On Wed, 2016-04-13 at 17:29 +0100, Robin Murphy wrote:
> Now that we know exactly which page sizes our caller wants to use in the
> given domain, we can restrict higher-order allocation attempts to just
> those sizes, if any, and avoid wasting any time or effort on other sizes
> which offer no benefit. In the same vein, this also lets us accommodate
> a minimum order greater than 0 for special cases.
>
> Signed-off-by: Robin Murphy <robin.mur...@arm.com>
Hi Robin,
Thanks very much for this patch. It works well on our MT8173.
Tested-by: Yong Wu <yong...@mediatek.com>
> ---
>
> Just throwing this out as a quick solo update as I'm still expecting
> discussion on the rest of the series.
>
[...]
> while (count) {
> struct page *page = NULL;
> - int j;
> + unsigned int order_size;
>
> /*
> * Higher-order allocations are a convenience rather
> * than a necessity, hence using __GFP_NORETRY until
> - * falling back to single-page allocations.
> + * falling back to minimum-order allocations.
> */
> - for (order = min_t(unsigned int, order, __fls(count));
> - order > 0; order--) {
> - page = alloc_pages(gfp | __GFP_NORETRY, order);
> + for (order_mask &= (2U << __fls(count)) - 1;
> + order_mask; order_mask &= ~order_size) {
> + unsigned int order = __fls(order_mask);
> +
> + order_size = 1U << order;
> + page = alloc_pages((order_mask - order_size) ?
> + gfp | __GFP_NORETRY : gfp, order);
> if (!page)
> continue;
> - if (PageCompound(page)) {
> - if (!split_huge_page(page))
> - break;
> - __free_pages(page, order);
> - } else {
> + if (!order)
> + break;
I also added this "if" in my old code. I don't know much about
PageCompound and split_page, but from Will's suggestion[1], this "if" is
unnecessary.
[1]:http://lists.linuxfoundation.org/pipermail/iommu/2016-April/016422.html
> + if (!PageCompound(page)) {
> split_page(page, order);
> break;
> + } else if (!split_huge_page(page)) {
> + break;
> }
> + __free_pages(page, order);
> }
> - if (!page)
> - page = alloc_page(gfp);
> if (!page) {
> __iommu_dma_free_pages(pages, i);
> return NULL;
> }
> - j = 1 << order;
> - count -= j;
> - while (j--)
> + count -= order_size;
> + while (order_size--)
> pages[i++] = page++;
> }
[...]
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