Re: Memory accounting in libgc

[Andrew Gaylard <ag@computer.org>]

On 03/12/14 08:57, Mark H Weaver wrote:
> Andy Wingo <wingo@pobox.com> writes:
>
>> How does this affect libgc?
>>
>> First of all, it gives an answer to the question of "how much memory
>> does an object use" -- simply stop the world, mark the heap in two parts
>> (the first time ignoring the object in question, the second time
>> starting from the object), and subtract the live heap size of the former
>> from the latter.  Libgc could do this without too much problem, it seems
>> to me, on objects of any kind.  It would be a little extra code but it
>> could be useful.  Or not?  Dunno.
> This could be generalized to the far more useful question: "How much
> memory does this set of objects use?", although that's a slippery
> question that might better be formulated as "How much memory would be
> freed if this set of objects were no longer needed?".
>
> For example, suppose you have a large data structure that is referenced
> from two small header objects, A and B.  If you ask "How much memory
> does A use?", the answer will be the size of the small header, and ditto
> for B.  Without being able to ask the more general question, there's no
> way to find out how much would be freed by releasing both.
>
>       Mark
Agreed.  In order to build industrial-strength applications in guile, it's
important to be able to answer questions such as "what is causing my
process' memory usage to grow?"

-- 
Andrew Gaylard