android/lowmemorykiller: Account for total_swapcache_pages

The lowmemorykiller relies on NR_FILE_PAGES when measureing
the amount of reclaimable memory in the system.
However when swap is enabled swap cache pages are counted
in NR_FILE_PAGES, and swap cache pages aren't as reclaimable
in low memory as file cache pages. Therefore a large swap
cache can result in the lowmemorykiller not running and
an OOM occuring.

In order to ensure the lowmemorykiller properly evaluates the
amount of reclaimable memory don't count the swap cache pages.

Change-Id: I38239283e572f814b277c718eaf6be7f92abacbb
Signed-off-by: Liam Mark <lmark@codeaurora.org>
lowmemorykiller: sysfs node and notifications

Create node "/sys/kernel/mm/lowmem_notify/notify_trigger_active",
on which an userspace application can poll for notification when
the number of free physical memory pages in the system falls below
a set threshold. The threshold is set by the new module parameter
"/sys/module/lowmemorykiller/parameters/notify_trigger".
The threshold should be typically set to be higher than the largest
free pages value in /sys/module/lowmemorykiller/parameters/minfree,
so that notification happens before any processes get killed.

Change-Id: Iccb2d1ff699e34b2c22687997e428eec27787b82
Signed-off-by: Bhargav Gurappadi <bhargavg1@codeaurora.org>
android: lowmemorykiller: notify_trigger_active compatibility

Rename the "/sys/kernel/mm/lowmem_notify/notify_trigger_active" sysfs node
to "/sys/kernel/mm/lowmemorykiller/notify_trigger_active" to present the same
interface used by older kernels.

Change-Id: I49533fa005c965f5a4d6bd2f771e0f7ddfb1a8f3
Signed-off-by: Michael Vines <mvines@codeaurora.org>
staging: android: lowmemorykiller: port zram for android and enhanced lmk routine

Change-Id: Ic58b55ce15cd9b8f809817b1310954a53a85b0aa