[Python-Dev] Python 3 optimizations continued... (original) (raw)

stefan brunthaler s.brunthaler at uci.edu
Mon Aug 29 23:05:20 CEST 2011

The question really is whether this is an all-or-nothing deal. If you could identify smaller parts that can be applied independently, interest would be higher. Well, it's not an all-or-nothing deal. In my current architecture, I can selectively enable most of the optimizations as I see fit. The only pre-requisite (in my implementation) is that I have two dispatch loops with a changed instruction format. It is, however, not a technical necessity, just the way I implemented it. Basically, you can choose whatever you like best, and I could extract that part. I am just offering to add all the things that I have done :)

Also, I'd be curious whether your techniques help or hinder a potential integration of a JIT generator. This is something I have previously frequently discussed with several JIT people. IMHO, having my optimizations in-place also helps a JIT compiler, since it can re-use the information I gathered to generate more aggressively optimized native machine code right away (the inline caches can be generated with the type information right away, some functions could be inlined with the guard statements subsumed, etc.) Another benefit could be that the JIT compiler can spend longer time on generating code, because the interpreter is already faster (so in some cases it would probably not make sense to include a non-optimizing fast and simple JIT compiler). There are others on the list, who probably can/want to comment on this, too.

That aside, I think that while having a JIT is an important goal, I can very well imagine scenarios where the additional memory consumption (for the generated native machine code) of a JIT for each process (I assume that the native machine code caches are not shared) hinders scalability. I have in fact no data to back this up, but I think that would be an interesting trade off, say if I have 30% gain in performance without substantial additional memory requirements on my existing hardware, compared to higher achievable speedups that require more machines, though.

Regards, --stefan

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