Date: Wed, 23 Nov 2005 11:56:47 -0800 (PST) From: Arne "Wörner" <arne_woerner@yahoo.com> To: Michael Conlen <m@obmail.net> Cc: freebsd-performance@freebsd.org Subject: Re: mmap() Message-ID: <20051123195647.27712.qmail@web30307.mail.mud.yahoo.com> In-Reply-To: <86229116-3E10-4277-B93D-3A9436C2F37A@obmail.net>
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--- Michael Conlen <m@obmail.net> wrote:
> On Nov 23, 2005, at 1:20 PM, Arne Wörner wrote:
> > Maybe the stack size matters in ur case somehow? I can see,
> that
> > it is limited to 1GB, isn't it?
> >
> > I found something funny, too:
> >> limit
> > cputime unlimited
> > filesize unlimited
> > datasize 524288 kbytes
> > stacksize 65536 kbytes
> > coredumpsize unlimited
> > memoryuse unlimited
> > vmemoryuse unlimited
> > descriptors 6861
> > memorylocked unlimited
> > maxproc 3430
> > sbsize unlimited
> >> c++ -o mmap mmap.c
> >> ./mmap 757254143
> > sz2d22c7ff00000 r673435648 errno0
> >> cat mmap.c
> > #include <sys/mman.h>
> > #include <stdio.h>
> > #include <errno.h>
> > #include <stdlib.h>
> >
> > int main(const int argc, char ** argv) {
> > void * r =
> >
>
mmap(0,atoi(argv[argc-1])*1024LL*1024,0,MAP_ANON|MAP_PRIVATE,-1,0);
> > printf("sz%llx r%d
> > errno%d\n",atoi(argv[argc-1])*1024LL*1024,r,errno);
> > return 0;
> > }
> > <EOF>
> >
> > -Arne
> >
>
> At this point I have updated the kernel to include
> 2 GB for stack and data size and edited the
> loader.conf to include those options as well
> with the same result. I really believe the system is
> being limited elsewhere.
>
But why can I get so much memory (722TB) with mmap (even with the
default MAXDSIZ in my kernel)?
Maybe we use mmap(2) the wrong way (I just used it with files: I
found it fancier to write to a file via mmap(2)'ed memory)?
> ./mmap 100
sz6400000 r673435648 errno0
> ./mmap 200
szc800000 r673435648 errno0
> ./mmap 300
sz12c00000 r673435648 errno0
> ./mmap 400
sz19000000 r673435648 errno0
> ./mmap 500
sz1f400000 r673435648 errno0
> ./mmap 600
sz25800000 r673435648 errno0
> ./mmap 700
sz2bc00000 r673435648 errno0
> ./mmap 800
sz32000000 r673435648 errno0
> ./mmap 900
sz38400000 r673435648 errno0
> ./mmap 1024
sz40000000 r673435648 errno0
> ./mmap 710000
szad57000000 r673435648 errno0
> ./mmap 720000
szafc8000000 r-1 errno22
-Arne
P. S.: This reminds me a little bit on the Futurama episode, where
Prof. Farnsworth and his crew travelled back in time to an US army
base, where this funny reporter was unable to get a single clear
and unmorphed photo (he just got a "Nessie"-like pattern and white
spots on black background...)...
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