linux-kernel - Re: [RESEND PATCH v3 0/4] iommu/iova: Solve longterm IOVA issue

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Message-ID: <d87ceec4-b7a1-c600-3b78-6852f0320ce2@huawei.com>
Date:   Tue, 1 Dec 2020 15:35:02 +0000
From:   John Garry <john.garry@...wei.com>
To:     <robin.murphy@....com>, <joro@...tes.org>, <will@...nel.org>
CC:     <xiyou.wangcong@...il.com>, <linuxarm@...wei.com>,
        <iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>,
        <chenxiang66@...ilicon.com>
Subject: Re: [RESEND PATCH v3 0/4] iommu/iova: Solve longterm IOVA issue

On 17/11/2020 10:25, John Garry wrote:

Hi Will,

Is there any chance that we can get these picked up for 5.11? We've seen 
this issue solved here for a long time.

Or, @Robin, let me know if not happy with this since v1.

BTW, patch #4 has been on the go for ~1 year now, and is a nice small 
optimisation from Cong, which I picked up and already had a RB tag.

Thanks,
John

> This series contains a patch to solve the longterm IOVA issue which
> leizhen originally tried to address at [0].
> 
> A sieved kernel log is at the following, showing periodic dumps of IOVA
> sizes, per CPU and per depot bin, per IOVA size granule:
> https://raw.githubusercontent.com/hisilicon/kernel-dev/topic-iommu-5.10-iova-debug-v3/aging_test
> 
> Notice, for example, the following logs:
> [13175.355584] print_iova1 cpu_total=40135 depot_total=3866 total=44001
> [83483.457858] print_iova1 cpu_total=62532 depot_total=24476 total=87008
> 
> Where total IOVA rcache size has grown from 44K->87K over a long time.
> 
> Along with this patch, I included the following:
> - A smaller helper to clear all IOVAs for a domain
> - Change polarity of the IOVA magazine helpers
> - Small optimisation from Cong Wang included, which was never applied [1].
>    There was some debate of the other patches in that series, but this one
>    is quite straightforward.
> 
> Differnces to v2:
> - Update commit message for patch 3/4
> 
> Differences to v1:
> - Add IOVA clearing helper
> - Add patch to change polarity of mag helpers
> - Avoid logically-redundant extra variable in __iova_rcache_insert()
> 
> [0] https://lore.kernel.org/linux-iommu/20190815121104.29140-3-thunder.leizhen@huawei.com/
> [1] https://lore.kernel.org/linux-iommu/4b74d40a-22d1-af53-fcb6-5d70183705a8@huawei.com/
> 
> Cong Wang (1):
>    iommu: avoid taking iova_rbtree_lock twice
> 
> John Garry (3):
>    iommu/iova: Add free_all_cpu_cached_iovas()
>    iommu/iova: Avoid double-negatives in magazine helpers
>    iommu/iova: Flush CPU rcache for when a depot fills
> 
>   drivers/iommu/iova.c | 66 +++++++++++++++++++++++++-------------------
>   1 file changed, 38 insertions(+), 28 deletions(-)
>