Mem usage in Mac OSX

[Pierre d'Herbemont]

On 3 oct. 06, at 08:09, Ken Thomases wrote:

> The other really big chunk of VM (after Wine) is labeled as "STACK  
> GUARD".  I believe the intent of STACK GUARD space is to generate  
> exceptions (EXC_BAD_ACCESS / SIGSEGV) if a stack grows beyond its  
> pre-allocated bounds.  It's another 1.5GB!  This seems like the  
> real culprit.  I think STACK GUARD pages should only show up in  
> single-page areas (4K) on either side of a stack.  I'm seeing huge  
> areas (~240MB, ~250MB, and ~1GB).  There's only one actual stack  
> showing.  It's 8MB, between the 250MB guard and the 1GB guard.
>
> Checking a normal Mac app (Mail) shows no such huge STACK GUARD  
> areas -- just a single 4K page below each actual stack.
>
> I have no idea what's creating these huge stack guard areas.

It seems that Wine itself asks for it, see:

vmmap on winemine:
STACK GUARD            8fe70000-90000000 [ 1600K] ---/rwx SM=NUL
STACK GUARD            b0000000-bf800000 [253952K] ---/rwx SM=NUL
STACK GUARD            c0000000-ffe00000 [1046528K] ---/rwx SM=NUL

gdb reports:
(gdb) break mmap if *(int*)($esp+8) == 0xc0000000
(gdb) c
Continuing.

Breakpoint 3, 0x90016cc3 in mmap ()
#0  0x90016cc3 in mmap ()
#1  0x60209503 in try_mmap_fixed (addr=0xc0000000, len=536870912,  
prot=0, flags=4162, fildes=-1, off=0) at mmap.c:177
#2  0x6020994d in reserve_area (addr=0xc0000000, end=0xe0000000) at  
mmap.c:233
#3  0x6020996a in reserve_area (addr=0xc0000000, end=0x0) at mmap.c:283
#4  0x602099ef in mmap_init () at mmap.c:350
#5  0x60208829 in wine_init (argc=2, argv=0xbffff9e8,  
error=0xbffff580 "", error_size=1024) at loader.c:648
#6  0x7bf00f2d in main (argc=2, argv=0xbffff9e8) at main.c:58

Pierre