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Commit 8b312bb9 authored by Colin Cross's avatar Colin Cross Committed by Greg Kroah-Hartman
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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: default avatarColin Cross <ccross@android.com>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f0f06763

drivers/staging/android/ion/ion_heap.c

+22 −14
Original line number Diff line number Diff line
@@ -100,40 +100,48 @@ int ion_heap_map_user(struct ion_heap *heap, struct ion_buffer *buffer, 
	return 0;

}



static int ion_heap_clear_pages(struct page **pages, int num, pgprot_t pgprot)

{

	void *addr = vm_map_ram(pages, num, -1, pgprot);

	if (!addr)

		return -ENOMEM;

	memset(addr, 0, PAGE_SIZE * num);

	vm_unmap_ram(addr, num);



	return 0;

}



int ion_heap_buffer_zero(struct ion_buffer *buffer)

{

	struct sg_table *table = buffer->sg_table;

	pgprot_t pgprot;

	struct scatterlist *sg;

	struct vm_struct *vm_struct;

	int i, j, ret = 0;

	struct page *pages[32];

	int k = 0;



	if (buffer->flags & ION_FLAG_CACHED)

		pgprot = PAGE_KERNEL;

	else

		pgprot = pgprot_writecombine(PAGE_KERNEL);



	vm_struct = get_vm_area(PAGE_SIZE, VM_ALLOC);

	if (!vm_struct)

		return -ENOMEM;



	for_each_sg(table->sgl, sg, table->nents, i) {

		struct page *page = sg_page(sg);

		unsigned long len = sg->length;



		for (j = 0; j < len / PAGE_SIZE; j++) {

			struct page *sub_page = page + j;

			struct page **pages = &sub_page;

			ret = map_vm_area(vm_struct, pgprot, &pages);

			pages[k++] = page + j;

			if (k == ARRAY_SIZE(pages)) {

				ret = ion_heap_clear_pages(pages, k, pgprot);

				if (ret)

					goto end;

			memset(vm_struct->addr, 0, PAGE_SIZE);

			unmap_kernel_range((unsigned long)vm_struct->addr,

					   PAGE_SIZE);

				k = 0;

			}

		}

		if (k)

			ret = ion_heap_clear_pages(pages, k, pgprot);

	}

end:

	free_vm_area(vm_struct);

	return ret;

}