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ion: optimize ion_heap_buffer_zero

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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>
This commit is contained in:
Colin Cross 2013-12-13 19:26:21 -08:00 committed by Greg Kroah-Hartman
parent f0f0676382
commit 8b312bb9a7
1 changed files with 22 additions and 14 deletions
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36
drivers/staging/android/ion/ion_heap.c
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@ -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);
if (ret)
goto end;
memset(vm_struct->addr, 0, PAGE_SIZE);
unmap_kernel_range((unsigned long)vm_struct->addr,
PAGE_SIZE);
pages[k++] = page + j;
if (k == ARRAY_SIZE(pages)) {
ret = ion_heap_clear_pages(pages, k, pgprot);
if (ret)
goto end;
k = 0;
}
}
if (k)
ret = ion_heap_clear_pages(pages, k, pgprot);
}
end:
free_vm_area(vm_struct);
return ret;
}