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.

Change-Id: I765a42be8e964bfd3e2886d1ca85a29d60c3bb3e
Signed-off-by: Rik van Riel<riel@redhat.com>
Signed-off-by: Colin Cross <ccross@android.com>
CHROMIUM: zsmalloc: add MODULE_LICENSE

It won't load as a module without MODULE_LICENSE.

BUG=chromium-os:32328
TEST=modprobe zsmalloc works with this change

Change-Id: Ic62fe20816e5079d92ce1da6a9d8a9cdbc7a5074
Signed-off-by: Luigi Semenzato <semenzato@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/26627
Reviewed-by: Olof Johansson <olofj@chromium.org>
CHROMIUM: BACKPORT: staging: zsmalloc: Finish conversion to a separate module

Need BACKPORT, rather than UPSTREAM, since it won't apply cleanly because
we had already fixed the MODULE_LICENSE problem.

---original comment:

ZSMALLOC is tristate, but the code has no MODULE_LICENSE and since it
depends on GPL-only symbols it cannot be loaded as a module.  This in
turn breaks zram which now depends on it.  I assume it's meant to be
Dual BSD/GPL like the other z-stuff.

There is also no module_exit, which will make it impossible to unload.
Add the appropriate module_init and module_exit declarations suggested
by comments.

Reported-by: Christian Ohm <chr.ohm@gmx.net>
References: http://bugs.debian.org/677273
Cc: stable@vger.kernel.org # v3.4
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Conflicts:

	drivers/staging/zsmalloc/zsmalloc-main.c

BUG=chromium-os:36829
TEST=extensively tested manually

Change-Id: I82bc7ffffe3007b82601ec71f43873be2059586c
Signed-off-by: Luigi Semenzato <semenzato@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/38998
Reviewed-by: Olof Johansson <olofj@chromium.org>
CHROMIUM: UPSTREAM: staging: zsmalloc: remove x86 dependency

This patch replaces the page table assisted object mapping
method, which has x86 dependencies, with a arch-independent
method that does a simple copy into a temporary per-cpu
buffer.

While a copy seems like it would be worse than mapping the pages,
tests demonstrate the copying is always faster and, in the case of
running inside a KVM guest, roughly 4x faster.

Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

BUG=chromium-os:36829
TEST=extensive manual testing

Change-Id: I8b41c92eb146c5cf0af40682802ba443f7810a0b
Signed-off-by: Luigi Semenzato <semenzato@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/38999
Reviewed-by: Olof Johansson <olofj@chromium.org>
CHROMIUM: UPSTREAM: staging: zram/zcache: swtich Kconfig dependency from X86 to ZSMALLOC

upstream: commit 6e2361720b9da9ec830d407da058ca1827e62b12

This patch switches zcache and zram dependency to ZSMALLOC
rather than X86.  There is no net change since ZSMALLOC
depends on X86, however, this prevent further changes to
these files as zsmalloc dependencies change.

Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

BUG=chromium-os:36829
TEST=compile, verify that zram module is updated and /boot/config is correct

Change-Id: I91f6ed46549fe62a9fe3035063d98beb2f5d966a
Signed-off-by: Luigi Semenzato <semenzato@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/39289
Tested-by: Luigi Semenzato <semenzato@google.com>
Reviewed-by: Sonny Rao <sonnyrao@chromium.org>
Commit-Ready: Luigi Semenzato <semenzato@google.com>
CHROMIUM: zram: fix 32-bit overflow

The 64-bit division operator is not available in 32-bit kernels,
so have to use do_div.

BUG=chromium:245703
TEST=compiled

Change-Id: I44ab763ea9e115cef6212f6524518cf7d9eac8c7
Signed-off-by: Luigi Semenzato <semenzato@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/64695
Reviewed-by: Doug Anderson <dianders@chromium.org>
CHROMIUM: zram: finish fixing 32-bit overflow

Nasty bug.  PAGE_MASK is unsigned, so it extends to 64 bit with zeros.
The first read in the zram block device is done by mkswap, which
tries to read at the end of device.  zram_set_disksize is a side
effect of the first read, so the disk size is now silently changed
from 6GB to 2GB.  The read fails, but mkswap does not complain either:
it finds the size of the device by trial and error and continues.
Swapon detects the mismatch and fails.

BUG=chromium:245703
TEST=ran before and after change with various printks
Signed-off-by: Luigi Semenzato <semenzato@chromium.org>

Change-Id: I01750554964756c2759375df1f14d7bb8b859ccf
Reviewed-on: https://gerrit.chromium.org/gerrit/65752
Tested-by: Luigi Semenzato <semenzato@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Luigi Semenzato <semenzato@chromium.org>