Jruby: JRuby with Java 8 4 to 10 times slower than Java 7

[ninkibah]

We are attempting to migrate our Rails 3.2 app to Java 8. It runs fine with JRuby 1.7.9 under Java 6 and Java 7 (Java 7 is a bit faster). However, under Java 8, my tests took 42 minutes elapsed time instead of about 7 minutes. Nobody else seems to have seen this. My colleague has the same issue, and it also happens on a Centos machine we use for testing.

I don't believe it is a problem of memory, as we are giving JAVA 500MB more memory to play with than Java 7.

When we look at execution times of request handling, ActiveRecord (using jdbc-postgres) seems fast but rendering templates takes a very long time. So I suspect String building may be the cause of it.

Versions:
JRuby 1.7.9 or 1.7.13
Java 1.8.0_11 64-Bit Server build 25.11-b03.
Ubuntu 12.04 (Don't know the version of Centos on test machine)
JAVA_OPTS="-Xms512m -Xmx2096m -Djava.net.preferIPv4Stack=true"

Any tips on hunting down the performance problem would be appreciated.

[kwando]

jruby enables invoke dynamic when it detects java 8 and it is dead slow with rails, just disable it.

-Xcompile.invokedynamics=false

[ninkibah]

Hannes, thanks for the tip. My tests now run a little bit quicker than with Java 7.

But, I thought invoke dynamic was going to make Ruby super fast, so how come it doesn't work with Rails code? Too much meta-programming?

[kwando]

I thought it should be superfast too but it is not, see my benchmark in this issue #1569 (I got pretty graphs). I do not really know why it is so painfully slow with rails.. it will get fast eventually but it takes about 25K requests before it is done optimizing...

[ninkibah]

As St. Augustine, who programmed in the 4th Century, used to say: "Lord make me optimized, but not just yet"

[enebo]

An addendum to this issue is that on Java 8 we have indy disabled by default. It can be turned on when it works for you, but for now we have had too many complaints about startup time for Rails applications.

[jcode]

is this still true for recent Java 8 builds? or Rails 4.2?

[kares]

@jcode nope, definitely not the case anymore. if you're seeing any perf. regression on Java 8 open an issue