Operation Manual
/proc/sys/vm/dirty_background_ratio
Maximum percentage of dirty pages until pdush begins to write them. Default is
5%.
/proc/sys/vm/dirty_ratio
When the dirty page exceeds this percentage of the total memory, processes are
forced to write dirty buffers during their time slice instead of continuing to write.
WARNING: Impairment of the Data Integrity
Changes to the pdush daemon settings endanger the data integrity.
Apart from these processes, journaling le systems, like ReiserFS, Ext3, Ext4 and
others write their metadata independently from pdush, which also prevents the hard
disk from spinning down. To avoid this, a special kernel extension has been developed
for mobile devices. To make use of the extension, install the laptop-mode-tools
package and see /usr/src/linux/Documentation/laptops/laptop-mode
.txt for details.
Another important factor is the way active programs behave. For example, good editors
regularly write hidden backups of the currently modied le to the hard disk, causing
the disk to wake up. Features like this can be disabled at the expense of data integrity.
In this connection, the mail daemon postx makes use of the variable
POSTFIX_LAPTOP. If this variable is set to yes, postx accesses the hard disk far
less frequently.
33.4 Troubleshooting
All error messages and alerts are logged in the le /var/log/messages. The fol-
lowing sections cover the most common problems.
Power Management 559