On 20/07/2015 04:27, Fam Zheng wrote:
> For aio-posix, how about keeping the optimization local which doesn't need
> atomic operation? (no idea for win32 :)
>
> diff --git a/aio-posix.c b/aio-posix.c
> index 5c8b266..7e98123 100644
> --- a/aio-posix.c
> +++ b/aio-posix.c
> @@ -236,6 +236,7 @@ bool aio_poll(AioContext *ctx, bool blocking)
> int i, ret;
> bool progress;
> int64_t timeout;
> + int aio_notifier_idx = -1;
>
> aio_context_acquire(ctx);
> progress = false;
> @@ -256,11 +257,18 @@ bool aio_poll(AioContext *ctx, bool blocking)
> assert(npfd == 0);
>
> /* fill pollfds */
> + i = 0;
> QLIST_FOREACH(node, &ctx->aio_handlers, node) {
> if (!node->deleted && node->pfd.events) {
> add_pollfd(node);
> + if (node->pfd.fd == event_notifier_get_fd(&ctx->notifier)) {
> + assert(aio_notifier_idx == -1);
> + aio_notifier_idx = i;
> + }
> + i++;
> }
> }
That's a good idea. Since aio_set_fd_handler uses QLIST_INSERT_HEAD,
perhaps we can be sure that aio_notifier_idx is always the last one
(i.e. i-1)? And the same can be done on Windows, I think.
> + if (pollfds[aio_notifier_idx].revents & (G_IO_IN | G_IO_HUP | G_IO_ERR))
> {
> + event_notifier_test_and_clear(&ctx->notifier);
> + }
Might as well zero pollfds[aio_notifier_idx].revents after clearing it.
The atomic operation is not too expensive, so it would really be more
about simplicity than about speed. Not that simplicity is a bad thing!
I'll send v2 of the first patch, you can look at doing the optimization.
Thanks!
Paolo
