gpu: ion: Add ion_page_pool.

This patch adds a new utility heaps can use to manage
memory.  In the past we have found it can be very
expensive to manage the caches when allocating memory,
but it is imposible to know whether a previous user of a
given memory allocation had a cached mapping. This patch
adds the ability to store a pool of pages that were
previously used uncached so that cache maintenance
only need be done when growing this pool.  The pool also
contains a shrinker so memory from the pool can be
recovered in low memory conditions.

Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>
[jstultz: modified patch to apply to staging directory]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/drivers/staging/android/ion/ion_priv.h b/drivers/staging/android/ion/ion_priv.h
index 1027ef4c9d16..0707733b7304 100644
--- a/drivers/staging/android/ion/ion_priv.h
+++ b/drivers/staging/android/ion/ion_priv.h
@@ -22,6 +22,8 @@
 #include <linux/mutex.h>
 #include <linux/rbtree.h>
 #include <linux/sched.h>
+#include <linux/shrinker.h>
+#include <linux/types.h>
 
 #include "ion.h"
 
@@ -195,4 +197,46 @@ void ion_carveout_free(struct ion_heap *heap, ion_phys_addr_t addr,
  */
 #define ION_CARVEOUT_ALLOCATE_FAIL -1
 
+/**
+ * functions for creating and destroying a heap pool -- allows you
+ * to keep a pool of pre allocated memory to use from your heap.  Keeping
+ * a pool of memory that is ready for dma, ie any cached mapping have been
+ * invalidated from the cache, provides a significant peformance benefit on
+ * many systems */
+
+/**
+ * struct ion_page_pool - pagepool struct
+ * @count:		number of items in the pool
+ * @items:		list of items
+ * @shrinker:		a shrinker for the items
+ * @mutex:		lock protecting this struct and especially the count
+ *			item list
+ * @alloc:		function to be used to allocate pageory when the pool
+ *			is empty
+ * @free:		function to be used to free pageory back to the system
+ *			when the shrinker fires
+ * @gfp_mask:		gfp_mask to use from alloc
+ * @order:		order of pages in the pool
+ *
+ * Allows you to keep a pool of pre allocated pages to use from your heap.
+ * Keeping a pool of pages that is ready for dma, ie any cached mapping have
+ * been invalidated from the cache, provides a significant peformance benefit
+ * on many systems
+ */
+struct ion_page_pool {
+	int count;
+	struct list_head items;
+	struct shrinker shrinker;
+	struct mutex mutex;
+	void *(*alloc)(struct ion_page_pool *pool);
+	void (*free)(struct ion_page_pool *pool, struct page *page);
+	gfp_t gfp_mask;
+	unsigned int order;
+};
+
+struct ion_page_pool *ion_page_pool_create(gfp_t gfp_mask, unsigned int order);
+void ion_page_pool_destroy(struct ion_page_pool *);
+void *ion_page_pool_alloc(struct ion_page_pool *);
+void ion_page_pool_free(struct ion_page_pool *, struct page *);
+
 #endif /* _ION_PRIV_H */