Spare memory

Spare memory

[BT Templeton]

The `refill_memory_reserve' function (in alloc.c) is a no-op if
SYSTEM_MALLOC is defined, so the spare memory is never actually
allocated. Is this intentional?

Also, why doesn't `memory_full' collect garbage immediately when memory
is exhausted? (Currently it sets `memory_full_cons_threshold', which is
checked in `Feval' and `Ffuncall'.)

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Re: Spare memory

[Stefan Monnier]

> The `refill_memory_reserve' function (in alloc.c) is a no-op if
> SYSTEM_MALLOC is defined, so the spare memory is never actually
> allocated. Is this intentional?

I do not really understand enough about the way we try to handle
out-of-memory situations to be able to answer.

> Also, why doesn't `memory_full' collect garbage immediately when memory
> is exhausted? (Currently it sets `memory_full_cons_threshold', which is
> checked in `Feval' and `Ffuncall'.)

But I can answer this one: the GC can only be called at a few safe
points, so calling it from memory_full might be unsafe.  With the
conservative stack scanning, we can probably safely run the GC in many
more cases, but when using the GCPROs, the only safe spots are when
`eval' can be called.


        Stefan

Re: Spare memory

[Andreas Schwab]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> But I can answer this one: the GC can only be called at a few safe
> points, so calling it from memory_full might be unsafe.  With the
> conservative stack scanning, we can probably safely run the GC in many
> more cases, but when using the GCPROs, the only safe spots are when
> `eval' can be called.

Even without GCPRO it may be unsafe, since GC can compact strings.

Andreas.

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