Re: [Python-Dev] Documentation about Python's GC, python-dev list messages referenced in Modules/gcmodule.c not reachable anymore
Hi Neil, Hi Tim, Hi Simon, your responsive and valuable answers cleared up most of the open questions and gave a very positive impression to my project leader about the python community and python itself. Thank you very much! I'm trying to get more into the GC implementation before asking more about some still open points. Gregoire ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
[Python-Dev] Documentation about Python's GC, python-dev list messages referenced in Modules/gcmodule.c not reachable anymore
Title: Documentation about Python's GC, python-dev list messages referenced in Modules/gcmodule.c not reachable anymore Hi All, Hi Neil, While searching documentation about Pythons GC and it's behaviour I found references to the python-dev list in ``Modules/gcmodule.c``. But unfortunately the links to the list do not work anymore. May someone give me a hint how to find the messages (2. to 4. below). Is the article (Link 1. below) up to date or were there major changes in the GC strategies since year 2000? http://svn.python.org/projects/python/trunk/Modules/gcmodule.c 1. http://www.arctrix.com/nas/python/gc/ 2. http://www.python.org/pipermail/python-dev/2000-March/003869.html 3. http://www.python.org/pipermail/python-dev/2000-March/004010.html 4. http://www.python.org/pipermail/python-dev/2000-March/004022.html Background Info: We're seriously evaluating Python for use in embedded realtime systems and need some informations about Pythons garbage collector. What we're interested mostly in the runtime behaviour of the GC. The main question is: Does it interrupt the python interpreter to collect stuff or is collecting done more in the background (e.g. just incrementally collecting)? This is an important question for realtime systems with well defined reaction times. Just point me to documentation if available. Gregoire ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Real time behaviour of Pythons memory management; WAS: RE: Documentation about Python's GC,python-dev list messages referenced in Modules/gcmodule.c notreachable anymore
Garbage Collector findings To understand pythons garbage collector better and to get a picture about the runtime behaviour and performance I did some experiments: The attached script allocates a lot of circularly self referencing lists. Then it instantiates a one item list. I tuned the loop counter in such a way that the subsequent instantiation of the one item list triggers the garbage collector. The number of the circularly self referencing objects is around 9. Results (Pentium4 3GHz, Python 2.4.1 on cygwin/Win2k) - gc gen 1) | time msec 2) | unreachable 3) ---+--+ None | 0.000| All 0 | 0.002| All 1 | 0.007| All 2 | 0.065| All None | 0.000| None 0 | 0.001| None 1 | 0.003| None 2 | 0.018| None --> Collecting a self referencing list costs about 0.7 usec (micro seconds) --> Checking a non collectable self ref list costs about 0.2 usec (micro seconds) Legend: 1) the generation the garbage collector has been triggered to collect (None means that GC wasn't triggered) 2) time for instantiating a list with one entry in msec 3) All: All of the circularly self referencing lists were **unreachable** (thus got collected by the gc) None: None of the circularly self referencing lists were **unreachable** (no garbage available to collect) Questions - 1. Am I correct that in a system which instantiates a lot*) of containerish objects without destructing them again the GC may be triggered to evaluate all generations which may be very costy (see above)? 2. In a system where only generation 0 and 1 get evaluated (because not so much object got instantiated without beeing destructed) the costs are relatively low. Correct? *) a lot means here: more than ``threshold0 * threshold1 * threshold2`` objects, Python 2.4 default values are: 700*10*10 = 7 Gregoire P.S.: Interestingely the counters found by experimenting seem to depend on the platform (my platform: Python 2.4.1, cygwin under Win2k, the counters aren't valid for native Python 2.4.2 under Win2k). gctest.py Description: gctest.py ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
