Commit 2070f940 authored Sep 21, 2017 by Zhen Lei Committed by Joerg Roedel Sep 27, 2017

iommu/iova: Optimise rbtree searching



Checking the IOVA bounds separately before deciding which direction to
continue the search (if necessary) results in redundantly comparing both
pfns twice each. GCC can already determine that the final comparison op
is redundant and optimise it down to 3 in total, but we can go one
further with a little tweak of the ordering (which makes the intent of
the code that much cleaner as a bonus).

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Zhen Lei <thunder.leizhen@huawei.com>
Tested-by: Nate Watterson <nwatters@codeaurora.org>
[rm: rewrote commit message to clarify]
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

parent e19b205b

drivers/iommu/iova.c

+3 −6

Original line number	Diff line number	Diff line
		@@ -342,15 +342,12 @@ private_find_iova(struct iova_domain *iovad, unsigned long pfn)
		while (node) {
		struct iova *iova = rb_entry(node, struct iova, node);

		/* If pfn falls within iova's range, return iova */
		if ((pfn >= iova->pfn_lo) && (pfn <= iova->pfn_hi)) {
		return iova;
		}

		if (pfn < iova->pfn_lo)
		node = node->rb_left;
		else if (pfn > iova->pfn_lo)
		else if (pfn > iova->pfn_hi)
		node = node->rb_right;
		else
		return iova; /* pfn falls within iova's range */
		}

		return NULL;

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