Date: Tue, 24 Apr 2012 17:40:13 +0000 From: "Li, Qing" <qing.li@bluecoat.com> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: "current@freebsd.org" <current@freebsd.org>, "net@freebsd.org" <net@freebsd.org> Subject: RE: Some performance measurements on the FreeBSD network stack Message-ID: <B143A8975061C446AD5E29742C531723C7CA49@pwsvl-excmbx-05.internal.cacheflow.com> In-Reply-To: <20120424163423.GA59530@onelab2.iet.unipi.it> References: <20120419133018.GA91364@onelab2.iet.unipi.it> <4F907011.9080602@freebsd.org> <20120419204622.GA94904@onelab2.iet.unipi.it> <B143A8975061C446AD5E29742C531723C7C16A@pwsvl-excmbx-05.internal.cacheflow.com> <20120424163423.GA59530@onelab2.iet.unipi.it>
next in thread | previous in thread | raw e-mail | index | archive | help
Yup, all good points. In fact we have considered all of these while doing the work. In case you haven't seen it already, we did write about these=20 issues in our paper and how we tried to address those, flow-table was one of the solutions. http://dl.acm.org/citation.cfm?id=3D1592641 --Qing > > > > Well, the routing table no longer maintains any lle info, so there > > isn't much to copy out the rtentry at the completion of route > > lookup. > > > > If I understood you correctly, you do believe there is a lot of value > > in Flowtable caching concept, but you are not suggesting we reverting > > back to having the routing table maintain L2 entries, are you ? >=20 > I see a lot of value in caching in general. >=20 > Especially for a bound socket it seems pointless to lookup the > route, iface and mac address(es) on every single packet instead of > caching them. And, routes and MAC addresses are volatile anyways > so making sure that we do the lookup 1us closer to the actual use > gives no additional guarantee. >=20 > The frequency with which these info (routes and MAC addresses) > change clearly influences the mechanism to validate the cache. > I suppose we have the following options: >=20 > - direct notification: a failure in a direct chain of calls > can be used to invalidate the info cached in the socket. > Similarly, some incoming traffic (e.g. TCP RST, FIN, > ICMP messages) that reach a socket can invalidate the cached values > - assume a minimum lifetime for the info (i think this is what > happens in the flowtable) and flush it unconditionally > every such interval (say 10ms). > - if some info changes infrequently (e.g. MAC addresses) one could > put a version number in the cached value and use it to validate > the cache. >=20 > cheers > luigi
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?B143A8975061C446AD5E29742C531723C7CA49>