Re: [PATCH net-next v2 10/17] nvme: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage

[Sagi Grimberg]

> > >      struct bio_vec bvec;
> > >      struct msghdr msg = { .msg_flags = MSG_SPLICE_PAGES | ... };
> > >
> > >      ..
> > >
> > >      bvec_set_virt
> > >      iov_iter_bvec
> > >      sock_sendmsg
> > >
> > > is a frequent pattern. Does it make sense to define a wrapper? Same 
> > > for bvec_set_page.
> >
> > I dunno.  I'm trying to move towards aggregating multiple pages in a bvec
> > before calling sendmsg if possible rather than doing it one page at a 
> > time,
> > but it's easier and more obvious in some places than others.
>
> That would be great to do, but nvme needs to calculate a data digest
> and doing that in a separate scan of the payload is not very cache
> friendly...
>
> There is also the fact that the payload may be sent in portions 
> asynchronously driven by how the controller wants to accept them,
> so there is some complexity there.
>
> But worth looking at for sure.
>
> The patch looks good to me, taking it to run some tests
> (from sendpage-3-frag branch in your kernel.org tree correct?)
>
> For now, you can add:
> Reviewed-by: Sagi Grimberg <sagi@xxxxxxxxxxx>

Patches seem to hold up.
Tested-by: Sagi Grimberg <sagi@xxxxxxxxxxx>

However if possible, can you please split nvme/host and nvme/target
changes? We try to separate host side and target side changes in the
same patch.