TranslatedMethods

Ian Piumarta piumarta at prof.inria.fr
Fri Feb 6 11:13:06 UTC 1998


Andreas,

> I noticed that the VM stats in Jitter typically report more translated
> methods than there are CompiledMethods in the image. This has probably
> a very good reason, but could you briefly explain where this is coming
> from?

The VM caches translated methods in the method cache (and inline cache
if enabled).  If the method isn't in either of these caches then the
CompiledMethod is retranslated.  So a single compiled method ends up
having multiple translations.  I measured this once and found that the
average number of translations per CompiledMethod was 8, and that there
was one particular CompiledMethod that had 174 distinct (but identical)
translations.

We (think we) know how to fix this sharing problem fairly easily, but I
haven't had much time to work on it since the release.  (My pay cheques
come from doing something entirely unrelated to Squeak.)  Fixing this is
actually part of a much larger puzzle, and will reduce overheads in
several places.

Regards,

Ian





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