a non-issue for the Clojure community as well?
In short: yes.
I'm only bothered by the JVM's memory utilization when I'm trying to
run NetBeans or Eclipse on an anemic laptop, alongside my already
large working set:
PID COMMAND %CPU TIME #TH #PRTS #MREGS RPRVT RSHRD
RSIZE VSIZE
1541 firefox-bi 1.7% 53:36.73 13 203- 1506 474M- 29M
533M- 929M-
786 OmniWeb 1.0% 12:32.08 23 309- 2805 353M- 33M
465M- 924M-
1923 NetNewsWir 0.5% 8:00.11 11 237 1969 176M 29M
194M 618M
0 kernel_tas 3.9% 56:06.45 66 2 578 7852K 0
177M 348M
59 WindowServ 8.1% 23:35.83 5 467 1513 26M+ 141M 157M
+ 616M+
2359 Mail 0.0% 13:18.39 14 324 1113 82M 59M
149M 57
Even so, with 4GB of RAM on my laptop I'm rarely concerned by this --
it's only when I throw VMware into the mix that I start to run out of
free memory.
My company's standard server loadout for new machines is 16GB RAM, and
most older ones are 4-8GB. The app server I use looks like this in top:
6086 110 59 0 199M 155M sleep 13:24 0.05% java
Sure, under load that will increase, but it's still negligible in the
context of available memory (only a few percent). Additionally, in my
experience the memory "profile" of Java server applications is better
than our C++ applications, which typically experience some bloating or
memory leak issues.
I'd take steady-state 300MB memory consumption any day over a startup
at 50MB ending up at 1.4GB after a couple of months' uptime (a
situation I've seen with C++ server applications).
So, in short: if you're on a low-resource machine, running graphical
Java clients: yes, the JVM's memory consumption might concern you, as
will its startup time. If you're using a machine with more memory, or
are building server software where memory consumption is relatively
insignificant, then you're unlikely to spend any time worrying about it.
> Even if CPU performance was good, this
> kind of memory-utilization is unacceptable for application. And that
> is the part that continues to baffle me - what am I missing that so
> many are willing to invest in Clojure and the JVM despite the
> performance characteristics that I have observed.
You're probably baffled because your definition of "unacceptable" is
very different to most using Java SE/EE. The JVM is monolithic
(something Project Jigsaw is trying to fix, precisely to reduce memory
usage in constrained scenarios), but it doesn't bother most people
running Java services on 2008/2009-era servers.
-R
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