Re: [dpdk-dev] [PATCH v4] vhost: allow for many vhost user ports

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

On Tue, Dec 13, 2016 at 02:19:47PM +0100, Jan Wickbom wrote:
> +
> +		poll(pfdset->rwfds, numfds, 1000 /* millisecs */);
> +
> +		for (i = 0; i < numfds; ) {
>  			pthread_mutex_lock(&pfdset->fd_mutex);
> +
>  			pfdentry = &pfdset->fd[i];
>  			fd = pfdentry->fd;
> +			pfd = &pfdset->rwfds[i];
> +
> +			if (fd < 0) {
> +				/* Removed during poll */
> +				/* shrink first, last migth be deleted*/
> +
> +				fdset_shrink(pfdset);
> +				fdset_move_last(pfdset, i);
> +				fdset_shrink(pfdset);
> +
> +				pthread_mutex_unlock(&pfdset->fd_mutex);

This patch looks better, but as said, I will not do shrink in the
event processing loop: I would simply set a flag, something like
"need_shrink" here, and do the shrink outside this for loop.


> +			if (remove1 || remove2) {
> +				pthread_mutex_lock(&pfdset->fd_mutex);
> +
> +				/* shrink first, last migth be deleted*/
> +				fdset_shrink(pfdset);
> +				fdset_move_last(pfdset, i);
> +				fdset_shrink(pfdset);
> +
> +				pthread_mutex_unlock(&pfdset->fd_mutex);
> +
> +				continue;

Same here: just sets a flag.

> +			}
> +
> +			i++;
>  		}
> +
> +		/* fdset_del do not shrink, pack eventual remainings of array */
> +		pthread_mutex_lock(&pfdset->fd_mutex);
> +
> +		fdset_shrink(pfdset);
> +
> +		for ( ; i < pfdset->num; i++) {
> +			pfdentry = &pfdset->fd[i];
> +
> +			if (pfdentry->fd < 0) {
> +				fdset_move_last(pfdset, i);
> +				fdset_shrink(pfdset);
> +			}
> +		}

And yes, do the shrink here (when the shrink flag is set). But I would
simply call fdset_shrink() here (without the for loop), and let the
fdset_shrink() to handle the details: it could either be a swap with
last __valid__ entry, or simply a memmov.

That said, if you prefer to choose fdset_move_last(), fine, invoke it
inside fdset_shrink() then. Let fdset_shrink be able to remove an fd
in the middle.

> +
> +		pthread_mutex_unlock(&pfdset->fd_mutex);
>  	}
>  }
> diff --git a/lib/librte_vhost/fd_man.h b/lib/librte_vhost/fd_man.h
> index bd66ed1..03e7881 100644
> --- a/lib/librte_vhost/fd_man.h
> +++ b/lib/librte_vhost/fd_man.h
> @@ -35,6 +35,7 @@
>  #define _FD_MAN_H_
>  #include <stdint.h>
>  #include <pthread.h>
> +#include <poll.h>
>  
>  #define MAX_FDS 1024
>  
> @@ -49,9 +50,10 @@ struct fdentry {
>  };
>  
>  struct fdset {
> +	struct pollfd rwfds[MAX_FDS];
>  	struct fdentry fd[MAX_FDS];
>  	pthread_mutex_t fd_mutex;
> -	int num;	/* current fd number of this fdset */
> +	int num;	/* highest index occupied in fd array + 1 */

I don't see the comment change makes it more readable.

	--yliu