Messages in this thread | | | Subject | Re: [PATCH] iommu/iova: Replace cmpxchg with xchg in queue_iova | From | Robin Murphy <> | Date | Fri, 4 Sep 2020 10:58:14 +0100 |
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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-1beb66c5f164@arm.com/
Robin.
> On Thu, Aug 27, 2020 at 04:43:54PM +0800, Shaokun Zhang wrote: >> From: Yuqi Jin <jinyuqi@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 <joro@8bytes.org> >> Signed-off-by: Yuqi Jin <jinyuqi@huawei.com> >> Signed-off-by: Shaokun Zhang <zhangshaokun@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 > _______________________________________________ > iommu mailing list > iommu@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu >
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