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OCaml runtime using too much memory in 64-bit Linux
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Date: 2007-11-14 (17:08)
From: Lionel Elie Mamane <lionel@m...>
Subject: Re: [Caml-list] Re: OCaml runtime using too much memory in 64-bit Linux
On Wed, Nov 14, 2007 at 11:36:16AM -0500, Brian Hurt wrote:
> Stefan Monnier wrote:

>> How about allocating this array of bytes via mmap and then leave it
>> uninitialized (relying on POSIX's guarantee that it's already
>> initialized to zeros)?
>> This way you can easily have a 4GB "dense" table which doesn't use much
>> RAM since most of the 4GB will be mapped (via copy-on-write) to the same
>> "zero page".

> Even on a system like linux, which optimistically allocates memory
> (i.e.  the actually underlying memory isn't allocated until you
> actually touch it), once you read the page, it has to actually exist
> in memory.

This may not be a problem (but only people that know the system
intimately will *know*), it is plausible that the ocaml runtime system
would not read any entry in the table corresponding to a page that is
not allocated. Or maybe not.