Tag: performance

Playing with the new Haskell epoll event library

~ Don Stewart ~ 16 Comments

Bryan and Johan have been working hard on replacing the GHC runtime’s concurrency mechanism based on select, with a new one based on epoll. This should improve scalability of Haskell server code in a number of ways — more connections sec, more concurrent connections, and so on.

You can read about their work in a series of posts:

And you can find the current code for haskell-event on github: http://github.com/tibbe/event

After reading this post, on how epoll-based user land callbacks can outperform general purpose preemptive threads for non-compute bound IO work, I wanted to see what improvements we can hope for from an epoll-based version in Haskell.

The full code, which shows how to set up simple socket event notification using the event lib, is on the Haskell wiki, and will be useful for getting a flavor of the event lib use.

The results:

So while a simple forkIO/accept version, doing Handle and String IO would peak out around 7k req/sec, the epoll based version reached over 15k req/sec.

So that’s useful: good epoll-based event code for Haskell. The next step will be to see the redesign of Control.Concurrent based on epoll being merged into GHC.

Multicore Haskell Now! ACM Reflections | Projections 2009

~ Don Stewart ~ 2 Comments

Here are the

on approaches to multicore programming in Haskell, presented at the ACM Reflections | Projections conference at the University of Illinois.

Abstract

Multicore computers are here: is your programming language ready for it? Haskell is: you can take an off-the-shelf copy of GHC and write high performance parallel programs right now.

If you want to program a parallel machine, a purely functional language such as Haskell is a good choice: purity ensures the language is by-default safe for parallel execution, (whilst traditional imperative languages are by-default unsafe). This foundation has enabled Haskell to become something of a melting pot for high level approaches to concurrent and parallel programming, all available with an industrial strength compiler and language toolchain, available now for mainstream multicore programming.

This talk will introduce the features Haskell provides for writing high level parallel and concurrent programs. In particular we’ll focus on lightweight semi-explicit parallelism, software transactional memory, and nested data parallelism, so you can go to work writing multicore programs in Haskell.

I’d like to thank Michael Ilseman, Sameer Sundresh and Jeff Green for their hospitality during my visit.