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Groups > comp.lang.python > #69882

Re: threading

From Sturla Molden <sturla.molden@gmail.com>
Subject Re: threading
Date 2014-04-08 16:37 +0000
References <87d2gsowck.fsf@elektro.pacujo.net>
Newsgroups comp.lang.python
Message-ID <mailman.9027.1396975079.18130.python-list@python.org> (permalink)

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Marko Rauhamaa <marko@pacujo.net> wrote:

> Queues are fine if you hermetically insulate your objects. IOW, you
> group your objects in single-threaded pseudoprocesses that don't make
> any direct method calls to each other. If you do that, you might as well
> use real processes. That way, you can even naturally enforce your
> insulation assumption against accidents.

No, 10,000 processes will not do. First, they use more resources than
threads, at least on Windows. Second, if something fails, you have 10,000
worker processes to kill. You also risk flooding your system with zombies.
So thanks, but no thanks. I would consider a small pool of processes to
utilize all cores on the CPU, though. But each process would have hundreds
or thousands of threads.

.NET AppDomains is an attempt to solve this. Python do not support
AppDomains in the interpreter. It would be nice if it did, though, e.g. a
thread with an isolated interpreter instance (similar to tcl). But
currently the Python interpreter is not designed for that, as it has states
which are lobal to the process, not just the interpreter.

If we insulate objects completely, we must also serialize (pickle) them
before sending them off as messages on a queue. That can be a major
bottleneck. At least it is in numerical computing with Python. Avoiding
serialization is also an important consideration. But IPC itself is very
fast, so the important part is packing a object into a byte string and
unpacking, not the overhead involved in sending it. Unix domain sockets and
Windows named pipes are close to a memcpy in performance, with very little
overhead. Pickle on the other hand is "very slow". Serialization is hard ot
get around if we use processes for multi-core CPUs, but in a pure
multithread design it is not an issue.

