dump_compress_on.5 (2010 09)

d
dump_compress_on(5) dump_compress_on(5)
(Tunable Kernel Parameters)
NAME
dump_compress_on - selects whether the system dumps memory pages compressed or uncompressed
when a kernel panic occurs
VALUES
Failsafe
0
Default
1 (Allow the kernel to decide whether to dump compressed or not based on the system state at the time of
the crash.)
Allowed value
Integer values
0 and 1.
The setting for
dump_compress_on
is used as follows:
0 Dump uncompressed.
1 Dump with compression for speed if possible.
Recommended values
1 (Allow the kernel to choose dump mode.)
The value the kernel usually chooses is 1.
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. Compressed
dump capability results in smaller and faster dumps that will also take lesser time to save over into the
filesystem.
The
crashconf (see crashconf (1M)) command and its associated configuration file
/etc/rc.config.d/crashconf
control the dump compression mode in the memory dumps associ-
ated with a system crash. On rare occasions, the system may crash before
crashconf is run during the
boot process. On those occasions, the configuration set using the dump_compress_on
tunable will be
used.
The default value for this parameter is
1. The system determines whether or not to dump compressed
based on the type of crash that occurs, in this case.
Note that certain types of system crash require an uncompressed crash dump. Also, the system operator
may request an uncompressed crash dump at the time the dump is taken. In either of these cases, an
uncompressed dump will be performed regardless of the mode selected in
dump_compress_on
.
Who Is Expected to Change This Tunable?
Only HP Field engineers should change the value of this tunable.
Restrictions on Changing
Changes to this tunable take effect immediately.
When Should the Tunable Be Turned On?
This tunable should be turned on to dump compressed when there is a system crash.
What Are the Side Effects of Turning the Tunable Off?
In this case, an uncompressed dump is taken always. On large memory machines, an uncompressed
dump take typically three times longer than a compressed dump.
When Should the Tunable Be Turned Off?
The tunable should be turned off if there is a problem with compressed dumps.
What Are the Side Effects of Turning the Tunable On?
The system decides the dump mode based on the type of crash.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1