It's a cycle all right, but without some external reference the whole lot should be garbage collected at once. Is any of these objects being referred to from outside the cycle?

It seems that python's cyclic garbage collector has some latency. i.e. objects are not collected at once, but after some time. This means larger memory consumption for unnecessary objects.

For example here is picture from monitoring of my project in production environment before and after the proposed patch.

http://skitch.com/elephantum/dff2m/monik

And one more point: python's cyclic gc doesn't work on objects which has del method defined. It means, that if any of users define del method in RequestHandler subclass then memory would never be freed.

Thanks, I've committed the fix. (locally; I'll push it to github once I've had a chance to do a little testing).

thanks.

BTW. You've mentioned testing more than once in issues and mailing list. I can't find any testing code in tornado/ though. Does it mean that you have test code somewhere outside github?

I don't have test code for tornado itself. I have unittests for an app that uses tornado that exercise some basic functionality, but when I talk about testing I mostly mean running my app with a new version of tornado and poking around in a browser.