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staging: ion: shrink highmem pages on kswapd

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ION system heap keeps pages in its pool for better performance. When the
system is under memory pressure, slab shrinker calls the callback
registered and then the pages pooled get freed.

When the shrinker is called, it checks gfp_mask and determines whether
the pages from highmem need to be freed or the pages from lowmem.
Usually, slab shrinker is invoked on kswapd context which gfp_mask is
always GFP_KERNEL, so only lowmem pages are released on kswapd context.
This means that highmem pages in the pool are never reclaimed until
direct reclaim occurs. This can be problematic when the page pool holds
excessive amounts of highmem.

For now, the shrinker callback cannot know exactly which zone should be
targeted for reclamation, as enough information are not passed to. Thus,
it makes sense to shrink both lowmem and highmem zone on kswapd context.

Reported-by: Wonseo Choi <wonseo.choi@samsung.com>
Signed-off-by: Heesub Shin <heesub.shin@samsung.com>
Reviewed-by: Mitchel Humpherys <mitchelh@codeaurora.org>
Tested-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Heesub Shin 2014-05-28 15:52:59 +09:00 committed by Greg Kroah-Hartman
parent bdeb9f1c42
commit 0cd2dc4db3
1 changed files with 5 additions and 1 deletions
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6
drivers/staging/android/ion/ion_page_pool.c
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@ -21,6 +21,7 @@
#include <linux/list.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/swap.h>
#include "ion_priv.h"
static void *ion_page_pool_alloc_pages(struct ion_page_pool *pool)
@ -118,7 +119,10 @@ int ion_page_pool_shrink(struct ion_page_pool *pool, gfp_t gfp_mask,
int freed;
bool high;
high = !!(gfp_mask & __GFP_HIGHMEM);
if (current_is_kswapd())
high = 1;
else
high = !!(gfp_mask & __GFP_HIGHMEM);
if (nr_to_scan == 0)
return ion_page_pool_total(pool, high);