The x4 variant was introduced chronologically after the sample plugin and nobody went back to update it. However, generally speaking the four-wide-stride is only beneficial in some cases, the reasoning for which is a bit arcane based on the likelihood of being able to keep the CPU cache primed and similar. The best I can tell is that there's a bit of judgement based on the empirical experience of a handful of the wizened. By extension the gains from a x8 version is likely marginal.
Chris > -----Original Message----- > From: vpp-dev-boun...@lists.fd.io [mailto:vpp-dev-boun...@lists.fd.io] On > Behalf Of Justin Iurman > Sent: Monday, November 13, 2017 5:51 AM > To: vpp-dev <vpp-dev@lists.fd.io> > Subject: [vpp-dev] vlib_validate_buffer_enqueue > > Hey guys, > > In buffer_node.h, there are the following macros: > - vlib_validate_buffer_enqueue_x1 > - vlib_validate_buffer_enqueue_x2 > - vlib_validate_buffer_enqueue_x4 > > In a node, I was just wondering what was the use idea behind that ? Is it for > a > reason of speed ? I mean, you're obviously faster if you process 4 packets > horizontally than one after the other. Why then, in the sample plugin, is the > "x4" version not used ? A "perfect" plugin would use each of them to cover > each case, right ? Also, why not having a "x8" (or more) version ? I guess > it's > either for a performance issue or to stop at a specific ceiling. > > Thanks ! > > Justin > _______________________________________________ > vpp-dev mailing list > vpp-dev@lists.fd.io > https://lists.fd.io/mailman/listinfo/vpp-dev _______________________________________________ vpp-dev mailing list vpp-dev@lists.fd.io https://lists.fd.io/mailman/listinfo/vpp-dev
