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

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Message-ID: <8830b44d-3893-6096-0cf1-37a1e8bc6c6b@huawei.com>
Date:   Fri, 15 Jan 2021 11:32:52 +0000
From:   John Garry <john.garry@...wei.com>
To:     <robin.murphy@....com>, <joro@...tes.org>, <will@...nel.org>
CC:     <xiyou.wangcong@...il.com>, <iommu@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>, <chenxiang66@...ilicon.com>,
        "linuxarm@...neuler.org" <linuxarm@...neuler.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        Kashyap Desai <kashyap.desai@...adcom.com>
Subject: Re: [RESEND PATCH v3 0/4] iommu/iova: Solve longterm IOVA issue

+ linux-scsi (see 
https://lore.kernel.org/linux-iommu/1607538189-237944-4-git-send-email-john.garry@huawei.com/)

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

JFYI, I am able to reproduce this aging issue on another storage card, 
an LSI SAS 3008, so now it's harder to say it's an issue specific to a 
(buggy) single driver.

A log of the IOVA size dumps is here:
https://raw.githubusercontent.com/hisilicon/kernel-dev/064c4dc8869b3f2ad07edffceafde0b129f276b0/lsi3008_dmesg

Notice again how the total IOVA size goes up over time, like:
[ 68.176914] print_iova1 cpu_total=23663 depot_total=256 total=23919
[ 2337.008194] print_iova1 cpu_total=67361 depot_total=9088 total=76449
[17141.860078] print_iova1 cpu_total=73397 depot_total=10368 total=83765
[27087.850830] print_iova1 cpu_total=73386 depot_total=10624 total=84010
[10434.042877] print_iova1 cpu_total=90652 depot_total=12928 total=103580

I had to change some settings for that storage card to reproduce, though 
[0]. Could explain why no other reports.

So please consider this issue again...

Thanks,
john

[0] 
https://lore.kernel.org/linux-scsi/dd8e6fdc-397d-b6ad-3371-0b65d1932ad1@huawei.com/T/#m953d21446a5756981412c92d0924ca65c8d2f3a5

> 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