djspiewak

Quick Tips for Fast Code on the JVM

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

addyosmani

Problem: How can we preprocess JavaScript (at build-time or on the server-side) so engines like V8 don't have to spend as much time in Parse? This is a topic that involves generating either bytecode or a bytecode-like-abstraction that an engine would need to accept. For folks that don't know, modern web apps typically spend a lot longer in Parsing & Compiling JS than you may think.

• Yoav: This can particularly be an issue on mobile. Same files getting parsed all the time for users. Theoretically if we moved the parsing work to the server-side, we would have to worry about it less.
• One angle to this problem is we all ship too much JavaScript. That's one perspective. We could also look at preprocessing.
• We've been talking about this topic over the last few weeks a bit with V8. There were three main options proposed.
• 1. Similar to what optimize-js does. Identify IIFEs and mark them as such so the browser and VMs heuristics will catch them and do a better job than today. optimize-js only tackles IIFE bu

kevincennis

Installing V8 on a Mac

Prerequisites

• Install Xcode (Avaliable on the Mac App Store)
• Install Xcode Command Line Tools (Preferences > Downloads)
• Install depot_tools
  • $ git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
  • $ nano ~/.zshrc
  • Add path=('/path/to/depot_tools' $path)

topin27

def foo(s_, i_ = 0):
	strLen = len(s_)
	if strLen == 0:
		return False
	if i_ < 0:
		return False
	if i_ == (strLen / 2 - 1):
		return s_[i_] == s_[strLen - 1 - i_]
	return (s_[i_] == s_[strLen - 1 - i_] and foo(s_, i_ + 1))