linux-kernel - [Patch v3 2/3] iommu: optimize iova_magazine_free

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Message-Id: <20191206213803.12580-3-xiyou.wangcong@gmail.com>
Date:   Fri,  6 Dec 2019 13:38:02 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     iommu@...ts.linux-foundation.org
Cc:     linux-kernel@...r.kernel.org, joro@...tes.org,
        Cong Wang <xiyou.wangcong@...il.com>,
        John Garry <john.garry@...wei.com>
Subject: [Patch v3 2/3] iommu: optimize iova_magazine_free_pfns()

If the magazine is empty, iova_magazine_free_pfns() should
be a nop, however it misses the case of mag->size==0. So we
should just call iova_magazine_empty().

This should reduce the contention on iovad->iova_rbtree_lock
a little bit, not much at all.

Cc: Joerg Roedel <joro@...tes.org>
Cc: John Garry <john.garry@...wei.com>
Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
---
 drivers/iommu/iova.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index cb473ddce4cf..184d4c0e20b5 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -797,13 +797,23 @@ static void iova_magazine_free(struct iova_magazine *mag)
 	kfree(mag);
 }
 
+static bool iova_magazine_full(struct iova_magazine *mag)
+{
+	return (mag && mag->size == IOVA_MAG_SIZE);
+}
+
+static bool iova_magazine_empty(struct iova_magazine *mag)
+{
+	return (!mag || mag->size == 0);
+}
+
 static void
 iova_magazine_free_pfns(struct iova_magazine *mag, struct iova_domain *iovad)
 {
 	unsigned long flags;
 	int i;
 
-	if (!mag)
+	if (iova_magazine_empty(mag))
 		return;
 
 	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
@@ -820,16 +830,6 @@ iova_magazine_free_pfns(struct iova_magazine *mag, struct iova_domain *iovad)
 	mag->size = 0;
 }
 
-static bool iova_magazine_full(struct iova_magazine *mag)
-{
-	return (mag && mag->size == IOVA_MAG_SIZE);
-}
-
-static bool iova_magazine_empty(struct iova_magazine *mag)
-{
-	return (!mag || mag->size == 0);
-}
-
 static unsigned long iova_magazine_pop(struct iova_magazine *mag,
 				       unsigned long limit_pfn)
 {
-- 
2.21.0