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Date:      Fri, 12 Apr 2019 18:37:47 -0600
From:      Warner Losh <imp@bsdimp.com>
To:        "Patrick M. Hausen" <hausen@punkt.de>
Cc:        FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org>
Subject:   Re: NVME aborting outstanding i/o and controller resets
Message-ID:  <CANCZdfr_0xV=QmeTRtQbtvcp3wN0rw4C7KpgrXt3zVpmADwArg@mail.gmail.com>
In-Reply-To: <92DAD65A-9BFE-4294-9066-977F498300A3@punkt.de>
References:  <818CF16A-D71C-47C0-8A1B-35C9D8F68F4E@punkt.de> <CF2365AE-23EA-4F18-9520-C998216155D5@punkt.de> <CANCZdfoPZ9ViQzZ2k8GT5pNw5hjso3rzmYxzU=s%2B3K=ze%2BLZwg@mail.gmail.com> <58E4FC01-D154-42D4-BA0F-EF9A2C60DBF7@punkt.de> <CANCZdfpeZ-MMKB3Sh=3vhsjJcmFkGG7Jq8nW52D5S45PL3menA@mail.gmail.com> <45D98122-7596-4E8A-8A0D-C33E017C1109@punkt.de> <CANCZdfrcnRwqDPXMyT6xNKUZ5nX8x9Fj6DHbCnh%2BQ4mWzx0vGQ@mail.gmail.com> <92DAD65A-9BFE-4294-9066-977F498300A3@punkt.de>

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On Fri, Apr 12, 2019, 1:22 PM Patrick M. Hausen <hausen@punkt.de> wrote:

> Hi Warner,
>
> thanks for taking the time again =E2=80=A6
>
> > OK. This means that whatever I/O workload we've done has caused the NVM=
E
> card to stop responding for 30s, so we reset it.
>
> I figured as much ;-)
>
> > So it's an intel card.
>
> Yes - I already added this info several times. 6 of them, 2.5=E2=80=9C NV=
ME =E2=80=9Edisk
> drives=E2=80=9C.
>

Yea, it was more of a knowing sigh...

> OK. That suggests Intel has a problem with their firmware.
>
> I came across this one:
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D211713
>
> Is it more probable that Intel has got buggy firmware here than that
> =E2=80=9Ewe=E2=80=9C are missing interrupts?
>

More probable bad firmware. One of the things I think that is in HEAD is a
mitigation for this that looks for completed IO on timeout before doing a
reset.

The mainboard is the Supermicro H11SSW-NT. Two NVME drive bays share
> a connector on the mainboard:
>
>         NVMe Ports ( NVMe 0~7, 10, 11, 14, 15)
>
>         The H11SSW-iN/NT has tweleve (12) NVMe ports (2 ports per 1 Slim
> SAS connector) on the motherboard.
>         These ports provide high-speed, low-latency PCI-E 3.0 x4
> connections directly from the CPU to NVMe Solid
>         State (SSD) drives. This greatly increases SSD data- throughput
> performance and significantly reduces PCI-E
>         latency by simplifying driver/software requirements resulting fro=
m
> direct PCI-E interface from the CPU to the NVMe SSD drives.
>
> Is this purely mechanical or do two drives share PCI-E resources? Which
> would explain
> why the problems always come in pairs (nvme6 and nvme7, for example).
>

I'm unfamiliar with this setup, but coming in pairs increases the missed
interrupt theory in my mind. Firmware issues usually don't come in pairs.

This afternoon I set up a system with 4 drives and I was not able to
> reproduce the problem.
> (We just got 3 more machines which happened to have 4 drives each and no
> M.2 directly
> on the mainboard).
> I will change the config to 6 drives like with the two FreeNAS systems in
> our data center.
>
> > [=E2=80=A6 nda(4) ...]
> > I doubt that would have any effect. They both throw as much I/O onto th=
e
> card as possible in the default config.
>
> I found out - yes, just the same.
>

NDA drives with an iosched kernel will be able to rate limit, which may be
useful as a diagnostic tool...

> There's been some minor improvements in -current here. Any chance you
> could experimentally try that with this test? You won't get as many I/O
> abort errors (since we don't print those), and we have a few more
> workarounds for the reset path (though honestly, it's still kinda stinky)=
.
>
> HEAD or RELENG_12, too?
>

HEAD is preferred, but any recent snapshot will do.

Warner

Kind regards,
> Patrick
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>



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