Re: [PATCH] vhost: allow for many vhost user ports

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Thu, Dec 01, 2016 at 04:26:50PM +0100, Jan Wickbom wrote:
>  static int
> -fdset_fill(fd_set *rfset, fd_set *wfset, struct fdset *pfdset)
> +fdset_fill(struct pollfd *rwfds, struct fdset *pfdset)
>  {
>  	struct fdentry *pfdentry;
> -	int i, maxfds = -1;
> -	int num = MAX_FDS;
> -
> -	if (pfdset == NULL)
> -		return -1;
> +	int i;
> +	int num;
>  
> -	for (i = 0; i < num; i++) {
> +	for (i = 0, num = pfdset->num; i < num; i++) {
>  		pfdentry = &pfdset->fd[i];
> -		if (pfdentry->fd != -1) {
> -			int added = 0;
> -			if (pfdentry->rcb && rfset) {
> -				FD_SET(pfdentry->fd, rfset);
> -				added = 1;
> -			}
> -			if (pfdentry->wcb && wfset) {
> -				FD_SET(pfdentry->fd, wfset);
> -				added = 1;
> -			}
> -			if (added)
> -				maxfds = pfdentry->fd < maxfds ?
> -					maxfds : pfdentry->fd;
> +
> +		if (pfdentry->fd < 0) {
> +			/* Hole in the list. Move the last one here */
> +
> +			*pfdentry = pfdset->fd[num - 1];
> +			pfdset->fd[num - 1].fd = -1;
> +			num = fdset_adjust_num(pfdset);
>  		}
> +		rwfds[i].fd = pfdentry->fd;
> +		rwfds[i].events = pfdentry->rcb ? POLLIN : 0;
> +		rwfds[i].events |= pfdentry->wcb ? POLLOUT : 0;

Another thing is we don't have to re-init this rwfds array again
and again. Instead, we could 

- set it up correctly when fdset_add is invoked: set the fd and
  events.

- reset revents when it's been handled at fdset_event_dispatch().

- swap with the last one and shrink the array on fd delete

Could you make a follow up patch for that?

Thanks.

	--yliu