Re: [RFC PATCH v3 2/3] nvme: keep nvme_command instead of pointer to it

[Kanchan Joshi <joshiiitr@gmail.com>]

On Tue, Mar 16, 2021 at 10:53 PM Keith Busch <kbusch@kernel.org> wrote:
>
> On Tue, Mar 16, 2021 at 07:31:25PM +0530, Kanchan Joshi wrote:
> > nvme_req structure originally contained a pointer to nvme_command.
> > Change nvme_req structure to keep the command itself.
> > This helps in avoiding hot-path memory-allocation for async-passthrough.
>
> I have a slightly different take on how to handle pre-allocated
> passthrough commands. Every transport except PCI already preallocates a
> 'struct nvme_command' within the pdu, so allocating another one looks
> redundant. Also, it does consume quite a bit of memory for something
> that is used only for the passthrough case.
>
> I think we can solve both concerns by always using the PDU nvme_command
> rather than have the transport drivers provide it. I just sent the patch
> here if you can take a look. It tested fine on PCI and loop (haven't
> tested any other transports).
>
>  http://lists.infradead.org/pipermail/linux-nvme/2021-March/023711.html

Sounds fine, thanks for the patch, looking at it.
Which kernel you used for these. 'Patch 2' doesn't  apply cleanly.