Re: [PATCH] block: respect virtual boundary mask in bvecs

[Sagi Grimberg]

> > If you mean the real huge page, this patch shouldn't have made a difference
> > because bio_vec->bv_offset is in [0, PAGE_SIZE), and iSer sets virt
> > boundary as 4K - 1.
> >
> > However, things will change after multipage bvec is introduced.
>
>
> Hi Ming,
>
> I've received a blktrace from our customer showing the issue [1].
>
> In this example trace they've submitted (contiguous) 64K I/Os and
> without this patch, they're seeing a lot of splits as indicated by the
> trace.
>
> With the patch applied the I/O is directly issued to the LLDD without
> the splits.
>
> [1] http://beta.suse.com/private/jthumshirn/blktrace.txt

This patch makes sense to me. However I agree that we need to clarify
that this addresses cases where PAGE_SIZE-1 > queue_virt_boundary(q).

And also, lets replace "like iser" with "drivers that sets a virtual
boundary constraint" as nvme-rdma does the same thing.