Testing NVME Split BIO

[Andrey Kuzmin]

On Wed, Dec 3, 2014 at 11:02 PM, Sam Bradshaw (sbradshaw)
<sbradshaw at micron.com> wrote:
>
>
>> -----Original Message-----
>> From: Linux-nvme [mailto:linux-nvme-bounces at lists.infradead.org] On
>> Behalf Of Andrey Kuzmin
>> Sent: Wednesday, December 03, 2014 11:27 AM
>> To: Jeffrey Lien
>> Cc: Sam Bradshaw (sbradshaw); linux-nvme at lists.infradead.org
>> Subject: Re: Testing NVME Split BIO
>>
>> Assuming an NVME device/namespace formatted with 4K block size, I'd
>> give a shot to allocating, say, 8K in user-space with memalign (so that
>> my virtual 8K occupy exactly 2 physical pages), and then issuing a 4K
>> write to the respective nvme block device using any offset into the
>> allocated memory you'd like, such as 2K suggested by Sam in that other
>> email.
>> Regards,
>> Andrey
>
> Using this approach, you'll still end up with a virtually contiguous block, which won't be split.

You're right, it will be split at the nvme (PRP construction) level,
and it's not the same as split bio.

Regards,
Andrey