From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH v9 net-next 5/7] net: simple poll/select low latency socket poll Date: Wed, 05 Jun 2013 06:56:47 -0700 Message-ID: <1370440607.24311.251.camel@edumazet-glaptop> References: <20130605103400.11172.49099.stgit@ladj378.jer.intel.com> <20130605103452.11172.31453.stgit@ladj378.jer.intel.com> <1370439054.24311.248.camel@edumazet-glaptop> <51AF401C.2030506@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Willem de Bruijn , Don, Or Gerlitz , e1000-devel@lists.sourceforge.net, netdev@vger.kernel.org, HPA , Amir Vadai , Jesse Brandeburg , Eliezer Tamir , linux-kernel@vger.kernel.org, Andi Kleen , Ben Hutchings , Eilon Greenstien , David Miller To: Eliezer Tamir Return-path: In-Reply-To: <51AF401C.2030506@linux.intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: e1000-devel-bounces@lists.sourceforge.net List-Id: netdev.vger.kernel.org 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 > >> Signed-off-by: Jesse Brandeburg > >> Tested-by: Willem de Bruijn > >> Signed-off-by: Eliezer Tamir > >> --- > > > > 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(). ------------------------------------------------------------------------------ How ServiceNow helps IT people transform IT departments: 1. A cloud service to automate IT design, transition and operations 2. Dashboards that offer high-level views of enterprise services 3. A single system of record for all IT processes http://p.sf.net/sfu/servicenow-d2d-j _______________________________________________ E1000-devel mailing list E1000-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/e1000-devel To learn more about Intel® Ethernet, visit http://communities.intel.com/community/wired