Device Major max and Disk Max in 2.4.x kernel
I have a problem. Trying to write an iostat for Linux (or use an existing one):
Quoted 1 line
From the kernel source:
[/usr/src/linux-2.4.2/include/linux] :) grep DK_MAX *.h kernel_stat.h:#define DK_MAX_MAJOR 16 kernel_stat.h:#define DK_MAX_DISK 16
What to notice: MAJOR and DISK max are 16.
Again, from the kernel source:
[/usr/src/linux-2.4.2/fs/proc] :) grep -15 DK_MAX proc_misc.c <snip>
for (major = 0; major < DK_MAX_MAJOR; major++) {
for (disk = 0; disk < DK_MAX_DISK; disk++) {
int active = kstat.dk_drive[major][disk] +
kstat.dk_drive_rblk[major][disk] +
kstat.dk_drive_wblk[major][disk];
if (active)
len += sprintf(page + len,
"(%u,%u):(%u,%u,%u,%u,%u) ",
major, disk,
kstat.dk_drive[major][disk],
kstat.dk_drive_rio[major][disk],
kstat.dk_drive_rblk[major][disk],
kstat.dk_drive_wio[major][disk],
kstat.dk_drive_wblk[major][disk]
);
}
}What to notice: We are looping up to the DK_MAX_MAJOR and DK_MAX_DISK. What this means is, any major >16 or disk >16 won't be listed in /proc/stat under the "disk_io" section.
Problem. On my system, which I figure is not too uncommon, I have several partitions on two hard drives and a CDROM. They are configured thusly:
# cat /proc/partitions major minor #blocks name 3 0 20094480 hda 3 1 6313513 hda1 3 2 401625 hda2 3 3 13374112 hda3 3 64 4497152 hdb 56 0 45034920 hdi 56 1 22490968 hdi1 56 2 22539195 hdi2
What to notice: I have a drive on /dev/hdi (never mind why, it actually works) that is block major 56. Not only that, my cdrom device on /dev/hdb is block major 3, but minor number 64. I am assuming for disks, minor == disk. Sorry if this is an incorrect assumption.
No stats for /dev/hdi nor /dev/hdb ever show up in /proc/stat. Only for /dev/hda. On my other 2.4.2 system, with multiple hard drives under 16/16, I get multiple devices under /proc/stat.
The patch seems relatively easy. Change linux/include/linux/kernel_stat.h to allow block major up to 56 (in my case... 64 in general???) and disks up to 64 (in my case).
But we might need more than 64 disks on a block major (there are MANY snips in this so-called cut 'n' paste, because I figure you don't want to see them all):
# l /dev/hd* | sort -n brw-rw---- 1 root disk 3, 79 Feb 22 08:57 /dev/hdb15 brw-rw---- 1 root disk 3, 80 Feb 22 08:57 /dev/hdb16 brw-rw---- 1 root disk 22, 79 Feb 22 08:57 /dev/hdd15 brw-rw---- 1 root disk 22, 80 Feb 22 08:57 /dev/hdd16 brw-rw---- 1 root disk 33, 79 Feb 22 08:57 /dev/hdf15 brw-rw---- 1 root disk 33, 80 Feb 22 08:57 /dev/hdf16 brw-rw---- 1 root disk 34, 79 Feb 22 08:57 /dev/hdh15 brw-rw---- 1 root disk 34, 80 Feb 22 08:57 /dev/hdh16 brw-rw---- 1 root disk 56, 126 Mar 25 17:14 /dev/hdj62 brw-rw---- 1 root disk 56, 127 Mar 25 17:14 /dev/hdj63
What to notice: We have disks up to 127. I never see any block major over 64 on my system. The /dev/hdj device isn't used on my system. /dev/hdi and /dev/hdj belong to a Promise RAID controller on a new-ish
ASUS AMD motherboard.
Let me know if I can be of further service. I must bashfully admit that I'm not enough of a guru to recompile my kernel anymore, or I'd tweak the kernel_stat.h file and recompile myself to test this.
This is just hazy recollection, but I think the 2.2.x kernels have the same problem.
--
PhiloVivero
ps -- I'm not subscribed to this list, so if you want me to see replies... please send to email!