From: Pavel Begunkov > Sent: 27 January 2021 15:48 > > On 16/01/2021 05:18, Al Viro wrote: > > On Sat, Jan 09, 2021 at 10:11:09PM +0000, Pavel Begunkov wrote: > > > >>> 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)
