On Fri, Sep 09, 2011 at 05:46:20PM -0700, Ethan Jackson wrote: > > +/* Optimized flow revalidation. > > + * > > + * It's a difficult problem, in general, to tell which facets need to have > > + * their actions recalculated whenever the OpenFlow flow table changes. ?We > > + * don't try to solve that general problem: for most kinds of OpenFlow flow > > + * table changes, we recalculate the actions for every facet. ?This is > > + * relatively expensive, but it's good enough if the OpenFlow flow table > > + * doesn't change very often. > > + * > > + * However, we can expect one particular kind of OpenFlow flow table > > change to > > + * happen frequently: changes caused by MAC learning. ?To avoid wasting a > > lot > > + * of CPU on revalidating every facet whenever MAC learning modifies the > > flow > > + * table, we add a special case that applies to flow tables in which every > > rule > > + * has the same form (that is, the same wildcards), except that the table > > is > > + * also allowed to have a single "catch-all" flow that matches all > > packets. ?We > > + * optimize this case by tagging all of the facets that resubmit into the > > table > > + * and invalidating the same tag whenever a flow changes in that table. > > + */ > > I think this comment needs to more explicitly point out that these special > tables cause revalidation on a per rule basis not on a per table basis. When > I first read it, I thought the optimization was to revalidate all flows which > hit the table whenever any rule in the table changed.
I applied this, does it help? Or you can suggest better wording. diff --git a/ofproto/ofproto-dpif.c b/ofproto/ofproto-dpif.c index b9a27ae..93bc0d2 100644 --- a/ofproto/ofproto-dpif.c +++ b/ofproto/ofproto-dpif.c @@ -4034,8 +4034,10 @@ done: * has the same form (that is, the same wildcards), except that the table is * also allowed to have a single "catch-all" flow that matches all packets. We * optimize this case by tagging all of the facets that resubmit into the table - * and invalidating the same tag whenever a flow changes in that table. - */ + * and invalidating the same tag whenever a flow changes in that table. The + * end result is that we revalidate just the facets that need it (and sometimes + * a few more, but not all of the facets or even all of the facets that + * resubmit to the table modified by MAC learning). */ /* Calculates the tag to use for 'flow' and wildcards 'wc' when it is inserted * into an OpenFlow table with the given 'basis'. */ _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
