The patch is ok. For the commit message, is it better "to reduce branch mispredication"?
> -----Original Message----- > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Hiroshi Shimamoto > Sent: Tuesday, September 30, 2014 7:15 PM > To: dev at dpdk.org > Cc: Hayato Momma > Subject: [dpdk-dev] [memnic PATCH v2 6/7] pmd: add branch hint in recv/xmit > > From: Hiroshi Shimamoto <h-shimamoto at ct.jp.nec.com> > > To reduce instruction cache miss, add branch condition hints into > recv/xmit functions. This improves a bit performance. > > We can see performance improvements with memnic-tester. > Using Xeon E5-2697 v2 @ 2.70GHz, 4 vCPU. > size | before | after > 64 | 5.54Mpps | 5.55Mpps > 128 | 5.46Mpps | 5.44Mpps > 256 | 5.21Mpps | 5.22Mpps > 512 | 4.50Mpps | 4.52Mpps > 1024 | 3.71Mpps | 3.73Mpps > 1280 | 3.21Mpps | 3.22Mpps > 1518 | 2.92Mpps | 2.93Mpps > > Signed-off-by: Hiroshi Shimamoto <h-shimamoto at ct.jp.nec.com> > Reviewed-by: Hayato Momma <h-momma at ce.jp.nec.com> > --- > pmd/pmd_memnic.c | 18 +++++++++--------- > 1 file changed, 9 insertions(+), 9 deletions(-) > > diff --git a/pmd/pmd_memnic.c b/pmd/pmd_memnic.c > index 7fc3093..875d3ea 100644 > --- a/pmd/pmd_memnic.c > +++ b/pmd/pmd_memnic.c > @@ -289,26 +289,26 @@ static uint16_t memnic_recv_pkts(void *rx_queue, > int idx, next; > struct rte_eth_stats *st = &adapter->stats[rte_lcore_id()]; > > - if (!adapter->nic->hdr.valid) > + if (unlikely(!adapter->nic->hdr.valid)) > return 0; > > pkts = bytes = errs = 0; > idx = adapter->up_idx; > for (nr = 0; nr < nb_pkts; nr++) { > p = &data->packets[idx]; > - if (p->status != MEMNIC_PKT_ST_FILLED) > + if (unlikely(p->status != MEMNIC_PKT_ST_FILLED)) > break; > /* prefetch the next area */ > next = idx; > - if (++next >= MEMNIC_NR_PACKET) > + if (unlikely(++next >= MEMNIC_NR_PACKET)) > next = 0; > rte_prefetch0(&data->packets[next]); > - if (p->len > framesz) { > + if (unlikely(p->len > framesz)) { > errs++; > goto drop; > } > mb = rte_pktmbuf_alloc(adapter->mp); > - if (!mb) > + if (unlikely(!mb)) > break; > > rte_memcpy(rte_pktmbuf_mtod(mb, void *), p->data, p->len); > @@ -350,7 +350,7 @@ static uint16_t memnic_xmit_pkts(void *tx_queue, > uint64_t pkts, bytes, errs; > uint32_t framesz = adapter->framesz; > > - if (!adapter->nic->hdr.valid) > + if (unlikely(!adapter->nic->hdr.valid)) > return 0; > > pkts = bytes = errs = 0; > @@ -360,7 +360,7 @@ static uint16_t memnic_xmit_pkts(void *tx_queue, > struct rte_mbuf *sg; > void *ptr; > > - if (pkt_len > framesz) { > + if (unlikely(pkt_len > framesz)) { > errs++; > break; > } > @@ -379,7 +379,7 @@ retry: > goto retry; > } > > - if (idx != ACCESS_ONCE(adapter->down_idx)) { > + if (unlikely(idx != ACCESS_ONCE(adapter->down_idx))) { > /* > * host freed this and got false positive, > * need to recover the status and retry. > @@ -388,7 +388,7 @@ retry: > goto retry; > } > > - if (++idx >= MEMNIC_NR_PACKET) > + if (unlikely(++idx >= MEMNIC_NR_PACKET)) > idx = 0; > adapter->down_idx = idx; > > -- > 1.8.3.1
