Wow. Great catch.
The description says it stopped calling poll_fd_woke() (which it's ultimately
doing), but the call in this function is nl_sock_woke().
It might be nice to explain why this improvement works over a theoretical
optimization.
--Justin
On Nov 22, 2011, at 3:12 PM, Ben Pfaff wrote:
> This optimization on its own provides about 37% benefit against a
> load of a single netperf CRR test, but at the same time it penalizes
> ovs-benchmark by about 11%. We can get back the CRR performance
> loss, and more, other ways, so the first step is to revert this
> patch.
> ---
> lib/dpif-linux.c | 47 +++++++++++++++++++++++------------------------
> 1 files changed, 23 insertions(+), 24 deletions(-)
>
> diff --git a/lib/dpif-linux.c b/lib/dpif-linux.c
> index 88193c3..4b4ac55 100644
> --- a/lib/dpif-linux.c
> +++ b/lib/dpif-linux.c
> @@ -1097,39 +1097,38 @@ dpif_linux_recv(struct dpif *dpif_, struct
> dpif_upcall *upcall)
>
> for (i = 0; i < N_UPCALL_SOCKS; i++) {
> struct nl_sock *upcall_sock;
> + int dp_ifindex;
> +
> dpif->last_read_upcall = (dpif->last_read_upcall + 1) &
> (N_UPCALL_SOCKS - 1);
> upcall_sock = dpif->upcall_socks[dpif->last_read_upcall];
>
> - if (nl_sock_woke(upcall_sock)) {
> - int dp_ifindex;
>
> - for (;;) {
> - struct ofpbuf *buf;
> - int error;
> + for (;;) {
> + struct ofpbuf *buf;
> + int error;
>
> - if (++read_tries > 50) {
> - return EAGAIN;
> - }
> + if (++read_tries > 50) {
> + return EAGAIN;
> + }
>
> - error = nl_sock_recv(upcall_sock, &buf, false);
> - if (error == EAGAIN) {
> - break;
> - } else if (error) {
> - return error;
> - }
> + error = nl_sock_recv(upcall_sock, &buf, false);
> + if (error == EAGAIN) {
> + break;
> + } else if (error) {
> + return error;
> + }
>
> - error = parse_odp_packet(buf, upcall, &dp_ifindex);
> - if (!error
> - && dp_ifindex == dpif->dp_ifindex
> - && dpif->listen_mask & (1u << upcall->type)) {
> - return 0;
> - }
> + error = parse_odp_packet(buf, upcall, &dp_ifindex);
> + if (!error
> + && dp_ifindex == dpif->dp_ifindex
> + && dpif->listen_mask & (1u << upcall->type)) {
> + return 0;
> + }
>
> - ofpbuf_delete(buf);
> - if (error) {
> - return error;
> - }
> + ofpbuf_delete(buf);
> + if (error) {
> + return error;
> }
> }
> }
> --
> 1.7.4.4
>
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> dev@openvswitch.org
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