Date: Mon, 16 Feb 2004 14:00:39 +0000 From: ml@fruitbat.demon.co.uk To: "Brooks Davis" <brooks@one-eyed-alien.net> Cc: freebsd-amd64@freebsd.org Subject: Re: malloc() over 4Gb Message-ID: <E1AsjId-0007tY-0V@anchor-post-31.mail.demon.net> In-Reply-To: <20040126175234.GA28717@Odin.AC.HMC.Edu>
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brooks@one-eyed-alien.net wrote:
> On Sun, Jan 25, 2004 at 01:37:47PM +0000, ml@fruitbat.demon.co.uk wrote:
> > Hi. Could someone clarify whether or not it's possible to malloc()
> > and mmap() chunks of memory > 4Gb in size using FreeBSD/AMD64 and
> > that FreeBSD/AMD64 isn't susceptible to the 4Gb process boundary that
> > 32-bit OSs are restricted by?
>
> It works fine (just remember to set your malloc options to aj before
> mallocing that much memory, it takes a loooong time if you done :-):
> [9:52am] brooks@brimstone (~): uname -a
> FreeBSD brimstone 5.2-CURRENT FreeBSD 5.2-CURRENT #0: Tue Jan 6 13:18:20 P=
> ST 2004 brooks@brimstone:/usr/obj/usr/p4/xname/sys/GENERIC amd64
> [9:52am] brooks@brimstone (~): ./a
> a.out* aeroauth*=20
> [9:52am] brooks@brimstone (~): cat foo.c
> #include <stdio.h>
> #include <stdlib.h>
> #include <stdint.h>
> #define GB (1024*1024*1024)
> int
> main (int argc, char **argv)
> {
> void *foo;
> printf("Trying to malloc %zd bytesn", (size_t)7*GB); foo =3D malloc((size_t)7*GB);
> foo =3D malloc((size_t)7*GB); if (foo !=3D NULL)
> if (foo !=3D NULL)
> printf("Successn"); else
> else
> printf("failuren");}
> }
> [9:52am] brooks@brimstone (~): gcc -o foo foo.c
> [9:52am] brooks@brimstone (~): ./foo=20
> Trying to malloc 7516192768 bytes
> Success
> [9:52am] brooks@brimstone (~):=20
Hi. Thanks for that information!
I went out and bought the box and it does indeed seem to malloc() over
4Gb. However, if you change the allocation from 7*GB to 8*GB in your
sample program, it still keels over inside malloc()!
Do you know if there's any sort of 8Gb clamp in this OS?! Cheers!
> -- Brooks
A.
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