Staging: android: Add lowmemorykiller documentation.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/android/lowmemorykiller.txt

+The lowmemorykiller driver lets user-space specify a set of memory thresholds
+where processes with a range of oom_adj values will get killed. Specify the
+minimum oom_adj values in /sys/module/lowmemorykiller/parameters/adj and the
+number of free pages in /sys/module/lowmemorykiller/parameters/minfree. Both
+files take a comma separated list of numbers in ascending order.
+
+For example, write "0,8" to /sys/module/lowmemorykiller/parameters/adj and
+"1024,4096" to /sys/module/lowmemorykiller/parameters/minfree to kill processes
+with a oom_adj value of 8 or higher when the free memory drops below 4096 pages
+and kill processes with a oom_adj value of 0 or higher when the free memory
+drops below 1024 pages.
+
+The driver considers memory used for caches to be free, but if a large
+percentage of the cached memory is locked this can be very inaccurate
+and processes may not get killed until the normal oom killer is triggered.
+