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From: Neil Horman <nhorman@tuxdriver.com>
To: Bruce Richardson <bruce.richardson@intel.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH 2/5] ixgbe: add prefetch to improve slow-path tx perf
Date: Wed, 17 Sep 2014 11:21:03 -0400
Message-ID: <20140917152103.GE4213@localhost.localdomain> (raw)
In-Reply-To: <1410948102-12740-3-git-send-email-bruce.richardson@intel.com>

On Wed, Sep 17, 2014 at 11:01:39AM +0100, Bruce Richardson wrote:
> Make a small improvement to slow path TX performance by adding in a
> prefetch for the second mbuf cache line.
> Also move assignment of l2/l3 length values only when needed.
> 
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> ---
>  lib/librte_pmd_ixgbe/ixgbe_rxtx.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx.c b/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
> index 6f702b3..c0bb49f 100644
> --- a/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
> +++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
> @@ -565,25 +565,26 @@ ixgbe_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
>  		ixgbe_xmit_cleanup(txq);
>  	}
>  
> +	rte_prefetch0(&txe->mbuf->pool);
> +

Can you explain what all of these prefetches are doing?  It looks to me like
they're just fetching the first caheline of the mempool structure, which it
appears amounts to the pools name.  I don't see that having any use here.

>  	/* TX loop */
>  	for (nb_tx = 0; nb_tx < nb_pkts; nb_tx++) {
>  		new_ctx = 0;
>  		tx_pkt = *tx_pkts++;
>  		pkt_len = tx_pkt->pkt_len;
>  
> -		RTE_MBUF_PREFETCH_TO_FREE(txe->mbuf);
> -
>  		/*
>  		 * Determine how many (if any) context descriptors
>  		 * are needed for offload functionality.
>  		 */
>  		ol_flags = tx_pkt->ol_flags;
> -		vlan_macip_lens.f.vlan_tci = tx_pkt->vlan_tci;
> -		vlan_macip_lens.f.l2_l3_len = tx_pkt->l2_l3_len;
>  
>  		/* If hardware offload required */
>  		tx_ol_req = ol_flags & PKT_TX_OFFLOAD_MASK;
>  		if (tx_ol_req) {
> +			vlan_macip_lens.f.vlan_tci = tx_pkt->vlan_tci;
> +			vlan_macip_lens.f.l2_l3_len = tx_pkt->l2_l3_len;
> +
>  			/* If new context need be built or reuse the exist ctx. */
>  			ctx = what_advctx_update(txq, tx_ol_req,
>  				vlan_macip_lens.data);
> @@ -720,7 +721,7 @@ ixgbe_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
>  				    &txr[tx_id];
>  
>  				txn = &sw_ring[txe->next_id];
> -				RTE_MBUF_PREFETCH_TO_FREE(txn->mbuf);
> +				rte_prefetch0(&txn->mbuf->pool);
>  
>  				if (txe->mbuf != NULL) {
>  					rte_pktmbuf_free_seg(txe->mbuf);
> @@ -749,6 +750,7 @@ ixgbe_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
>  		do {
>  			txd = &txr[tx_id];
>  			txn = &sw_ring[txe->next_id];
> +			rte_prefetch0(&txn->mbuf->pool);
>  
>  			if (txe->mbuf != NULL)
>  				rte_pktmbuf_free_seg(txe->mbuf);
> -- 
> 1.9.3
> 
> 

  reply	other threads:[~2014-09-17 15:15 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-17 10:01 [dpdk-dev] [PATCH 0/5] Mbuf Structure Rework, part 3 Bruce Richardson
2014-09-17 10:01 ` [dpdk-dev] [PATCH 1/5] mbuf: ensure next pointer is set to null on free Bruce Richardson
2014-09-17 10:01 ` [dpdk-dev] [PATCH 2/5] ixgbe: add prefetch to improve slow-path tx perf Bruce Richardson
2014-09-17 15:21   ` Neil Horman [this message]
2014-09-17 15:35     ` Richardson, Bruce
2014-09-17 17:59       ` Neil Horman
2014-09-18 13:36         ` Bruce Richardson
2014-09-18 15:29           ` Neil Horman
2014-09-18 15:42             ` Bruce Richardson
2014-09-18 17:56               ` Neil Horman
2014-09-17 10:01 ` [dpdk-dev] [PATCH 3/5] testpmd: Change rxfreet default to 32 Bruce Richardson
2014-09-17 15:29   ` Neil Horman
2014-09-18 15:53     ` Richardson, Bruce
2014-09-18 17:13       ` Thomas Monjalon
2014-09-18 18:08         ` Neil Horman
2014-09-19  9:18           ` Richardson, Bruce
2014-09-19 10:24             ` Neil Horman
2014-09-19 10:28               ` Richardson, Bruce
2014-09-19 15:18                 ` Neil Horman
2014-09-18 18:03       ` Neil Horman
2014-09-17 10:01 ` [dpdk-dev] [PATCH 4/5] mbuf: add userdata pointer field Bruce Richardson
2014-09-17 15:35   ` Neil Horman
2014-09-17 16:02     ` Richardson, Bruce
2014-09-17 18:29       ` Neil Horman
2014-09-17 10:01 ` [dpdk-dev] [PATCH 5/5] mbuf: Add in second vlan tag field to mbuf Bruce Richardson
2014-09-17 20:46   ` Stephen Hemminger
2014-09-23 11:08 ` [dpdk-dev] [PATCH v2 0/5] Mbuf Structure Rework, part 3 Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 1/5] mbuf: ensure next pointer is set to null on free Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 2/5] ixgbe: add prefetch to improve slow-path tx perf Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 3/5] testpmd: Change rxfreet default to 32 Bruce Richardson
2014-09-23 17:02     ` Neil Horman
2014-09-24  9:03       ` Richardson, Bruce
2014-09-24 10:05         ` Neil Horman
2014-11-07 12:30         ` Thomas Monjalon
2014-11-07 13:49           ` Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 4/5] mbuf: add userdata pointer field Bruce Richardson
2014-09-23 11:08   ` [dpdk-dev] [PATCH v2 5/5] mbuf: switch vlan_tci and reserved2 fields Bruce Richardson
2014-09-29 15:58   ` [dpdk-dev] [PATCH v2 0/5] Mbuf Structure Rework, part 3 De Lara Guarch, Pablo
2014-10-08 12:31     ` Thomas Monjalon

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