Re: Overcommitable memory??

From: James Sutherland (jas88@cam.ac.uk)
Date: Sun Mar 19 2000 - 15:15:02 EST


On Fri, 17 Mar 2000 12:43:11 +0000 (GMT), you wrote:

>Hi,
>
>On Tue, 14 Mar 2000 14:32:49 -0300 (BRST), Rik van Riel
><riel@conectiva.com.br> said:
>
>>> Without overcommit that just can not happen. There will be
>>> either a free page of memory or a free page of swap into which
>>> you can swap something else out.
>
>> Without overcommit it can still happen, unless you reserve one
>> page of swap space for every page of data that gets mmap()ed...
>
>Even that doesn't cure things. Think about stack growth.

Quite.

Things become a lot clearer if we stop thinking of it as "overcommit",
and regard it as "demand allocated" instead. malloc() just increases
the upper limit on this area; memory is actually allocated when you
USE the address space you allocated earlier via malloc().

James.

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