Re: maximum memory limit

[Rogier Wolff]

Rik van Riel wrote:
> On Tue, 8 Feb 2000, Lee Chin wrote:
> 
> > Sorry if this is the wrong list, but what is the maximum virtual
> > memory an application can malloc in the latest kernel?
> > 
> > Just doing a (for example) "malloc(1024)" in a loop will max out
> > close to 1GB even though I have 4 GB ram on my system.
> 
> The kernel supports up to 3GB of address space per process.
> The first 900MB can be allocated by brk() and the rest can
> be allocated by mmap().

Another thing to keep in mind is that to allow efficient
allocation/deallocation, there may be some rounding going on. The 2.0
kmalloc would round 1024 to 2048 and therefore waste almost half the
RAM.

> Problem is that libc malloc() appears to use brk() only, so

glibc will use mmap to implement "malloc". libc5 probably uses brk.

> it is limited to 900MB. You can fix that by doing the brk()
> and malloc() yourself, but I think that in the long run the
> glibc people may want to change their malloc implementation
> so that it automatically supports the full 3GB...

			Roger.
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