tree bedf0a9a8b82414f1acc8d01fb3d2013a3d44208
parent 61aafb6b6e40c99983a9fb68efe28b480e1d7b6a
author Rik van Riel <riel@redhat.com> 1314905210 -0400
committer Suren Baghdasaryan <surenb@google.com> 1528127244 +0000

ANDROID: add extra free kbytes tunable

Add a userspace visible knob to tell the VM to keep an extra amount
of memory free, by increasing the gap between each zone's min and
low watermarks.

This is useful for realtime applications that call system
calls and have a bound on the number of allocations that happen
in any short time period.  In this application, extra_free_kbytes
would be left at an amount equal to or larger than than the
maximum number of allocations that happen in any burst.

It may also be useful to reduce the memory use of virtual
machines (temporarily?), in a way that does not cause memory
fragmentation like ballooning does.

[ccross]
Revived for use on old kernels where no other solution exists.
The tunable will be removed on kernels that do better at avoiding
direct reclaim.

[surenb]
Will be reverted as soon as Android framework is reworked to
use upstream-supported watermark_scale_factor instead of
extra_free_kbytes.

Bug: 86445363
Change-Id: I765a42be8e964bfd3e2886d1ca85a29d60c3bb3e
Signed-off-by: Rik van Riel<riel@redhat.com>
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>