Re: [PATCH v2 1/2] nvme: Add Arbitration Burst support

[Christoph Hellwig]

On Wed, Jun 24, 2020 at 03:58:54PM +0800, Baolin Wang wrote:
> On Wed, Jun 24, 2020 at 08:52:58AM +0200, Christoph Hellwig wrote:
> > On Wed, Jun 24, 2020 at 02:49:57PM +0800, Baolin Wang wrote:
> > > >From the NVMe spec, "In order to make efficient use of the non-volatile
> > > memory, it is often advantageous to execute multiple commands from a
> > > Submission Queue in parallel. For Submission Queues that are using
> > > weighted round robin with urgent priority class or round robin
> > > arbitration, host software may configure an Arbitration Burst setting".
> > > Thus add Arbitration Burst setting support.
> > 
> > What is the value add of doing this in the kernel?  Wouldn't a nvme-cli
> > subcommand to just set the arbitration burst to the recommended value,
> > either as a saved or current value be both more useful and also cause
> > less kernel bloat?
> 
> Yes, that's another way to configure the RAB, but for some simple and
> frequently-used usage cases, we just want to use the recommanded arbitration
> burst as default without bothering the nvme-cli tool every reset time.

Please look up how saved features work in nvme.