I didn't experiment. The dpif-linux fds have the advantage of being
static and unchanging from one iteration to the next. It might be worth
a try later.
On Thu, Nov 24, 2011 at 10:28:45AM -0800, Justin Pettit wrote:
> Looks good. Do you think there's benefit in using epoll in the main
> poll library?
>
> --Justin
>
>
> On Nov 22, 2011, at 3:12 PM, Ben Pfaff wrote:
>
> > epoll appears to be much more efficient than poll() at least for
> > static file descriptor sets. I can't otherwise explain why this
> > patch increases netperf CRR performance by 20% above the previous
> > commit, which is also about a 19% overall improvement versus
> > the baseline from before the poll_fd_woke() optimization was
> > removed.
> > ---
> > lib/dpif-linux.c | 54
> > +++++++++++++++++++++++++++++++-----------------------
> > 1 files changed, 31 insertions(+), 23 deletions(-)
> >
> > diff --git a/lib/dpif-linux.c b/lib/dpif-linux.c
> > index 75e4301..d71fa2a 100644
> > --- a/lib/dpif-linux.c
> > +++ b/lib/dpif-linux.c
> > @@ -31,6 +31,7 @@
> > #include <poll.h>
> > #include <stdlib.h>
> > #include <strings.h>
> > +#include <sys/epoll.h>
> > #include <sys/stat.h>
> > #include <unistd.h>
> >
> > @@ -140,6 +141,7 @@ struct dpif_linux {
> > struct nl_sock *upcall_socks[N_UPCALL_SOCKS];
> > uint32_t nonempty_socks;
> > unsigned int listen_mask;
> > + int epoll_fd;
> >
> > /* Change notification. */
> > struct sset changed_ports; /* Ports that have changed. */
> > @@ -274,6 +276,7 @@ open_dpif(const struct dpif_linux_dp *dp, struct dpif
> > **dpifp)
> > dpif = xzalloc(sizeof *dpif);
> > dpif->port_notifier = nln_notifier_create(nln, dpif_linux_port_changed,
> > dpif);
> > + dpif->epoll_fd = -1;
> >
> > dpif_init(&dpif->dpif, &dpif_linux_class, dp->name,
> > dp->dp_ifindex, dp->dp_ifindex);
> > @@ -294,6 +297,10 @@ destroy_upcall_socks(struct dpif_linux *dpif)
> > {
> > int i;
> >
> > + if (dpif->epoll_fd >= 0) {
> > + close(dpif->epoll_fd);
> > + dpif->epoll_fd = -1;
> > + }
> > for (i = 0; i < N_UPCALL_SOCKS; i++) {
> > nl_sock_destroy(dpif->upcall_socks[i]);
> > dpif->upcall_socks[i] = NULL;
> > @@ -1005,12 +1012,28 @@ dpif_linux_recv_set_mask(struct dpif *dpif_, int
> > listen_mask)
> > int i;
> > int error;
> >
> > + dpif->epoll_fd = epoll_create(N_UPCALL_SOCKS);
> > + if (dpif->epoll_fd < 0) {
> > + return errno;
> > + }
> > +
> > for (i = 0; i < N_UPCALL_SOCKS; i++) {
> > + struct epoll_event event;
> > +
> > error = nl_sock_create(NETLINK_GENERIC, &dpif->upcall_socks[i]);
> > if (error) {
> > destroy_upcall_socks(dpif);
> > return error;
> > }
> > +
> > + event.events = EPOLLIN;
> > + event.data.u32 = i;
> > + if (epoll_ctl(dpif->epoll_fd, EPOLL_CTL_ADD,
> > + nl_sock_fd(dpif->upcall_socks[i]), &event) < 0) {
> > + error = errno;
> > + destroy_upcall_socks(dpif);
> > + return error;
> > + }
> > }
> >
> > dpif->nonempty_socks = 0;
> > @@ -1100,36 +1123,24 @@ dpif_linux_recv(struct dpif *dpif_, struct
> > dpif_upcall *upcall)
> > }
> >
> > if (!dpif->nonempty_socks) {
> > - struct pollfd pfds[N_UPCALL_SOCKS];
> > + struct epoll_event events[N_UPCALL_SOCKS];
> > int retval;
> > int i;
> >
> > - for (i = 0; i < N_UPCALL_SOCKS; i++) {
> > - pfds[i].fd = nl_sock_fd(dpif->upcall_socks[i]);
> > - pfds[i].events = POLLIN;
> > - pfds[i].revents = 0;
> > - }
> > -
> > do {
> > - retval = poll(pfds, N_UPCALL_SOCKS, 0);
> > + retval = epoll_wait(dpif->epoll_fd, events, N_UPCALL_SOCKS, 0);
> > } while (retval < 0 && errno == EINTR);
> > if (retval < 0) {
> > static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 1);
> > - VLOG_WARN_RL(&rl, "poll failed (%s)", strerror(errno));
> > - } else if (!retval) {
> > - return EAGAIN;
> > + VLOG_WARN_RL(&rl, "epoll_wait failed (%s)", strerror(errno));
> > }
> >
> > - for (i = 0; i < N_UPCALL_SOCKS; i++) {
> > - if (pfds[i].revents) {
> > - dpif->nonempty_socks |= 1u << i;
> > - }
> > + for (i = 0; i < retval; i++) {
> > + dpif->nonempty_socks |= 1u << events[i].data.u32;
> > }
> > -
> > - assert(dpif->nonempty_socks);
> > }
> >
> > - do {
> > + while (dpif->nonempty_socks) {
> > int indx = ffs(dpif->nonempty_socks) - 1;
> > struct nl_sock *upcall_sock = dpif->upcall_socks[indx];
> >
> > @@ -1163,7 +1174,7 @@ dpif_linux_recv(struct dpif *dpif_, struct
> > dpif_upcall *upcall)
> > return error;
> > }
> > }
> > - } while (dpif->nonempty_socks);
> > + }
> >
> > return EAGAIN;
> > }
> > @@ -1172,15 +1183,12 @@ static void
> > dpif_linux_recv_wait(struct dpif *dpif_)
> > {
> > struct dpif_linux *dpif = dpif_linux_cast(dpif_);
> > - int i;
> >
> > if (!dpif->listen_mask) {
> > return;
> > }
> >
> > - for (i = 0; i < N_UPCALL_SOCKS; i++) {
> > - nl_sock_wait(dpif->upcall_socks[i], POLLIN);
> > - }
> > + poll_fd_wait(dpif->epoll_fd, POLLIN);
> > }
> >
> > static void
> > --
> > 1.7.4.4
> >
> > _______________________________________________
> > dev mailing list
> > dev@openvswitch.org
> > http://openvswitch.org/mailman/listinfo/dev
>
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