From: "Wu, Jingjing" <jingjing.wu@intel.com>
To: "Yigit, Ferruh" <ferruh.yigit@intel.com>,
Vladyslav Buslov <vladyslav.buslov@harmonicinc.com>,
"Zhang, Helin" <helin.zhang@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] net/i40e: add additional prefetch instructions for bulk rx
Date: Mon, 10 Oct 2016 13:25:57 +0000 [thread overview]
Message-ID: <9BB6961774997848B5B42BEC655768F80E277DFC@SHSMSX103.ccr.corp.intel.com> (raw)
In-Reply-To: <18156776-3658-a97d-3fbc-19c1a820a04d@intel.com>
> -----Original Message-----
> From: Yigit, Ferruh
> Sent: Wednesday, September 14, 2016 9:25 PM
> To: Vladyslav Buslov <vladyslav.buslov@harmonicinc.com>; Zhang, Helin
> <helin.zhang@intel.com>; Wu, Jingjing <jingjing.wu@intel.com>
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] net/i40e: add additional prefetch instructions for bulk rx
>
> On 7/14/2016 6:27 PM, Vladyslav Buslov wrote:
> > Added prefetch of first packet payload cacheline in i40e_rx_scan_hw_ring
> > Added prefetch of second mbuf cacheline in i40e_rx_alloc_bufs
> >
> > Signed-off-by: Vladyslav Buslov <vladyslav.buslov@harmonicinc.com>
> > ---
> > drivers/net/i40e/i40e_rxtx.c | 7 +++++--
> > 1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/i40e/i40e_rxtx.c b/drivers/net/i40e/i40e_rxtx.c
> > index d3cfb98..e493fb4 100644
> > --- a/drivers/net/i40e/i40e_rxtx.c
> > +++ b/drivers/net/i40e/i40e_rxtx.c
> > @@ -1003,6 +1003,7 @@ i40e_rx_scan_hw_ring(struct i40e_rx_queue *rxq)
> > /* Translate descriptor info to mbuf parameters */
> > for (j = 0; j < nb_dd; j++) {
> > mb = rxep[j].mbuf;
> > + rte_prefetch0(RTE_PTR_ADD(mb->buf_addr,
> RTE_PKTMBUF_HEADROOM));
Why did prefetch here? I think if application need to deal with packet, it is more suitable to put it in application.
> > qword1 = rte_le_to_cpu_64(\
> > rxdp[j].wb.qword1.status_error_len);
> > pkt_len = ((qword1 &
> I40E_RXD_QW1_LENGTH_PBUF_MASK) >>
> > @@ -1086,9 +1087,11 @@ i40e_rx_alloc_bufs(struct i40e_rx_queue *rxq)
> >
> > rxdp = &rxq->rx_ring[alloc_idx];
> > for (i = 0; i < rxq->rx_free_thresh; i++) {
> > - if (likely(i < (rxq->rx_free_thresh - 1)))
> > + if (likely(i < (rxq->rx_free_thresh - 1))) {
> > /* Prefetch next mbuf */
> > - rte_prefetch0(rxep[i + 1].mbuf);
> > + rte_prefetch0(&rxep[i + 1].mbuf->cacheline0);
> > + rte_prefetch0(&rxep[i + 1].mbuf->cacheline1);
> > + }
Agree with this change. And when I test it by testpmd with iofwd, no performance increase is observed but minor decrease.
Can you share will us when it will benefit the performance in your scenario ?
Thanks
Jingjing
next prev parent reply other threads:[~2016-10-10 13:26 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-14 17:27 [dpdk-dev] [PATCH] Add missing prefetches to i40e bulk rx path Vladyslav Buslov
2016-07-14 17:27 ` [dpdk-dev] [PATCH] net/i40e: add additional prefetch instructions for bulk rx Vladyslav Buslov
2016-09-14 13:24 ` Ferruh Yigit
2016-10-10 13:25 ` Wu, Jingjing [this message]
2016-10-10 17:05 ` Vladyslav Buslov
2016-10-11 8:51 ` Ananyev, Konstantin
2016-10-11 9:24 ` Vladyslav Buslov
2016-10-12 0:04 ` Ananyev, Konstantin
2016-10-13 10:18 ` Bruce Richardson
2016-10-13 10:30 ` Ananyev, Konstantin
2016-11-15 12:19 ` Ferruh Yigit
2016-11-15 13:27 ` Vladyslav Buslov
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