Re: [PATCH v2] Support for write stream IDs

Martin K. Petersen
2015-05-05T21:39:48Z

>>>>> "Jens" == Jens Axboe <axboe@fb.com> writes:

Jens> The kernel patches deal only with ensuring that the stream
Jens> information gets passed down. If the device requires explicit
Jens> stream open/close actions, then that needs to be handled on the
Jens> side.

Well, I'm deeply concerned about that "on the side" thing. I know you're
trying to make a shortcut by only caring about the transport mechanism
and deferring the whole programming model piece of the equation.

I think the latter is hugely important, though. And if we defer the
programming model question then the chances are that we'll be stuck with
something lame in the standards.

The storage vendors appear to think that a handful of stream ids ought
to be enough for anybody. And that IDs are a scarce resource that
they'll hand out for a limited time if you ask nicely.

I think that model is completely broken and also of limited use for
non-NVM types of storage. Sadly it's the same people who are driving the
NVMe and SCSI proposals so they are similar.

My concern is that by adding just enough plumbing to the kernel to allow
the current standards proposals to work then we'll be stuck with them
forever. And I think that would be very unfortunate.

--
Martin K. Petersen Oracle Linux Engineering