> -----Original Message----- > From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Ananyev, > Konstantin > Sent: Friday, March 31, 2017 3:01 AM > > After applying the patch below got nearly original numbers (though not > quite) on my box. > dpdk.org mainline: 50.8 > with Olivier patch: 47.8 > with patch below: 50.4 > What I tried to do in it - avoid unnecessary updates of mbuf inside > rte_pktmbuf_prefree_seg(). > For one segment per packet it seems to help. > Though so far I didn't try it on i40e and didn't do any testing for > multi-seg scenario. > Konstantin > > $ cat patch.mod4 > diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h > index d7af852..558233f 100644 > --- a/lib/librte_mbuf/rte_mbuf.h > +++ b/lib/librte_mbuf/rte_mbuf.h > @@ -1283,12 +1283,28 @@ rte_pktmbuf_prefree_seg(struct rte_mbuf *m) { > __rte_mbuf_sanity_check(m, 0); > > - if (likely(rte_mbuf_refcnt_update(m, -1) == 0)) { > + if (likely(rte_mbuf_refcnt_read(m) == 1)) { > + > + if (m->next != NULL) { > + m->next = NULL; > + m->nb_segs = 1; > + } > + > + if (RTE_MBUF_INDIRECT(m)) > + rte_pktmbuf_detach(m); > + > + return m; > + > + } else if (rte_atomic16_add_return(&m->refcnt_atomic, -1) == 0) > + { > + > if (RTE_MBUF_INDIRECT(m)) > rte_pktmbuf_detach(m); > > - m->next = NULL; > - m->nb_segs = 1; > + if (m->next != NULL) { > + m->next = NULL; > + m->nb_segs = 1; > + } > + > rte_mbuf_refcnt_set(m, 1); > > return m;
Maybe the access to the second cache line (for single-segment packets) can be avoided altogether in rte_pktmbuf_prefree_seg() by adding a multi-segment indication flag to the first cache line, and using this flag instead of the test for m->next != NULL. Med venlig hilsen / kind regards - Morten Brørup
