Re: [PATCH 11/11] nvme: add support for streams and directives

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On 06/19/2017 12:25 AM, Christoph Hellwig wrote:
> On Sat, Jun 17, 2017 at 09:11:30AM -0600, Jens Axboe wrote:
>> I have two samples here, and I just tested, and both of them want it
>> assigned with nsid=0xffffffff or they will fail the writes... So I'd say
>> we're better off ensuring we do allocate them globally.
> 
> That's clearly against the spec.  I'd say go to your vendor and get
> a refund, as we Linux folks (Martin and I) fought for this so that
> we would not have to do the explicit allocations.
> 
> Another quote for from the spec:
> 
> "Streams are opened by the controller when the host issues a write
>  command that specifies a stream identifier that is not currently open.
>  While a stream is open the controller maintains context for that stream
>  (e.g., buffers for associated data). The host may determine the streams 
>  that are open using the Get Status operation."
> 
> And I think this is very important - otherwise you need to either
> allocate the stremas beforehand as your earlier patches (and we take
> away the resources from the 99% of the users not using write life
> hints), or we need the lazy allocation scheme.  And for that to be
> efficient it probably needs to be lazy per-stream allocation.  That's
> why we got the implicit open in after all.

These are just samples, so no refund possible! As you might remember,
I was pretty adamant on not wanting explicit open/close as well, back
in those days. I'll check with the vendor and see what's going on.

-- 
Jens Axboe




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