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From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
To: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	"dev@dpdk.org" <dev@dpdk.org>, Phil Yang <Phil.Yang@arm.com>,
	"jgrajcia@cisco.com" <jgrajcia@cisco.com>,
	"ferruh.yigit@intel.com" <ferruh.yigit@intel.com>
Cc: nd <nd@arm.com>, "stable@dpdk.org" <stable@dpdk.org>,
	Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	nd <nd@arm.com>
Subject: Re: [dpdk-stable] [PATCH v2 1/8] net/memif: do not update local copy of tail in tx function
Date: Wed, 7 Oct 2020 17:08:19 +0000
Message-ID: <DBAPR08MB58145A6AA444F7FC2C725527980A0@DBAPR08MB5814.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <20200928190334.40624-1-honnappa.nagarahalli@arm.com>

Hi Jakub,
	Appreciate if you could review this series and provide any comments you might have.

Thank you,
Honnappa

> -----Original Message-----
> From: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Sent: Monday, September 28, 2020 2:03 PM
> To: dev@dpdk.org; Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>;
> Phil Yang <Phil.Yang@arm.com>; jgrajcia@cisco.com; ferruh.yigit@intel.com
> Cc: nd <nd@arm.com>; stable@dpdk.org
> Subject: [PATCH v2 1/8] net/memif: do not update local copy of tail in tx
> function
> 
> In the case of S2M queues, the receiver synchronizes with the sender (i.e.
> informs of the packets it has received) using ring->tail.
> Hence, the sender does not need to update last_tail.
> 
> In the case of M2S queues, the receiver uses last_tail to keep track of the
> descriptors it has received. The sender is not required to update the last_tail.
> Updating the last_tail makes it a shared variable between the transmitter and
> receiver affecting the performance.
> 
> Fixes: 09c7e63a71f9 ("net/memif: introduce memory interface PMD")
> Cc: jgrajcia@cisco.com
> Cc: stable@dpdk.org
> 
> Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Reviewed-by: Phil Yang <phil.yang@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---
>  drivers/net/memif/rte_eth_memif.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/memif/rte_eth_memif.c
> b/drivers/net/memif/rte_eth_memif.c
> index a19c0f3e6..130099f2e 100644
> --- a/drivers/net/memif/rte_eth_memif.c
> +++ b/drivers/net/memif/rte_eth_memif.c
> @@ -580,12 +580,10 @@ eth_memif_tx(void *queue, struct rte_mbuf **bufs,
> uint16_t nb_pkts)
>  	ring_size = 1 << mq->log2_ring_size;
>  	mask = ring_size - 1;
> 
> -	n_free = __atomic_load_n(&ring->tail, __ATOMIC_ACQUIRE) - mq-
> >last_tail;
> -	mq->last_tail += n_free;
> -
>  	if (type == MEMIF_RING_S2M) {
>  		slot = __atomic_load_n(&ring->head, __ATOMIC_ACQUIRE);
> -		n_free = ring_size - slot + mq->last_tail;
> +		n_free = ring_size - slot +
> +				__atomic_load_n(&ring->tail,
> __ATOMIC_ACQUIRE);
>  	} else {
>  		slot = __atomic_load_n(&ring->tail, __ATOMIC_ACQUIRE);
>  		n_free = __atomic_load_n(&ring->head, __ATOMIC_ACQUIRE)
> - slot;
> --
> 2.17.1


  parent reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-21 19:22 [dpdk-stable] [PATCH 1/4] " Honnappa Nagarahalli
2020-09-21 19:22 ` [dpdk-stable] [PATCH 2/4] net/memif: relax the load of ring tail pointer for M2S ring Honnappa Nagarahalli
2020-09-21 19:22 ` [dpdk-stable] [PATCH 3/4] net/memif: relax the load of ring head pointer for S2M ring Honnappa Nagarahalli
2020-09-21 19:22 ` [dpdk-stable] [PATCH 4/4] net/memif: relax the load of ring head pointer for M2S ring Honnappa Nagarahalli
2020-09-28 19:03 ` [dpdk-stable] [PATCH v2 1/8] net/memif: do not update local copy of tail in tx function Honnappa Nagarahalli
2020-09-28 19:03   ` [dpdk-stable] [PATCH v2 2/8] net/memif: relax the load of ring tail pointer for M2S ring Honnappa Nagarahalli
2020-09-28 19:03   ` [dpdk-stable] [PATCH v2 3/8] net/memif: relax the load of ring head " Honnappa Nagarahalli
2020-09-28 19:03   ` [dpdk-stable] [PATCH v2 4/8] net/memif: relax the load of ring head pointer for S2M ring Honnappa Nagarahalli
2020-09-28 20:53   ` [dpdk-stable] [dpdk-dev] [PATCH v2 1/8] net/memif: do not update local copy of tail in tx function Stephen Hemminger
2020-09-29  5:24     ` Honnappa Nagarahalli
2020-10-07 17:08   ` Honnappa Nagarahalli [this message]
2020-10-09 11:23     ` [dpdk-stable] " Jakub Grajciar -X (jgrajcia - PANTHEON TECH SRO at Cisco)
2020-10-09 15:59       ` Ferruh Yigit

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