Re: [Caml-list] concurrent gc?

[Fabrice Le Fessant <Fabrice.Le_fessant@inria.fr>]

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Note that the cost of the GC does not automatically depends on the size of
RAM. In many networking servers, memory is filled with strings, caching
files on disk or content to be sent on the network. Such cases make OCaml
GC happy, since it does not have to manipulate many objects, and it won't
scan strings for pointers within them. There are also other tricks to
improve the GC behavior: you might want to change the data representation
to decrease the number of blocks in the heap, I used to do it a lot when
doing computations on millions of entries that would not otherwise stay in
memory.

--Fabrice


On Thu, Jul 24, 2014 at 8:58 AM, Nicolas Boulay <nicolas@boulay.name> wrote:

> What about server that use ~60GB of RAM ? Todays server are sold with 32
> to 256 GB of RAM and lot of cpu core.
> Maybe in such extreme cases, offloading the major collection of the GC
> could reduce latency a lot ?
>
>
> 2014-07-24 2:05 GMT+02:00 John F. Carr <jfc@mit.edu>:
>
>
>> Most programs spend a minority of their time in garbage collection.
>> Even if the new GC thread did not slow down the main program,
>> possible speedup would be less than 2x, probably well under 50%.
>>
>> For technical reasons, offloading major collections in OCaml is easier
>> than offloading minor collections, so the potential benefit is less.
>>
>>  > extremely clueless question warning, both generally technically but
>>  > also vis-a-vie ocaml specifically:
>>  >
>>  > so even if ocaml can't so easily be made to support multiple threads
>>  > of ocaml code, could the gc be moved off to another thread? so that it
>>  > could run on another core. would that be of any benefit?
>>
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>
>


-- 
Fabrice LE FESSANT
Chercheur en Informatique
INRIA Paris Rocquencourt -- OCamlPro
Programming Languages and Distributed Systems

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