From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.tuxdriver.com (charlotte.tuxdriver.com [70.61.120.58]) by dpdk.org (Postfix) with ESMTP id 92EB2312 for ; Tue, 30 Sep 2014 16:26:19 +0200 (CEST) Received: from hmsreliant.think-freely.org ([2001:470:8:a08:7aac:c0ff:fec2:933b] helo=localhost) by smtp.tuxdriver.com with esmtpsa (TLSv1:AES128-SHA:128) (Exim 4.63) (envelope-from ) id 1XYyTr-00063P-Lo; Tue, 30 Sep 2014 10:32:59 -0400 Date: Tue, 30 Sep 2014 10:32:42 -0400 From: Neil Horman To: Hiroshi Shimamoto Message-ID: <20140930143242.GI2193@hmsreliant.think-freely.org> References: <7F861DC0615E0C47A872E6F3C5FCDDBD02AE26C5@BPXM14GP.gisp.nec.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7F861DC0615E0C47A872E6F3C5FCDDBD02AE26C5@BPXM14GP.gisp.nec.co.jp> User-Agent: Mutt/1.5.23 (2014-03-12) X-Spam-Score: -2.9 (--) X-Spam-Status: No Cc: "dev@dpdk.org" , Hayato Momma Subject: Re: [dpdk-dev] [memnic PATCH v2 6/7] pmd: add branch hint in recv/xmit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 30 Sep 2014 14:26:19 -0000 On Tue, Sep 30, 2014 at 11:14:40AM +0000, Hiroshi Shimamoto wrote: > From: Hiroshi Shimamoto > > 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 > Reviewed-by: Hayato Momma > --- > 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))) { Why are you using ACCESS_ONCE here? Or for that matter, anywhere else in this PMD? The whole idea of the ACCESS_ONCE macro is to assign a value to a variable once and prevent it from getting reloaded from memory at a later time, this is exactly contrary to that, both in the sense that you're explicitly reloading the same variable multiple times, and that you're using it as part of a comparison operation, rather than an asignment operation Neil