Scenes from LA Ruby Conference - 2010 - Threads and Processes

Take Away

Good discussion of the different facilities available to Ruby and the underlying operating system and their tradeoffs.

Introduction

Aman Gupta - Joe Damato - Threads

http://timetobleed.com Joe's blog.

Fundamentals

What is a thread?

A thread is just a set of execution state.

Models

• Green threads
• Native
• Hybrid

Green 1:N

• Lightweight
• Kernel doesn't know they exist
• Implementation is in userland.

Pros

• Create lots cheaply
• Switch them.
• Schedule them however you want.

Cons

• Main one is that these can switch only between a single Ruby process.

Native Threads 1:1

• Kernel knows they exist
• Some user land code.

Pros

• Take advantage of SMP
• Shared memory
• Blocking in one thread doesn't block

Cons

• didn't get

Hybrid Threads (M;N)

Pros

• Take advantage of SMP
• Cheap setup and teardown

Cons

• Need 2 schedulers

Ruby 1.9 and Erlang use hybrid threads

Preemptive Multitasking

• Operating system switches process regardless of process states.

Cooperative Multitasking

• thread gives up voluntarily.

Fibers

Tools

• strace
• google-perf

lsof - "list of open files" - a utility. Can also be used to get a list of open sockets.

strace

trace system calls and signals.

Ruby: SIGVTALRM used

github.com/ice799/matzruby

• heap_stcks branch
• heap_stacks_186 branch

github.com/tmm1/ruby187

• fibers branch