Re: [PATCH v3 14/15] nvme: Support atomic writes

[John Garry]

On 14/02/2024 08:00, Christoph Hellwig wrote:
> On Tue, Feb 13, 2024 at 02:21:25PM +0000, John Garry wrote:
> > > Please also read through TP4098(a) and look at the MAM field.
> >
> > It's not public, AFAIK.
>
> Oracle is a member, so you can take a look at it easily.  If we need
> it for Linux I can also work with the NVMe Board to release it.

What I really meant was that I prefer not to quote private TPs in public 
domain. I have the doc.

> > And I don't think a feature which allows us to straddle boundaries is too
> > interesting really.
>
> Without MAM=1 NVMe can't support atomic writes larger than
> AWUPF/NAWUPF, which is typically set to the indirection table
> size.  You're leaving a lot of potential unused with that.

atomic_write_unit_max would always be dictated by min of boundary and 
AWUPF/NAWUPF. With MAM=1, we could increase atomic_write_max_bytes - but 
does it really help us? I mean, atomic_write_max_bytes only comes into 
play for merging - do we get much merging for NVMe transports? I am not 
sure.

Thanks,
John