On Fri, 18 Sep 2015 11:33:36 +0100 Alejandro Lucero <alejandro.lucero at netronome.com> wrote:
> I have seen the API definition says nothing about accuracy but some PMD > implementations sacrifice accuracy for the sake of performance. If I'm not > understanding the code wrongly i40e and ixgbe check DD bit just for the > first descriptor in a group of 4, and they take all of them as used if the > first descriptor is used. > > By other hand, they do a "heavy" calculation when the descriptor ring wraps > which does not make sense (to me) if same performance goal is used. > > There are PMDs not supporting this option and I can not see any app or > example using it so I do not know how important is this function, its > accuracy and its performance impact. Can someone comment on this? > > Thanks I have version of this for virtio/vmxnet3 It is useful when using the interrupt control mode.