kern.maxdsiz "big memory/tuning" questions

Michael Dexter dexter at
Tue Dec 13 16:34:35 PST 2005

Hello, I'm trying to RTFM but the M does not appear to exist.

I am dealing with processes over 512MB in size on 6.0 on x86 and am 
using these loader.conf tunables as suggested by MySQL and other 

kern.maxdsiz="1073741824" # 1GB
kern.dfldsiz="1073741824" # 1GB
kern.maxssiz="134217728" # 128MB

I can glean so far that:

1. You don't want to exceed physical memory with these
2. These are listed in /boot/defaults/loader.conf
3. This is not controlled by sysctls :)
4. 'limits' will show what they are currently set to

However, I am not clear if:

1. It is permitted to use "M" and "G" notation (kern.maxsiz="1G")? - 
some say yes, some say no and I would prefer not risk the system not 

2. Which tunables actually matter beyond kern.maxdsiz? Some say only 
kern.maxdsiz and some suggest all three. 'man tuning' and the 
handbook (~/handbook/configtuning-kernel-limits.html) only goes into 
maxfiles and maxusers. Searches of this list and Google have yeilded 
what you see above.

Could someone please share some wisdom or docs on this matter?

Much appreciated,


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