Friday March 30, 2007
Friday March 30, 2007
Tiered Compilation almost live
A few days ago I putback the change that now causes the server jvm (32bit) to be built as tiered. It doesn't actually enable the jvm to run tiered by default but both compilers are present and you can optionally ask for tiered. I'm still having trouble tuning my multi-tiers jvm and I decided that at the very least I ought to see what feedback there was from people adventuresome enough to try the tiered jvm. I expect that there are pathologies and that you may have to tune the thresholds a bit.
It looks like for the current schedule that this will end up in jdk7 build 12 which is still about a week away. If it isn't in b12 it will certainly be in lucky b13.
You can tell if you have the tiered jvm by running -server -version and you'll see something like:
Java HotSpot(TM) Tiered VM (..., mixed mode)
In order to actually get tiered operation you'll have to ask for it via the switch -XX:+TieredCompilation
You may also want to experiment with the compiler thresholds via -XX:CompileThreshold=<nnn> and -XX:Tier2CompileThreshold=<nnn>. Currently the thresholds are 1000/10000. I've found that 1000/35000 works ok for me. I'm curious to see where others find the best tradeoff.