From: Pavel Begunkov

Sent: 27 January 2021 15:48

On 16/01/2021 05:18, Al Viro wrote:

quoted

On Sat, Jan 09, 2021 at 10:11:09PM +0000, Pavel Begunkov wrote:

quoted

quoted

Does any code actually look at the fields as a pair?
Would it even be better to use separate bytes?
Even growing the on-stack structure by a word won't really matter.

u8 type, rw;

That won't bloat the struct. I like the idea. If used together compilers
can treat it as u16.

Reasonable, and from what I remember from looking through the users,
no readers will bother with looking at both at the same time.

Al, are you going turn it into a patch, or prefer me to take over?

I'd definitely leave the type as a bitmap.

It may be useful to add ITER_IOVEC_SINGLE to optimise some
very common paths for user iovec with only a single buffer.
But you'd probably want to keep the full version for
more unusual (or already expensive) cases.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)