From: Jonas Pfefferle <pepperjo at japf.ch>
To: spdk@lists.01.org
Subject: Re: [SPDK] NVMe command ordering
Date: Fri, 23 Mar 2018 12:59:54 +0100 [thread overview]
Message-ID: <ximss-49410798@switchplus-mail.ch> (raw)
In-Reply-To: CANvN+e=+FDoDj-YYf6H=Oij8AATVGHe_AZOFY=eeY-vbTp_AZg@mail.gmail.com
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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 <= 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
next reply other threads:[~2018-03-23 11:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-23 11:59 Jonas Pfefferle [this message]
-- strict thread matches above, loose matches on Subject: below --
2018-03-27 7:56 [SPDK] NVMe command ordering Jonas Pfefferle
2018-03-24 0:08 Paul Von-Stamwitz
2018-03-23 16:29 Marushak, Nathan
2018-03-23 16:23 Luse, Paul E
2018-03-23 16:21 Jonas Pfefferle
2018-03-23 11:25 Andrey Kuzmin
2018-03-23 9:04 Jonas Pfefferle
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