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This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Contravariant and Covariant Functors and Variance of Types over their Type Parameters
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Fix Mongodb "soft rlimits" Warning On Mac OS X (Yosemite)
If you are seeing Mongo soft rlimits warnings in your logs, or a WARNING: soft rlimits too low. Number of files is 256, should be at least 1000 when you login to mongo shell via mongo from the commandline, or any mysterious/unexplained mongo connection errors... follow this how-to exactly and it will resolve the issue for you.
PrintCompilation on different versions of HotSpot VM
About PrintCompilation
This note tries to document the output of PrintCompilation flag in HotSpot VM. It was originally intended to be a reply to a blog post on PrintCompilation from Stephen Colebourne. It's kind of grown too big to fit as a reply, so I'm putting it here.
Most of the contents in this note are based on my reading of HotSpot source code from OpenJDK and experimenting with the VM flags; otheres come from HotSpot mailing lists and other reading materials listed in the "References" section.
I was talking to a coworker recently about general techniques that almost always form the core of any effort to write very fast, down-to-the-metal hot path code on the JVM, and they pointed out that there really isn't a particularly good place to go for this information. It occurred to me that, really, I had more or less picked up all of it by word of mouth and experience, and there just aren't any good reference sources on the topic. So… here's my word of mouth.
This is by no means a comprehensive gist. It's also important to understand that the techniques that I outline in here are not 100% absolute either. Performance on the JVM is an incredibly complicated subject, and while there are rules that almost always hold true, the "almost" remains very salient. Also, for many or even most applications, there will be other techniques that I'm not mentioning which will have a greater impact. JMH, Java Flight Recorder, and a good profiler are your very best friend! Mea