I'd like to get more guidance on how to specify :jvm-opts for maximum
performance. I've received some help on this topic from people on this list in
the past (thanks!), but I'm pretty sure that I'm still not doing things right.
I'm almost always interested in maximum performance for long-running,
compute-intensive and memory-intensive processes, almost never caring much at
all about startup time or anything else.
I also run my code on different machines, with different numbers of cores and
amounts of memory, and would prefer to be able to put something in my
project.clj that will do something reasonable regardless of what machine it's
running on.
I run my code with "lein run", and I'd like whatever I need to "run fast" to be
in project.clj.
I don't know a lot about JVM options, and I've tried to figure out what to
specify for :jvm-opts by asking questions here and web searches, but I'm not at
all confident that I'm doing it right yet. And because my systems are also
stochastic, it's not easy for me to do timing tests on the options I've tried.
I think there are options relevant to memory and also garbage collection and
maybe also compilation... and what else? I wish there was a simple switch to
get maximum performance of the sort I've outlined here (or at least a
reasonable stab at it), but I gather that there isn't.
Anyway, here's what I've been using recently, which just deals with memory and
GC (and maybe not in the best way):
:jvm-opts ~(let [mem-to-use (long (* (.getTotalPhysicalMemorySize
(java.lang.management.ManagementFactory/getOperatingSystemMXBean))
0.8))]
[(str "-Xmx" mem-to-use)
(str "-Xms" mem-to-use)
"-XX:+UseG1GC"])
After seeing Alex's post I thought that maybe I should add "-server", as
follows:
:jvm-opts ~(let [mem-to-use (long (* (.getTotalPhysicalMemorySize
(java.lang.management.ManagementFactory/getOperatingSystemMXBean))
0.8))]
[(str "-Xmx" mem-to-use)
(str "-Xms" mem-to-use)
"-XX:+UseG1GC"
"-server"])
Is that right? Does it make sense? What does "-server" do? Also, should I also
be using "^:replace"?
I've looked in
https://github.com/technomancy/leiningen/blob/master/sample.project.clj in
hopes that this would say more about this stuff, but it doesn't say anything
about -server or ^:replace.
Looking into the compilation options, it looks from
https://github.com/technomancy/leiningen/wiki/Faster that I should be
specifying:
:jvm-opts ^:replace []
This is also familiar to me from some earlier discussions. But how would I
combine this with the memory/GC/server(?) options above?
A guess would be that maybe I should do this:
:jvm-opts ^:replace
~(let [mem-to-use (long (* (.getTotalPhysicalMemorySize
(java.lang.management.ManagementFactory/getOperatingSystemMXBean))
0.8))]
[(str "-Xmx" mem-to-use)
(str "-Xms" mem-to-use)
"-XX:+UseG1GC"
"-server"
"-XX:-TieredCompilation"])
Note that this guess involves changing a + to a - in the last line, which was
suggested for the opposite purpose at
https://github.com/technomancy/leiningen/wiki/Faster -- but I don't know if
it's legitimate.
Is this a reasonable thing to do to get maximum performance for long-running,
compute-intensive and memory-intensive processes?
Is the tiered compilation thing maybe already done by including "-server"?
I'm probably at least somewhat confused about several different issues here...
Any help or pointers would be appreciated.
Thanks,
-Lee
> On May 14, 2015, at 3:47 PM, Alex Miller <a...@puredanger.com> wrote:
>
> Gah. Meant in project.clj:
>
> :jvm-opts ^:replace ["-server"] ;; maybe also set max heap with "-Xmx1g" in
> there
>
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