Sturla

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Thread

Re: threading Ben Finney <ben+python@benfinney.id.au> - 2014-04-07 13:05 +1000
  Re: threading Roy Smith <roy@panix.com> - 2014-04-06 23:48 -0400
    Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-07 13:56 +1000
      Re: threading Roy Smith <roy@panix.com> - 2014-04-07 08:26 -0400
        Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-07 22:34 +1000
          Re: threading Roy Smith <roy@panix.com> - 2014-04-07 09:22 -0400
            Re: threading Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-04-07 14:41 +0100
            Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-07 16:49 +0300
              Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-08 00:27 +1000
                Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-07 17:51 +0300
                Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-08 01:12 +1000
            Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-08 00:24 +1000
      Re: threading Rick Johnson <rantingrickjohnson@gmail.com> - 2014-04-08 18:09 -0700
        Re: threading "Neil D. Cerutti" <neilc@norwich.edu> - 2014-04-09 09:50 -0400
          Re: threading Rick Johnson <rantingrickjohnson@gmail.com> - 2014-04-09 08:51 -0700
            Re: threading MRAB <python@mrabarnett.plus.com> - 2014-04-09 18:47 +0100
              Re: threading Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-04-10 11:35 +1200
                Re: threading Roy Smith <roy@panix.com> - 2014-04-09 19:53 -0400
                Re: threading Andrew Berg <robotsondrugs@gmail.com> - 2014-04-09 19:02 -0500
                Re: threading Steven D'Aprano <steve@pearwood.info> - 2014-04-10 02:43 +0000
                Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-10 13:08 +1000
                Re: threading Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-04-10 09:23 +0100
                Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-10 19:11 +1000
            Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-10 04:00 +1000
            Re: threading Steven D'Aprano <steve@pearwood.info> - 2014-04-10 03:44 +0000
              Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-10 13:54 +1000
    Re: threading Ben Finney <ben+python@benfinney.id.au> - 2014-04-07 15:22 +1000
    Re: threading Ethan Furman <ethan@stoneleaf.us> - 2014-04-08 11:09 -0700
    Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-08 21:41 +0200
      Re: threading Grant Edwards <invalid@invalid.invalid> - 2014-04-08 20:30 +0000
        Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-09 00:32 +0200
          Re: threading Rustom Mody <rustompmody@gmail.com> - 2014-04-08 19:17 -0700
  Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-07 08:10 +0300
    Re: threading Paul Rubin <no.email@nospam.invalid> - 2014-04-06 22:39 -0700
      Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-07 08:46 +0300
      Re: threading Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-04-07 19:47 -0400
        Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-08 08:19 +0300
          Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-08 10:47 +0000
            Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-08 15:10 +0300
              Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-08 16:37 +0000
                Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-08 20:17 +0300
            Re: threading Roy Smith <roy@panix.com> - 2014-04-08 09:19 -0400
              Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-08 15:44 +0000
                Re: threading Paul Rubin <no.email@nospam.invalid> - 2014-04-08 09:38 -0700
                Re: threading Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-04-09 14:42 +0100
          Re: threading "Frank Millman" <frank@chagford.com> - 2014-04-09 15:23 +0200
            Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-09 16:55 +0300
              Re: threading "Frank Millman" <frank@chagford.com> - 2014-04-09 16:46 +0200
                Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-09 20:31 +0300
                Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-10 03:52 +1000
                Re: threading Mark H Harris <harrismh777@gmail.com> - 2014-04-10 08:29 -0500
                Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-09 19:20 +0000
          Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-09 23:47 +1000
            Re: threading Roy Smith <roy@panix.com> - 2014-04-09 10:44 -0400
          Re: threading "Frank Millman" <frank@chagford.com> - 2014-04-09 16:30 +0200
            Re: threading Roy Smith <roy@panix.com> - 2014-04-09 10:52 -0400
              Re: threading Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-04-10 11:19 +1200
            Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-09 19:48 +0300
          Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-10 00:44 +1000
          Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-09 15:29 +0000
          Re: threading Terry Reedy <tjreedy@udel.edu> - 2014-04-09 12:14 -0400
          Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-10 02:25 +1000
          Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-09 16:32 +0000
          Re: threading Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-04-09 19:44 -0400
          Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-10 11:05 +1000
          Re: threading "Frank Millman" <frank@chagford.com> - 2014-04-10 11:17 +0200
          Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-10 19:40 +1000
          Re: threading "Frank Millman" <frank@chagford.com> - 2014-04-10 13:10 +0200
            Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-10 14:43 +0300
              Re: threading Roy Smith <roy@panix.com> - 2014-04-10 08:56 -0400
              Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-10 15:24 +0000
                Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-10 19:20 +0300
              Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-11 01:32 +1000
                Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-10 19:25 +0300
                Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-11 03:08 +1000
                Re: threading Rustom Mody <rustompmody@gmail.com> - 2014-04-10 11:14 -0700
                Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-10 22:44 +0300
                Re: threading Rustom Mody <rustompmody@gmail.com> - 2014-04-10 13:21 -0700
                Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-10 23:44 +0300
                Re: threading Rustom Mody <rustompmody@gmail.com> - 2014-04-10 22:15 -0700
                Re: threading Rustom Mody <rustompmody@gmail.com> - 2014-04-10 23:50 -0700
                Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-11 18:36 +0300
                Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-12 01:53 +1000
                Re: threading Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-04-11 16:58 +0100
                Re: threading Rustom Mody <rustompmody@gmail.com> - 2014-04-11 11:54 -0700
                Re: threading Marko Rauhamaa <marko@pacujo.net> - 2014-04-11 22:27 +0300
                Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-11 01:51 +0200
                Re: threading Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-04-11 05:35 +0000
                Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-11 09:26 +0000
                Re: threading Roy Smith <roy@panix.com> - 2014-04-11 08:36 -0400
                Re: threading Grant Edwards <invalid@invalid.invalid> - 2014-04-11 16:18 +0000
                Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-11 02:21 +0200
                Re: threading Terry Reedy <tjreedy@udel.edu> - 2014-04-10 20:23 -0400
          Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-10 21:19 +1000
      Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-08 02:06 +0000
        Re: threading alister <alister.nospam.ware@ntlworld.com> - 2014-04-08 11:07 +0000
          Re: threading Roy Smith <roy@panix.com> - 2014-04-08 09:13 -0400
            Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-08 23:23 +1000
              Re: threading alister <alister.nospam.ware@ntlworld.com> - 2014-04-08 14:15 +0000
                Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-08 16:06 +0000
            Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-08 15:40 +0000
              Re: threading Paul Rubin <no.email@nospam.invalid> - 2014-04-08 09:46 -0700
                Re: threading Chris Angelico <rosuav@gmail.com> - 2014-04-09 02:46 +1000
                Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-08 17:17 +0000
          Re: threading Sturla Molden <sturla.molden@gmail.com> - 2014-04-08 15:19 +0000

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