Martin v. Löwis wrote:
Cameron Laird schrieb:
Folklore that I remember so unreliably I avoid trying to repeat it here held that Python threading had problems on BSD and allied Unixes. What's the status of this?
The problem that people run into again and again is the stack size. The BSDs allow for so little stack so that even the quite conservative estimates of Python as to how many recursions you can have are incorrect, and you get an interpreter crash rather than a RuntimeError (as you should).
There are 2 aspects to the thread stack size issue: - the stack size for the primary thread; - the stack size for created threads. I haven't done any investigating for FreeBSD 6.x and later, but I know that FreeBSD 4.x had a hard coded stack size of 1MB for the primary thread in a thread enabled application, which is what Martin's comment above particularly applies to. This affects code that doesn't use threads at all, and was particularly painful with REs prior to SRE being made non-recursive. If you build the interpreter without thread support, stack space is instead controlled by session limits which are usually generous (typically 64MB). I don't recall exactly FreeBSD's default stack size for threads created via pthread_create() but it is fairly small (32kB or 64kB comes to mind). Zope is one application known to be affected by this lack of stack size in created threads. At least the stack size for new threads can be adjusted at runtime, and a mechanism for doing this was added to Python 2.5.
Furthermore, every time we decrease the that number, the next system release somehow manages to make the limit even smaller. This was never properly analyzed; I suspect that the stack usage of Python increases, either due to compiler changes or due to change to Python itself.
I have seen examples of stack consumption increasing with increasing gcc version number, sometimes depending on optimisation choices. Regards, Andrew. -- ------------------------------------------------------------------------- Andrew I MacIntyre "These thoughts are mine alone..." E-mail: andymac@bullseye.apana.org.au (pref) | Snail: PO Box 370 andymac@pcug.org.au (alt) | Belconnen ACT 2616 Web: http://www.andymac.org/ | Australia