can we optimize STACK_DEPTH_SLOP

Poking at NetBSD kernel source it looks like the default ulimit -s
depends on the architecture and ranges from 512k to 16M. Postgres
insists on max_stack_depth being STACK_DEPTH_SLOP -- ie 512kB -- less
than the ulimit setting making it impossible to start up on
architectures with a default of 512kB without raising the ulimit.

If we could just lower it to 384kB then Postgres would start up but I
wonder if we should just use MIN(stack_rlimit/2, STACK
_DEPTH_SLOP) so that there's always a setting of max_stack_depth that
would allow Postgres to start.

./arch/sun2/include/vmparam.h:73:#define DFLSSIZ (512*1024) /* initial
stack size limit */
./arch/arm/include/arm32/vmparam.h:66:#define DFLSSIZ (2*1024*1024) /*
initial stack size limit */
./arch/sun3/include/vmparam3.h:109:#define DFLSSIZ (512*1024) /*
initial stack size limit */
./arch/sun3/include/vmparam3x.h:58:#define DFLSSIZ (2*1024*1024) /*
initial stack size limit */
./arch/luna68k/include/vmparam.h:70:#define DFLSSIZ (512*1024) /*
initial stack size limit */
./arch/hppa/include/vmparam.h:62:#define DFLSSIZ (2*1024*1024) /*
initial stack size limit */
./arch/hp300/include/vmparam.h:82:#define DFLSSIZ (2*1024*1024) /*
initial stack size limit */
./arch/alpha/include/vmparam.h:79:#define DFLSSIZ (1<<21) /* initial
stack size (2M) */
./arch/acorn26/include/vmparam.h:55:#define DFLSSIZ (512*1024) /*
initial stack size limit */
./arch/amd64/include/vmparam.h:83:#define DFLSSIZ (4*1024*1024) /*
initial stack size limit */
./arch/amd64/include/vmparam.h:101:#define DFLSSIZ32 (2*1024*1024) /*
initial stack size limit */
./arch/ia64/include/vmparam.h:57:#define DFLSSIZ (1<<21) /* initial
stack size (2M) */
./arch/mvme68k/include/vmparam.h:82:#define DFLSSIZ (512*1024) /*
initial stack size limit */
./arch/i386/include/vmparam.h:74:#define DFLSSIZ (2*1024*1024) /*
initial stack size limit */
./arch/amiga/include/vmparam.h:82:#define DFLSSIZ (2*1024*1024) /*
initial stack size limit */
./arch/sparc/include/vmparam.h:94:#define DFLSSIZ (8*1024*1024) /*
initial stack size limit */
./arch/mips/include/vmparam.h:95:#define DFLSSIZ (4*1024*1024) /*
initial stack size limit */
./arch/mips/include/vmparam.h:114:#define DFLSSIZ (16*1024*1024) /*
initial stack size limit */
./arch/mips/include/vmparam.h:134:#define DFLSSIZ32 DFLTSIZ /* initial
stack size limit */
./arch/sh3/include/vmparam.h:69:#define DFLSSIZ (2 * 1024 * 1024)
./arch/mac68k/include/vmparam.h:115:#define DFLSSIZ (2*1024*1024) /*
initial stack size limit */
./arch/next68k/include/vmparam.h:89:#define DFLSSIZ (512*1024) /*
initial stack size limit */
./arch/news68k/include/vmparam.h:82:#define DFLSSIZ (512*1024) /*
initial stack size limit */
./arch/x68k/include/vmparam.h:74:#define DFLSSIZ (512*1024) /* initial
stack size limit */
./arch/cesfic/include/vmparam.h:82:#define DFLSSIZ (512*1024) /*
initial stack size limit */
./arch/usermode/include/vmparam.h:69:#define DFLSSIZ (2 * 1024 * 1024)
./arch/usermode/include/vmparam.h:78:#define DFLSSIZ (4 * 1024 * 1024)
./arch/powerpc/include/oea/vmparam.h:74:#define DFLSSIZ (2*1024*1024)
/* default stack size */
./arch/powerpc/include/ibm4xx/vmparam.h:60:#define DFLSSIZ
(2*1024*1024) /* default stack size */
./arch/powerpc/include/booke/vmparam.h:75:#define DFLSSIZ
(2*1024*1024) /* default stack size */
./arch/vax/include/vmparam.h:74:#define DFLSSIZ (512*1024) /* initial
stack size limit */
./arch/sparc64/include/vmparam.h:100:#define DFLSSIZ (2*1024*1024) /*
initial stack size limit */
./arch/sparc64/include/vmparam.h:125:#define DFLSSIZ (2*1024*1024) /*
initial stack size limit */
./arch/sparc64/include/vmparam.h:145:#define DFLSSIZ32 (2*1024*1024)
/* initial stack size limit */
./arch/atari/include/vmparam.h:81:#define DFLSSIZ (2*1024*1024) /*
initial stack size limit */


-- 
greg