Garbage Collection and the Ruby Heap

http://timetobleed.com/garbage-collection-slides-from-la-ruby-conference/

by tmm1 • 16 years ago

99 27 16 years ago

timetobleed.com

jakedouglas• 16 years ago

These slides are _ILL_ bro.

munctional3• 16 years ago

Avoiding local slang when writing is also "ill", my brother.

darkhelmetlive• 16 years ago

I always learn so much from you and Damato.

ice7994• 16 years ago

glad you liked the slides.

mrduncan• 16 years ago

Seriously excellent slides.

Any chance of a video of this talk being released? I'd love some commentary from you guys.

ice7994• 16 years ago

yup, it was recorded. not sure when the video will be out, but i'll tweet it or something as soon as i hear.

cullenking• 16 years ago

Was this a slidestack from a bit ago? I remember reading a slidestack of yours a couple months back on the same topic, and found it VERY informative.

In any event, keep up the free education! I've learned alot going through your site. Oh, and thanks for some great ruby libraries!

tmm15• 16 years ago

This a new presentation specifically about the MRI GC, but it covers some of the same tools mentioned in our Debugging Ruby and Threaded Awesome talks

kevingadd• 16 years ago

Very cool, detailed slides.

I think his notes demonstrate how wildly the 'optimal' settings for a scripting runtime can vary based on use case - 500K slots in a slab makes perfect sense for rails, but 10K also makes pretty good sense for running ruby from the command line to execute a tiny script.

One thing that caught my eye - I think according to slide 52, at startup a rails app is using over 3625840 bytes of heap just to represent newline nodes generated from source code? Am I interpreting the data right, or is he just counting the actual nodes and not the RVALUEs attached to them? Kind of funny to think about optimizing memory usage in a rails app by stripping out superfluous newlines.

tmm15• 16 years ago

You're right, there's about 90k NEWLINE nodes on the heap, and at 40 bytes a piece that's taking up about 3.6mb of slots on the heap that could be used by other ruby objects instead.

Unfortunately, removing newlines from your codebase will not help since NODE_NEWLINE is used for separators like semicolons as well.

Ruby 1.9 gets rid of NODE_NEWLINE altogether by adding a NEWLINE flag to the next node instead. A similar patch will be in the next release of REE.

kristianp• 16 years ago

It's a pity memprof doesn't support 32-bit linux yet. I would like to try out the method in the slides on my 32 bit machine.

ice7994• 16 years ago

working on it.

jcnnghm• 16 years ago

If you haven't, tune the garbage collector for rails. By tuning, I was able to improve the performance of my production application by about 60%.

munctional3• 16 years ago

Can you elaborate a bit on this? Did you simply patch the GC? I've seen Evan Weaver's post (http://blog.evanweaver.com/articles/2009/04/09/ruby-gc-tunin...) on it, but that's it.

tmm15• 16 years ago

GC tuning is easy with REE, you can set environment variables to change the behavior of the mark and sweep collector. See slides 50-53 for more info.

jpr• 16 years ago

Ruby is known as the slowest and memoryhungriest language in common use today, is there any reason why people should know how it achieves that? How does this advance the state of the art?

tmm15• 16 years ago

"Now you know, and knowing is half the battle."

FooBarWidget2• 16 years ago

Uh what? Are you saying some like "X has problem Y, why should anybody study problem Y"?

> and memoryhungriest language in common use today

I think you've never heard of Perl.

telemachos• 16 years ago

I didn't realize that Perl was memory intensive compared with Ruby (or other comparable languages more generally).

Any links for that? (Not trolling: I use both Perl and Ruby day to day, and I'm curious. I certainly haven't noticed significant differences in memory usage. Speed certainly - Perl being faster in many cases.)

chuhnk• 16 years ago

Whoa extremely informative slides, thanks for those. Alot of stuff in there I had no idea about. I love learning.

leftnode• 16 years ago

I'm not fluent in Ruby whatsoever, but I think we need more content like this on HN. Incredibly informative and in depth. I probably won't ever learn Ruby in depth, but I love reading about this type of stuff, learned a lot.

Thanks for the link.

ice7994• 16 years ago

thanks, glad you liked the slides.

wingo• 16 years ago

Sigh. Does anyone have a PDF link?

tmm15• 16 years ago

http://dl.dropbox.com/u/635/gc-export.pdf

Garbage Collection and the Ruby Heap

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