From: Colin Cross <ccross@android.com>
Date: Sat, 14 Dec 2013 03:26:21 +0000 (-0800)
Subject: ion: optimize ion_heap_buffer_zero
X-Git-Tag: v3.14-rc1~150^2~376
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8b312bb9a795c9c07661aee7b694cbfd3217e25c;p=pandora-kernel.git

ion: optimize ion_heap_buffer_zero

ion_heap_buffer_zero can spend a long time in unmap_kernel_range
if it has to broadcast a tlb flush to every cpu for every page.
Modify it to batch pages into a larger region to clear using a
single mapping.  This may cause the mapping size to change if
the buffer size is not a multiple of the mapping size, so
switch to allocating the address space for each chunk.  This
allows us to use vm_map_ram to handle the allocation and mapping
together.

The number of pages to zero using a single mapping is set to 32
to hit the fastpath in vm_map_ram.

Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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