Re: [lkp-robot] [fs] 3deb642f0d: will-it-scale.per_process_ops -8.8% regression

Christoph Hellwig
2018-06-22T12:23:45Z

On Fri, Jun 22, 2018 at 01:17:22PM +0100, Al Viro wrote:
> > The problem is that call to sk_busy_loop(), which is going to be indirect
> > no matter what.
>
> if ->f_poll_head is NULL {
> use ->poll
> } else {
> if can ll_poll (checked in ->f_mode)
> call ->ll_poll(), if it returns what we want - we are done
> add to ->f_poll_head
> call ->poll_mask()

What I have for now is slightly different:

if ((events & POLL_BUSY_LOOP) && file->f_op->poll_busy_loop)
file->f_op->poll_busy_loop(file, events);

if (file->f_op->poll) {
return file->f_op->poll(file, pt);
} else if (file_has_poll_mask(file)) {
...
}

returns whatever we want part is something I want to look into
once the basics are done as it probably is non entirely trivial due to
structure of polling in the low-level network protocol.