dontdump.5 (2010 09)

d
dontdump(5) dontdump(5)
(Tunable Kernel Parameters)
NAME
dontdump - defines which classes of kernel memory pages are not dumped when a kernel panic occurs
VALUES
Failsafe
0
Default
0 (Allow the kernel to choose which classes to dump.)
Allowed values
Integer values from
0 to 1024.
The integer value should be the sum of the integer values for the excluded classes as follows:
UNUSED 2 : Unused pages
USERPG 4 : User pages
BCACHE 8 : Buffer cache
KCODE 16 : Kernel text pages
USTACK 32 : Process stack
FSDATA 64 : File-system Metadata
KDDATA 128 : Kernel dynamic data
KSDATA 256 : Kernel static data
SUPERPG 512 : Unused superpage pool
Recommended values
0 (Allow the kernel to choose which classes to dump.)
The value the kernel usually chooses is
30 = UNUSED + USERPG + KCODE + BCACHE. The kernel
chooses these classes because they are not usually useful in debugging kernel problems.
DESCRIPTION
On large systems, the time required to dump system memory when a kernel panic occurs can be excessive
or even prohibitive, depending on how much physical memory is installed in the system. Fast-dump
capabilities controlled by the
dontdump and alwaysdump parameters provide a means for restricting
kernel dumps to specific types of information:
. Unused Physical Memory
. User Process
. Buffer Cache
. Kernel Code
. Process Stack
. File-System Metadata
. Kernel Dynamic Data
. Kernel Static Data
. Unused Superpage Pool
The
crashconf command, and its associated configuration file /etc/rc.config.d/crashconf
,
control which of these memory classes are to be included in the memory dumps associated with a kernel
panic. On rare occasions, the system may panic before crashconf (1M) is run during the boot process. On
those occasions, the configuration can be set using the
alwaysdump and dontdump tunables.
The bit-map value stored in
dontdump specifies which of these memory classes are not to be included in
the memory dumps associated with a kernel panic.
The default value for this parameter is
0. The system determines whether or not to dump classes of
memory based on the type of crash that occurs, in this case.
Note that certain types of system crash, require a full crash dump. Also, the system operator may request
a full crash dump at the time the dump is taken. In either of these cases, a full dump will be performed
regardless of the classes selected using
dontdump.
Who Is Expected to Change This Tunable?
Only HP Field engineers should change the value of this tunable.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1