linux-kernel - [PATCH v2 RESEND 4/4] staging: ion: optimize struct ion_system

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Date:	Fri, 30 May 2014 10:26:30 +0900
From:	Heesub Shin <heesub.shin@...sung.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	John Stultz <john.stultz@...aro.org>,
	Rebecca Schultz Zavin <rebecca@...roid.com>,
	Colin Cross <ccross@...roid.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	Mitchel Humpherys <mitchelh@...eaurora.org>,
	Daeseok Youn <daeseok.youn@...il.com>,
	Sunghwan Yun <sunghwan.yun@...sung.com>,
	Dongjun Shin <d.j.shin@...sung.com>,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
	Heesub Shin <heesub.shin@...sung.com>
Subject: [PATCH v2 RESEND 4/4] staging: ion: optimize struct ion_system_heap

struct ion_system_heap has an array for storing pointers to page pools
and it is allocated separately from the containing structure. There is
no point in allocating those two small objects individually, bothering
slab allocator. Using a variable length array simplifies code lines and
reduces overhead to the slab.

Signed-off-by: Heesub Shin <heesub.shin@...sung.com>
Reviewed-by: Mitchel Humpherys <mitchelh@...eaurora.org>
Tested-by: John Stultz <john.stultz@...aro.org>
---
 drivers/staging/android/ion/ion_system_heap.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
index e0a7e54..c826b4c 100644
--- a/drivers/staging/android/ion/ion_system_heap.c
+++ b/drivers/staging/android/ion/ion_system_heap.c
@@ -49,7 +49,7 @@ static inline unsigned int order_to_size(int order)
 
 struct ion_system_heap {
 	struct ion_heap heap;
-	struct ion_page_pool **pools;
+	struct ion_page_pool *pools[0];
 };
 
 static struct page *alloc_buffer_page(struct ion_system_heap *heap,
@@ -264,16 +264,15 @@ struct ion_heap *ion_system_heap_create(struct ion_platform_heap *unused)
 	struct ion_system_heap *heap;
 	int i;
 
-	heap = kzalloc(sizeof(struct ion_system_heap), GFP_KERNEL);
+	heap = kzalloc(sizeof(struct ion_system_heap) +
+			sizeof(struct ion_page_pool *) * num_orders,
+			GFP_KERNEL);
 	if (!heap)
 		return ERR_PTR(-ENOMEM);
 	heap->heap.ops = &system_heap_ops;
 	heap->heap.type = ION_HEAP_TYPE_SYSTEM;
 	heap->heap.flags = ION_HEAP_FLAG_DEFER_FREE;
-	heap->pools = kzalloc(sizeof(struct ion_page_pool *) * num_orders,
-			      GFP_KERNEL);
-	if (!heap->pools)
-		goto free_heap;
+
 	for (i = 0; i < num_orders; i++) {
 		struct ion_page_pool *pool;
 		gfp_t gfp_flags = low_order_gfp_flags;
@@ -292,8 +291,6 @@ struct ion_heap *ion_system_heap_create(struct ion_platform_heap *unused)
 destroy_pools:
 	while (i--)
 		ion_page_pool_destroy(heap->pools[i]);
-	kfree(heap->pools);
-free_heap:
 	kfree(heap);
 	return ERR_PTR(-ENOMEM);
 }
-- 
1.9.1

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