Re: [PATCH] iov_iter: Add automatic-alloc for ITER_BVEC and use in direct_splice_read()

[Christoph Hellwig]

On Fri, May 19, 2023 at 08:49:18AM +0100, David Howells wrote:
> direct_splice_read() is then modified to make use of this.  This is less
> efficient if we know in advance that we want to allocate the full buffer as
> we can't so easily use bulk allocation, but it does mean in cases where we
> might not want the full buffer (say we hit a hole in DIO), we don't have to
> allocate it.

Can you eplain the workloads we're trying to optimize for here?

To me splice on O_DIRECT is more of a historic accident than an actually
good use case..