On Wed, 2013-06-05 at 16:41 +0300, Eliezer Tamir wrote: > On 05/06/2013 16:30, Eric Dumazet wrote: > > On Wed, 2013-06-05 at 13:34 +0300, Eliezer Tamir wrote: > >> A very naive select/poll busy-poll support. > >> Add busy-polling to sock_poll(). > >> When poll/select have nothing to report, call the low-level > >> sock_poll() again until we are out of time or we find something. > >> Right now we poll every socket once, this is suboptimal > >> but improves latency when the number of sockets polled is not large. > >> > >> Signed-off-by: Alexander Duyck <alexander.h.du...@intel.com> > >> Signed-off-by: Jesse Brandeburg <jesse.brandeb...@intel.com> > >> Tested-by: Willem de Bruijn <will...@google.com> > >> Signed-off-by: Eliezer Tamir <eliezer.ta...@linux.intel.com> > >> --- > > > > I am a bit uneasy with this one, because an applicatio polling() on one > > thousand file descriptors using select()/poll(), will call sk_poll_ll() > > one thousand times. > > But we call sk_poll_ll() with nonblock set, so it will only test once > for each socket and not loop. > > I think this is not as bad as it sounds. > We still honor the time limit on how long to poll. > > When we busy-wait on a single socket we call sk_poll_ll() repeatedly > until we timeout or we have something to report. > > Here on the other hand, we sk_poll_ll() once for each file, so we loop > on the files. We moved the loop from inside sk_poll_ll to select/poll. > > I also plan on improving this this in the next stage. > > The plan is to give control on whether sk_poll_ll is called to > select/poll/epoll, so the caller has even more control.
This looks quite easy, by adding in include/uapi/asm-generic/poll.h #define POLL_LL 0x8000 And do the sk_poll_ll() call only if flag is set. I do not think we have to support select(), as its legacy interface, and people wanting ll should really use epoll() or poll(). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
