Hi Joerg,
On 2020-09-04 10:37, Joerg Roedel wrote:
Adding Robin.
Did you miss that I've reviewed this already? :)
https://lore.kernel.org/linux-iommu/3afcc7b2-0bfb-b79c-513f-1beb66c5f...@arm.com/
Robin.
On Thu, Aug 27, 2020 at 04:43:54PM +0800, Shaokun Zhang wrote:
From: Yuqi Jin <jiny...@huawei.com>
The performance of the atomic_xchg is better than atomic_cmpxchg because
no comparison is required. While the value of @fq_timer_on can only be 0
or 1. Let's use atomic_xchg instead of atomic_cmpxchg here because we
only need to check that the value changes from 0 to 1 or from 1 to 1.
Cc: Joerg Roedel <j...@8bytes.org>
Signed-off-by: Yuqi Jin <jiny...@huawei.com>
Signed-off-by: Shaokun Zhang <zhangshao...@hisilicon.com>
---
drivers/iommu/iova.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 45a251da5453..30d969a4c5fd 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -579,7 +579,7 @@ void queue_iova(struct iova_domain *iovad,
/* Avoid false sharing as much as possible. */
if (!atomic_read(&iovad->fq_timer_on) &&
- !atomic_cmpxchg(&iovad->fq_timer_on, 0, 1))
+ !atomic_xchg(&iovad->fq_timer_on, 1))
mod_timer(&iovad->fq_timer,
jiffies + msecs_to_jiffies(IOVA_FQ_TIMEOUT));
}
--
2.7.4
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