[LSF/MM/BPF BOF] Userspace command abouts

[Keith Busch]

On Mon, Feb 27, 2023 at 06:28:41PM +0100, Hannes Reinecke wrote:
> On 2/27/23 17:33, Sagi Grimberg wrote:
> > 
> > I'm not up to speed on how CDL is defined, but I'm unclear how CDL at
> > the queue level would cause the host to open more queues?

Because each CDL class would need its own submission queue in that scheme. They
can all share a single completion queue, so this scheme doesn't necassarily
increase the number of interrupt vectors.

> > Another question, does CDL have any relationship with NVMe "Time Limited
> > Error Recovery"? where the host can set a feature for timeout and
> > indicate if the controller should respect it per command?
> > 
> > While this is not a full-blown every queue/command has its own timeout,
> > it could address the original use-case given by Hannes. And it's already
> > there.
> I guess that is the NVMe version of CDLs; can you give me a reference for
> it?

They're not the same. TLER starts timing after a command experiences a
recoverable error, where CDL is an end-to-end timing for all commands.