Linux vm tuning

Testuota su zen-kernel.

# The percentage of total system memory at which ALL dirty pages must be 
# commited to disk. Writes after this will block until pdflush is done
##echo    24 > /proc/sys/vm/dirty_ratio
# The percentage of total system memory that can be filled with dirty pages
# waiting to be written to disk by pdflush. Triggering this will not block new writes.
##echo     6 > /proc/sys/vm/dirty_background_ratio
# Both can be instead set bytes
echo $((256*1024*1024)) > /proc/sys/vm/dirty_bytes
echo $((64*1024*1024)) > /proc/sys/vm/dirty_background_bytes
# how long something can be in cache before it needs to be written (2300/100=23s)
echo  2300 > /proc/sys/vm/dirty_expire_centisecs 
# how often the kernel wakes up and check to see if work needs to be done
echo   700 > /proc/sys/vm/dirty_writeback_centisecs