On 06/19/2017 08:31 AM, Jens Axboe wrote: > 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. Looking at it a bit more closely - there's a difference between assigning X number of streams (allocating) for use by the subsystem or per-ns, and having to manually open them. So I don't necessarily think there's a problem here, neither for us or on the device. If I load the driver as it currently stands, and get streams params after load: Number of Open Streams in NVM subsystem (NOSNS): 0 Allocated Stream Resources (ASR): 4 Number of Open Streams in Namespace (NOSN): 0 4 streams allocated, 0 currently open. Then I generate a single write to some stream ID: Number of Open Streams in NVM subsystem (NOSNS): 1 Allocated Stream Resources (ASR): 4 Number of Open Streams in Namespace (NOSN): 1 and we know see a single stream actually open, implicitly, by the device. Fire off another single stream write, this time to another stream, and we get: Number of Open Streams in NVM subsystem (NOSNS): 2 Allocated Stream Resources (ASR): 4 Number of Open Streams in Namespace (NOSN): 2 and stream status correctly reflects that I did a WRITE_HINT_SHORT and WRITE_HINT_LONG write: Open Stream Count : 2 Stream Identifier 000001 : 1 Stream Identifier 000002 : 3 Awaiting clarification from the vendor what their position/view of this is. Reading the spec, I do agree that it leans towards only needing allocation for a specific name space, but it doesn't explicitly say that you can use any of the available streams, without allocation, if they haven't been assigned to a specific name space. I would interpret it that way, though. -- Jens Axboe
