On Wed, 05 Apr 2017 11:37:39 +0200, Thomas Monjalon <thomas.monja...@6wind.com> wrote: > 2017-04-04 18:27, Olivier Matz: > > Based on discussions done in [1] and in this thread, this patchset > > reorganizes > > the mbuf. > > > > The main changes are: > > - reorder structure to increase vector performance on some non-ia > > platforms. > > - add a 64bits timestamp field in the 1st cache line. This timestamp > > is not normalized, i.e. no unit or time reference is enforced. A > > library may be added to do this job in the future. > > - m->next, m->nb_segs, and m->refcnt are always initialized for mbufs > > in the pool, avoiding the need of setting m->next (located in the > > 2nd cache line) in the Rx path for mono-segment packets. > > - change port and nb_segs to 16 bits > > - move seqn in the 2nd cache line > > Applied, thanks for the long work > > We need to add a patch to bump ABIVER and document the changes.
Thanks Thomas. I'm on it, I will send it ASAP. > > Things discussed but not done in the patchset: > > - move refcnt and nb_segs to the 2nd cache line: many drivers sets > > them in the Rx path, so it could introduce a performance regression, or > > it would require to change all the drivers, which is not an easy task. > > If it is worth to move these fields in 2nd cache line, > can we plan to rework drivers for not setting them in Rx? I think it's worth doing the driver modification, it may gain some cycles. Once it's done, it becomes easy to see the impact of moving the fields... except if it breaks a vector code ;) I think this move should only occur if we need more room in the first cache line. > > > Once this patchset is pushed, the Rx path of drivers could be optimized a > > bit, > > by removing writes to m->next, m->nb_segs and m->refcnt. The patch 4/8 > > gives an > > idea of what could be done. > > Yes drivers patches are welcome :) > Please target RC2 for these changes. >
