linux-kernel - Re: [Patch v3 0/3] iommu: reduce spinlock contention on fast path

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Message-ID: <5d517a33-2e5a-529c-578c-707ae0a40e88@huawei.com>
Date:   Tue, 10 Dec 2019 14:53:25 +0000
From:   John Garry <john.garry@...wei.com>
To:     Cong Wang <xiyou.wangcong@...il.com>,
        <iommu@...ts.linux-foundation.org>
CC:     <linux-kernel@...r.kernel.org>
Subject: Re: [Patch v3 0/3] iommu: reduce spinlock contention on fast path

On 06/12/2019 21:38, Cong Wang wrote:
> This patchset contains three small optimizations for the global spinlock
> contention in IOVA cache. Our memcache perf test shows this reduced its
> p999 latency down by 45% on AMD when IOMMU is enabled.
> 
> Cong Wang (3):
>    iommu: avoid unnecessary magazine allocations
>    iommu: optimize iova_magazine_free_pfns()
>    iommu: avoid taking iova_rbtree_lock twice
> ---
>   drivers/iommu/iova.c | 75 ++++++++++++++++++++++++++------------------
>   1 file changed, 45 insertions(+), 30 deletions(-)
> 

I retested, and got a ~1.1% gain in throughput for my storage test - 
results here if interested https://pastebin.com/dSQxYpN8

Thanks,
John