On Thu, Oct 30, 2014 at 08:26:15AM -0700, Ben Pfaff wrote: > On Thu, Oct 30, 2014 at 12:06:30PM +0100, Thomas Graf wrote: > > On 10/29/14 at 11:46pm, Ben Pfaff wrote: > > > A "conjunctive match" allows higher-level matches in the flow table, such > > > as set membership matches, without causing a cross-product explosion for > > > multidimensional matches. Please refer to the documentation that this > > > commit adds to ovs-ofctl(8) for a better explanation, including an > > > example. > > > > High level remark before I dig into the code: > > > > conjunction(id, k/n) > > > > I like n being the number of dimensions. I wonder whether we should > > have k start at 1 instead of 0 though. It would read as 1/2 - "1st > > dimension out of 2", 2/2 - "2nd dimension out of 2". > > I'd be happy with that as the formatted syntax, but due to the use of > bitmaps for the dimensions it would either cause extra +1/-1 in > different places, or change the limit from 64 to 63 dimensions (which is > probably still about 60 more than actually useful). > > I'll think about it for the next version.
I decided to change the formatted representation but not the OpenFlow binary format; that is, the formatting and parsing code for the human-readable representation adds or subtracts one from the dimension numbers. This change will be in the next version I post. > > > - Fixing reg0 as the field to use for conjunctive match lookup doesn't > > > seem > > > too great. We could make it configurable per-flow, or we could add a > > > new > > > field specifically for this purpose. I am not sure that it should be > > > fixed to 32 bits, either. > > > > I guess we can't go wrong with a separate 64 bits field. > > We're starting to have a lot of fields. When struct flow exceeds 252 > (63 * 4) bytes, we'll have to change how struct miniflow works because > we can't make the 'map' member wider than 63 bits. Still, we do have > some room. Jarno also suggested using a dedicated field, so I went with that. At the moment it is 32 bits. That would not be difficult to change, but it would extend NXAST_CONJUNCTION from 16 to 24 bytes. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
