Gleb Smirnoff wrote this message on Sat, Mar 28, 2015 at 11:34 +0300: > On Fri, Mar 27, 2015 at 01:26:59PM +0000, Fabien Thomas wrote: > F> Author: fabient > F> Date: Fri Mar 27 13:26:59 2015 > F> New Revision: 280759 > F> URL: https://svnweb.freebsd.org/changeset/base/280759 > F> > F> Log: > F> On multi CPU systems, we may emit successive packets with the same id. > F> Fix the race by using an atomic operation. > F> > F> Differential Revision: https://reviews.freebsd.org/D2141 > F> Obtained from: emeric.pou...@stormshield.eu > F> MFC after: 1 week > F> Sponsored by: Stormshield > > The D2141 says that benchmarking were done in presence of IPSEC, which > of course is the bottleneck and performance of this instruction can't > be benchmarked in its presence. Anyway, I believe that results of > right benchmark would still show little difference between atomic and > non-atomic increment of a shared value. > > I think we can use per-cpu ID counters, each CPU incrementing its > own. If we start with random values, then probability of two packets with > the same ID emitting at the allowed timeframe will be acceptably small.
Please do not use per-cpu id counters.. That will just push the duplicate ids to being more rare, but just as much of a problem... Please read: https://tools.ietf.org/html/rfc6864 And then implement one hased upon source/dest/protocol... Thanks. -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not." _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
