lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Fri, 24 Aug 2007 21:04:56 +0200 From: Bodo Eggert <7eggert@....de> To: Linas Vepstas <linas@...tin.ibm.com>, Jan-Bernd Themann <ossthema@...ibm.com>, netdev <netdev@...r.kernel.org>, Thomas Klein <tklein@...ibm.com>, Jan-Bernd Themann <themann@...ibm.com>, linux-kernel <linux-kernel@...r.kernel.org>, linux-ppc <linuxppc-dev@...abs.org>, Christoph Raisch <raisch@...ibm.com>, Marcus Eder <meder@...ibm.com>, Stefan Roscher <stefan.roscher@...ibm.com> Subject: Re: RFC: issues concerning the next NAPI interface Linas Vepstas <linas@...tin.ibm.com> wrote: > On Fri, Aug 24, 2007 at 03:59:16PM +0200, Jan-Bernd Themann wrote: >> 3) On modern systems the incoming packets are processed very fast. Especially >> on SMP systems when we use multiple queues we process only a few packets >> per napi poll cycle. So NAPI does not work very well here and the interrupt >> rate is still high. > > I saw this too, on a system that is "modern" but not terribly fast, and > only slightly (2-way) smp. (the spidernet) > > I experimented wih various solutions, none were terribly exciting. The > thing that killed all of them was a crazy test case that someone sprung on > me: They had written a worst-case network ping-pong app: send one > packet, wait for reply, send one packet, etc. > > If I waited (indefinitely) for a second packet to show up, the test case > completely stalled (since no second packet would ever arrive). And if I > introduced a timer to wait for a second packet, then I just increased > the latency in the response to the first packet, and this was noticed, > and folks complained. Possible solution / possible brainfart: Introduce a timer, but don't start to use it to combine packets unless you receive n packets within the timeframe. If you receive less than m packets within one timeframe, stop using the timer. The system should now have a decent response time when the network is idle, and when the network is busy, nobody will complain about the latency.-) -- Funny quotes: 22. When everything's going your way, you're in the wrong lane and and going the wrong way. Friß, Spammer: rsRxhvmk@....7eggert.dyndns.org m@....7eggert.dyndns.org - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists