Heap allocation in the RTS

Ömer Sinan Ağacan omeragacan at gmail.com
Thu Sep 20 09:42:21 UTC 2018

allocateMightFail allocates new nursery blocks as long as you don't hit the
heap limit, so it returns NULL less often than you might think. In particular,
it doesn't return NULL when the nursery is full, instead it allocates a new
block and adds it to the nursery.

I'd do the GC triggering part in Cmm code instead of C code -- I'm not sure if
it's possible to do this in C code. There should be some functions in
PrimOps.cmm that do heap allocation, maybe look there. I'd look for uses of
ALLOC_PRIM. The file HeapStackCheck.cmm may also be helpful (may at least give
an idea of how a GC is triggered).


David Feuer <david.feuer at gmail.com>, 20 Eyl 2018 Per, 12:34 tarihinde
şunu yazdı:
> If it returns NULL, then I need to back off what I'm doing and trigger a GC. How do I do the latter?
> On Thu, Sep 20, 2018, 5:31 AM Ömer Sinan Ağacan <omeragacan at gmail.com> wrote:
>> allocateMightFail does the heap check for you and returns NULL. For the current
>> capability you can use MyCapability() in Cmm and pass the value to the RTS
>> function you're implementing.
>> Ömer
>> David Feuer <david.feuer at gmail.com>, 20 Eyl 2018 Per, 12:26 tarihinde
>> şunu yazdı:
>> >
>> > Aha! Okay. How do I get the current capability to pass to that? I guess I should probably perform a heap check before calling lookupSta bleName for simplicity, at least to start.
>> >
>> > On Thu, Sep 20, 2018, 5:16 AM Ömer Sinan Ağacan <omeragacan at gmail.com> wrote:
>> >>
>> >> Have you seen Storage.c:allocateMightFail ?
>> >>
>> >> Ömer
>> >>
>> >>
>> >> David Feuer <david.feuer at gmail.com>, 20 Eyl 2018 Per, 11:32 tarihinde
>> >> şunu yazdı:
>> >> >
>> >> > I'm working on re-implementing the stable name system. For the new design, it seems much cleaner to allocate stable names in lookupStableName (in rts/StableName.c) rather than in the C-- code that calls it. But I haven't seen RTS code that does heap allocation. Is it possible? If so, how do I do it?
>> >> > _______________________________________________
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