On Fri, Jan 22, 2021 at 7:47 PM John Stultz <john.stultz@xxxxxxxxxx> wrote:
> +static int system_heap_clear_pages(struct page **pages, int num, pgprot_t pgprot)
> +{
> + void *addr = vmap(pages, num, VM_MAP, pgprot);
> +
> + if (!addr)
> + return -ENOMEM;
> + memset(addr, 0, PAGE_SIZE * num);
> + vunmap(addr);
> + return 0;
> +}
I thought that vmap/vunmap are expensive, and I am wondering if
there's a faster way that avoids vmap.
How about lifting this code from lib/iov_iter.c
static void memzero_page(struct page *page, size_t offset, size_t len)
{
char *addr = kmap_atomic(page);
memset(addr + offset, 0, len);
kunmap_atomic(addr);
}
Or what about lifting that code from the old ion_cma_heap.c
if (PageHighMem(pages)) {
unsigned long nr_clear_pages = nr_pages;
struct page *page = pages;
while (nr_clear_pages > 0) {
void *vaddr = kmap_atomic(page);
memset(vaddr, 0, PAGE_SIZE);
kunmap_atomic(vaddr);
page++;
nr_clear_pages--;
}
} else {
memset(page_address(pages), 0, size);
}
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