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: Colin Cross <ccross@android.com> Signed-off-by: John Stultz <john.stultz@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -100,40 +100,48 @@ int ion_heap_map_user(struct ion_heap *heap, struct ion_buffer *buffer,
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return 0;
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return 0;
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}
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}
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static int ion_heap_clear_pages(struct page **pages, int num, pgprot_t pgprot)
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{
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void *addr = vm_map_ram(pages, num, -1, pgprot);
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if (!addr)
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return -ENOMEM;
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memset(addr, 0, PAGE_SIZE * num);
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vm_unmap_ram(addr, num);
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return 0;
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}
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int ion_heap_buffer_zero(struct ion_buffer *buffer)
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int ion_heap_buffer_zero(struct ion_buffer *buffer)
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{
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{
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struct sg_table *table = buffer->sg_table;
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struct sg_table *table = buffer->sg_table;
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pgprot_t pgprot;
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pgprot_t pgprot;
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struct scatterlist *sg;
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struct scatterlist *sg;
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struct vm_struct *vm_struct;
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int i, j, ret = 0;
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int i, j, ret = 0;
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struct page *pages[32];
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int k = 0;
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if (buffer->flags & ION_FLAG_CACHED)
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if (buffer->flags & ION_FLAG_CACHED)
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pgprot = PAGE_KERNEL;
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pgprot = PAGE_KERNEL;
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else
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else
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pgprot = pgprot_writecombine(PAGE_KERNEL);
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pgprot = pgprot_writecombine(PAGE_KERNEL);
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vm_struct = get_vm_area(PAGE_SIZE, VM_ALLOC);
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if (!vm_struct)
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return -ENOMEM;
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for_each_sg(table->sgl, sg, table->nents, i) {
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for_each_sg(table->sgl, sg, table->nents, i) {
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struct page *page = sg_page(sg);
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struct page *page = sg_page(sg);
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unsigned long len = sg->length;
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unsigned long len = sg->length;
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for (j = 0; j < len / PAGE_SIZE; j++) {
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for (j = 0; j < len / PAGE_SIZE; j++) {
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struct page *sub_page = page + j;
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pages[k++] = page + j;
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struct page **pages = &sub_page;
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if (k == ARRAY_SIZE(pages)) {
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ret = map_vm_area(vm_struct, pgprot, &pages);
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ret = ion_heap_clear_pages(pages, k, pgprot);
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if (ret)
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if (ret)
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goto end;
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goto end;
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memset(vm_struct->addr, 0, PAGE_SIZE);
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k = 0;
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unmap_kernel_range((unsigned long)vm_struct->addr,
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}
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PAGE_SIZE);
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}
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}
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if (k)
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ret = ion_heap_clear_pages(pages, k, pgprot);
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}
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}
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end:
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end:
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free_vm_area(vm_struct);
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return ret;
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return ret;
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}
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}
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