From: chromatic <[EMAIL PROTECTED]>
Date: Sun, 24 Feb 2008 01:55:20 -0800
Some of our memory problems seem to be strange interactions between
PObjs allocated out of constant pools, garbage collection, and
freezing/thawing PBC (not to mention the interaction of HLLs).
Amen! -- particularly the "strange" part. I suspect that Kea-CL has
been hard hit lately because it may do things differently. Is there
something I should be looking out for?
PObjs allocated out of constant pools persist in memory. They get marked
(sometimes, but not always), but the garbage collector doesn't sweep the
constant pools to recollect them.
This is not normally a problem for most constant PObjs. It's mostly fine
for
strings, and it's fine for PMCs that do not have a special mark() vtable
entry.
PMCs that *do* need a special mark() are troublesome; they may contain
pointers to non-constant PObjs that *do* need live marking, lest they get
swept away during the second half of GC. If these constant PObjs don't get
marked, there's a problem.
Why do constant PMCs ever need to point to non-constant ones? In other
words, why are those pointed-to PObjs not also constant? IIUC, this is
different from any GC system that I've ever heard of. The whole point
of having "pure space" (or whatever you want to call the readonly
constant space) is to avoid having to follow pointers into pure space;
this ought to be unnecessary because pure objects can't keep dynamic
space objects live. If you allow pointers from pure space into the rest
of the heap, then that invariant no longer applies, and you are forced
to trace pure objects just like any other. Am I missing something here?
. . .
I welcome thoughts and especially explanations and help on this. I've been
tracking down these issues off and on for weeks, and in plenty of detail for
most of the past week. Help!
-- c
I wish I understood even a tenth part of Parrot's memory management.
Given that handicap, I'd be happy to help, in whatever way I can, but
I'm afraid it will take a while to get me up to speed.
-- Bob
