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It does not matter...

It does not matter...

Posted May 22, 2010 9:48 UTC (Sat) by khim (subscriber, #9252)
In reply to: Okay, as far as the interpreters go it's not so bad.... by salimma
Parent article: PyPy: the other new compiler project

You loss can be big or small, but you can't win:

  1. If JIT determines at some point that it's not longer needed and "disconnects" - it's just version of PBO.
  2. If JIT determines that situation is static but checks from time to time that it's not changed - you lose small.
  3. If JIT actively works and changes the recompiles everything all the time - you lose big.

You can only ever win if JIT recompiles stuff constantly (so PBO in normal compiler can't cope) AND the workload does not depend on L1 cache all that much (so loss from JIT work is more then compensated by JIT optimizations). This situation can be easily created in tests but almost never occurs in real life.


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