[Python-Dev] Unpickling memory usage problem, and a proposed solution (original) (raw)

Collin Winter collinwinter at google.com
Fri Apr 23 20:53:57 CEST 2010

On Fri, Apr 23, 2010 at 11:49 AM, Alexandre Vassalotti <alexandre at peadrop.com> wrote:

On Fri, Apr 23, 2010 at 2:38 PM, Alexandre Vassalotti <alexandre at peadrop.com> wrote:

Collin Winter wrote a simple optimization pass for cPickle in Unladen Swallow [1]. The code reads through the stream and remove all the unnecessary PUTs in-place.

I just noticed the code removes all PUT opcodes, regardless if they are needed or not. So, this code can only be used if there's no GET in the stream (which is unlikely for a large stream). I believe Collin made this trade-off for performance reasons. However, it wouldn't be hard to make the current code to work like pickletools.optimize().

The optimization pass is only run if you don't use any GETs. The optimization is also disabled if you're writing to a file-like object. These tradeoffs were appropriate for the workload I was optimizing against.

Collin Winter

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