[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v7 2/2] public/io/netif.h: document control ring and toeplitz hashing
On Mon, 2016-01-18 at 09:35 -0700, Jan Beulich wrote: > > > > On 18.01.16 at 17:07, <ian.campbell@xxxxxxxxxx> wrote: > > On Tue, 2016-01-12 at 09:58 +0000, Paul Durrant wrote: > > > + * NETIF_CTRL_TYPE_SET_TOEPLITZ_MAPPING > > > + * ------------------------------------ > > > + * > > > + * This is sent by the frontend to set the content of the table > > > mapping > > > + * toeplitz hash value to queue number. The backend should calculate > > > the > > > + * hash from the packet header, use it as an index into the table > > > (modulo > > > + * the size of the table) and then steer the packet to the queue > > > number > > > + * found at that index. > > > + * > > > + * Request: > > > + * > > > + *ÂÂtypeÂÂÂÂ= NETIF_CTRL_TYPE_SET_TOEPLITZ_MAPPING > > > + *ÂÂdata[0] = grant reference of page containing the mapping (sub- > > > )table > > > + *ÂÂÂÂÂÂÂÂÂÂÂÂ(assumed to start at beginning of grant) > > > + *ÂÂdata[1] = size of (sub-)table in entries > > > + *ÂÂdata[2] = offset, in entries, of sub-table within overall table > > > > Adding data[2] seems reasonable to me, but if you wanted to avoid > > adding it > > then saying data[1][8:0] == size and data[1][31:9] == offset would > > allow a > > size of 512 (biggest possible in a single gref) and 8.3M for the > > offset. > > I may be lacking some context here, so please ignore if it reads > like nonsense, but is the 9-bit width bound to a page size of 4k, > or an inherent property of the Toeplitz algorithm? The table entries are 8 bytes, so in that respect yes I suppose it is related to the page size. Paul thought it best not to do this any. > In the former > case I think we should try to avoid putting further limitations to > 4k pages into any interface. (And as an aside, 512 is also not > representable in 9 bits, but this can clearly be addressed quite > easily.) Indeed, looks like I miscounted. Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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