> From: Rik van Riel <riel@nl.linux.org>
>
> On Tue, 8 Feb 2000, Lee Chin wrote:
>
> > Just to make sure I have this correct, an application can call brk
> > to allocate memory from its heap space for upto 1GB, after which
> > it has to switch to using mmap for the rest. Is this 1GB fixed or
> > will it ever change? (if it does, it might break my application).
>
> IMHO malloc() should switch to mmap() for the rest :)
>
> > >around 900M if the malloc uses sbrk, but more if it uses mmap.
> > >modern libc's will use mmap for large allocations, since unlike
> > >sbrk, mmap can actually free memory back to the OS.
> >
> > Which version of libc has malloc that uses mmap after 1GB?
>
> None, AFAIK. They use mmap() when you malloc() bigger chunks,
> but they don't use it for smaller chunks when you've run out
> of the first 1GB...
This has already been fixed in the latest glibc pre-releases, and the
change will certainly be in glibc-2.1.3. If you are curious, you can
also get the stand-alone ptmalloc release:
http://www.malloc.de/ptmalloc.tar.gz
which has these changes.
When sbrk() fails (e.g. due to the address space limitations discussed
extensively in this thread), an attempt is now made to create a new
arena in anonymously mmap()ed memory where smaller requests, too, can
be serviced.
Now, where do you all buy those huge amounts of memory ? :-)
(still stuck at 128MB myself...)
Regards,
Wolfram.
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This archive was generated by hypermail 2b29 : Tue Feb 15 2000 - 21:00:14 EST