mddisk(ramdisk) root system that image size limit ?

[Xinyu Dong]

OS: FreeBSD 6.2-RELEASE
Environment = VMWare (Version 5) and Computer (CPU=Intel P4 2.4G,
Memory=Kingston 1G DDR400, Storage=2G CF)

create a less-than 100MB of image (image for ramdisk, mfs root)
The loader.rc {
    load kernel                        // The kernel used 6.2 GENERIC
    load -t mfs_root /image    // dd if=/dev/zero of=/image bs=1k count=95k
}
above config can boot normal.


create a greater than 100MB of image (image for ramdisk, mfs root)
The loader.rc {
    load kernel                        // The kernel used 6.2 GENERIC
    load -t mfs_root /image    // dd if=/dev/zero of=/image bs=1k count=128k
}
above config can't boot normal, reboot immediately.

create a equal 100MB or equal 99MB of image (image for ramdisk, mfs root)
The loader.rc {
    load kernel                        // The kernel used 6.2 GENERIC
    load -t mfs_root /image    // dd if=/dev/zero of=/image bs=1k count=100k
(or count=99k)
}
above config can't boot normal, kernel panic.

[TEST after system up]

   1. dd if=/dev/zero of=/image bs=1k count=128k
   2. mdconfig -a -t vnode -f /image -u 0
   3. bsdlabel -Bw /dev/md0 auto
   4. newfs /dev/md0a
   5. mount /dev/md0a /mnt

When system up normally: df -h
Filesystem     Size    Used   Avail Capacity  Mounted on
/dev/ad0s1a       23G    1.5G     20G     7%    /
devfs                 1.0K    1.0K      0B   100%    /dev
/dev/md0a      124M    4.0K    114M     0%    /mnt

system not panic.

but config loader.rc, add "load -t mfs_root /image" or "load -t md_image
/image" will panic.
I tried configuring the kernel, change MD_ROOT_SIZE and
MAXDSIZ=(1024UL*1024*1024); MAXSSIZ=(512UL*1024*1024);
DFLDSIZ=(1024UL*1024*1024), panic still.