Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753822AbdGULmS (ORCPT ); Fri, 21 Jul 2017 07:42:18 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:35248 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750802AbdGULmL (ORCPT ); Fri, 21 Jul 2017 07:42:11 -0400 From: Robin Murphy To: joro@8bytes.org Cc: iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, dwmw2@infradead.org, thunder.leizhen@huawei.com, lorenzo.pieralisi@arm.com, ard.biesheuvel@linaro.org, Jonathan.Cameron@huawei.com, nwatters@codeaurora.org, ray.jui@broadcom.com Subject: [PATCH v2 1/4] iommu/iova: Optimise rbtree searching Date: Fri, 21 Jul 2017 12:41:58 +0100 Message-Id: X-Mailer: git-send-email 2.12.2.dirty In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1486 Lines: 46 From: Zhen Lei 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 Tested-by: Ard Biesheuvel Tested-by: Zhen Lei [rm: rewrote commit message to clarify] Signed-off-by: Robin Murphy --- v2: No change drivers/iommu/iova.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c index 246f14c83944..8f7552dc4e04 100644 --- a/drivers/iommu/iova.c +++ b/drivers/iommu/iova.c @@ -289,15 +289,12 @@ 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; -- 2.12.2.dirty