Red Hat ENTERPRISE LINUX 4.5.0 Reference Manual page 107

to as swap space.
The following files are commonly found in the
• — Configures block I/O debugging when enabled. All read/write and block
block_dump
dirtying operations done to files are logged accordingly. This can be useful if diagnosing disk
spin up and spin downs for laptop battery conservation. All output when
enabled can be retrieved via
Tip
If
block_dump
stop the
block_dump
•
dirty_background_ratio
total memory, via a pdflush daemon. The default value is
•
dirty_expire_centisecs
for writeout. Data which has been dirty in-memory for longer than this interval is written out
next time a pdflush daemon wakes up. The default value is
a second.
• — Starts active writeback of dirty data at this percentage of total memory for the
dirty_ratio
generator of dirty data, via pdflush. The default value is
•
dirty_writeback_centisecs
which periodically writes dirty in-memory data out to disk. The default value is
in hundredths of a second.
• — Minimizes the number of times that a hard disk needs to spin up by keeping
laptop_mode
the disk spun down for as long as possible, therefore conserving battery power on laptops.
This increases efficiency by combining all future I/O processes together, reducing the
frequency of spin ups. The default value is
a laptop is used.
This value is controlled automatically by the acpid daemon once a user is notified battery
power is enabled. No user modifications or interactions are necessary if the laptop supports
the ACPI (Advanced Configuration and Power Interface) specification.
For more information, refer to the following installed documentation:
/usr/share/doc/kernel-doc-<version>/Documentation/laptop-mode.txt
•
lower_zone_protection
memory allocation zones. This is effective when utilized with machines configured with
. The default value is
dmesg
is enabled at the same time as kernel debugging, it is prudent to
daemon, as it generates erroneous disk activity caused by
klogd
.
— Starts background writeback of dirty data at this percentage of
— Defines when dirty in-memory data is old enough to be eligible
— Defines the interval between pdflush daemon wakeups,
0
— Determines how aggressive the kernel is in defending lower
directory:
/proc/sys/vm/
.
0
.
10
, expressed in hundredths of
3000
.
40
, but is automatically enabled in case a battery on
/proc/sys/
is
block_dump
, expressed
500
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