From mboxrd@z Thu Jan  1 00:00:00 1970
Content-Type: multipart/mixed; boundary="===============6296931681975395942=="
MIME-Version: 1.0
From: Jonas Pfefferle <pepperjo at japf.ch>
Subject: Re: [SPDK] NVMe command ordering
Date: Fri, 23 Mar 2018 17:21:10 +0100
Message-ID: <ximss-49448565@switchplus-mail.ch>
In-Reply-To: ximss-49410798@switchplus-mail.ch
List-ID: <spdk@lists.01.org>
To: spdk@lists.01.org

--===============6296931681975395942==
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable

One other thing I stumbled upon:
7.1 "There are no ordering restrictions for completions to the host."

Does that mean if, for example, command A and B were executed in order A,B =

they do not have to complete in this order on the CQ?

Thanks,
Jonas

  On Fri, 23 Mar 2018 12:59:54 +0100
  "Jonas Pfefferle" <pepperjo(a)japf.ch> wrote:
> Thanks!
> =

>  On Fri, 23 Mar 2018 11:25:26 +0000
>  Andrey Kuzmin <andrey.v.kuzmin(a)gmail.com> wrote:
>> On Fri, Mar 23, 2018, 12:04 Jonas Pfefferle <pepperjo(a)japf.ch> =

>>wrote:
>> =

>>> Hi @all,
>>>
>>> Can anyone clarify this for me:
>>> NVMe spec 6.3 Command Ordering Requirements
>>> "For all commands which are not part of a fused operation (refer to =

>>>section
>>> 4.10), or for which the write size is greater than AWUN, each =

>>>command is
>>> processed as an independent entity without reference to other =

>>>commands
>>> submitted to the same I/O Submission Queue or to commands submitted =

>>>to
>>> other
>>> I/O Submission Queues"
>>>
>>> So writes <=3D AWUN size are atomic but there is no ordering between =

>>>the
>>> commands, e.g. write command A issued before write command B to the =

>>>same
>>> LBA
>>> can be executed in order AB or BA, the only thing guaranteed is that =

>>>they
>>> are executed atomically? And there is no way to enforce ordering =

>>>except on
>>> the host side?
>>>
>> =

>> Right, that's exactly what the spec says in that same paragraph you =

>>quote
>> above: "If there are ordering requirements between these commands, =

>>host
>> software or the associated application is required to enforce that =

>>ordering
>> above the level of the controller. " (1.3a, P. 179).
>> =

>> Regards,
>> Andrey
>> =

>> =

>>> Regards,
>>> Jonas
>>>
>>>
>>> _______________________________________________
>>> SPDK mailing list
>>> SPDK(a)lists.01.org
>>> https://lists.01.org/mailman/listinfo/spdk
>>>
>> -- =

>> =

>> Regards,
>> Andrey
> =

> =

> _______________________________________________
> SPDK mailing list
> SPDK(a)lists.01.org
> https://lists.01.org/mailman/listinfo/spdk



--===============6296931681975395942==--