[dpdk-dev] [PATCH v8 2/4] net/i40e: use WC store to update queue tail registers

[Nicolau, Radu]

On 7/20/2020 7:46 AM, Ruifeng Wang wrote:
>> -----Original Message-----
>> From: Radu Nicolau <radu.nicolau at intel.com>
>> Sent: Friday, July 17, 2020 6:50 PM
>> To: dev at dpdk.org
>> Cc: beilei.xing at intel.com; jia.guo at intel.com; bruce.richardson at intel.com;
>> konstantin.ananyev at intel.com; jerinjacobk at gmail.com;
>> david.marchand at redhat.com; fiona.trahe at intel.com; wei.zhao1 at intel.com;
>> Ruifeng Wang <Ruifeng.Wang at arm.com>; Radu Nicolau
>> <radu.nicolau at intel.com>
>> Subject: [PATCH v8 2/4] net/i40e: use WC store to update queue tail registers
>>
>> Performance improvement: use a write combining store instead of a regular
>> mmio write to update queue tail registers.
>>
>> Signed-off-by: Radu Nicolau <radu.nicolau at intel.com>
>> Acked-by: Bruce Richardson <bruce.richardson at intel.com>
>> ---
>>   drivers/net/i40e/base/i40e_osdep.h    | 5 +++++
>>   drivers/net/i40e/i40e_rxtx.c          | 8 ++++----
>>   drivers/net/i40e/i40e_rxtx_vec_avx2.c | 4 ++--
>> drivers/net/i40e/i40e_rxtx_vec_sse.c  | 4 ++--
>>   4 files changed, 13 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/net/i40e/base/i40e_osdep.h
>> b/drivers/net/i40e/base/i40e_osdep.h
>> index 58be396..69ab717 100644
>> --- a/drivers/net/i40e/base/i40e_osdep.h
>> +++ b/drivers/net/i40e/base/i40e_osdep.h
>> @@ -138,6 +138,11 @@ static inline uint32_t i40e_read_addr(volatile void
>> *addr)
>>   #define I40E_PCI_REG_WRITE_RELAXED(reg, value)	\
>>   	rte_write32_relaxed((rte_cpu_to_le_32(value)), reg)
>>
>> +#define I40E_PCI_REG_WC_WRITE(queue, reg, value) \
> 'queue' is not necessary since it will not be used. It can be removed?
Yes, I will remove it - in the first version we had a flag in the queue 
struct, and this macro was not properly updated.
>
> Thanks.
> /Ruifeng
>> +	rte_write32_wc((rte_cpu_to_le_32(value)), reg) #define
>> +I40E_PCI_REG_WC_WRITE_RELAXED(queue, reg, value) \
>> +	rte_write32_wc_relaxed((rte_cpu_to_le_32(value)), reg)
>> +
>>   #define I40E_WRITE_FLUSH(a) I40E_READ_REG(a, I40E_GLGEN_STAT)
>> #define I40EVF_WRITE_FLUSH(a) I40E_READ_REG(a, I40E_VFGEN_RSTAT)
>>
>> diff --git a/drivers/net/i40e/i40e_rxtx.c b/drivers/net/i40e/i40e_rxtx.c index
>> 840b6f3..64e43ac 100644
>> --- a/drivers/net/i40e/i40e_rxtx.c
>> +++ b/drivers/net/i40e/i40e_rxtx.c
>> @@ -760,7 +760,7 @@ i40e_recv_pkts(void *rx_queue, struct rte_mbuf
>> **rx_pkts, uint16_t nb_pkts)
>>   	if (nb_hold > rxq->rx_free_thresh) {
>>   		rx_id = (uint16_t) ((rx_id == 0) ?
>>   			(rxq->nb_rx_desc - 1) : (rx_id - 1));
>> -		I40E_PCI_REG_WRITE(rxq->qrx_tail, rx_id);
>> +		I40E_PCI_REG_WC_WRITE(rxq, rxq->qrx_tail, rx_id);
>>   		nb_hold = 0;
>>   	}
>>   	rxq->nb_rx_hold = nb_hold;
>> @@ -938,7 +938,7 @@ i40e_recv_scattered_pkts(void *rx_queue,
>>   	if (nb_hold > rxq->rx_free_thresh) {
>>   		rx_id = (uint16_t)(rx_id == 0 ?
>>   			(rxq->nb_rx_desc - 1) : (rx_id - 1));
>> -		I40E_PCI_REG_WRITE(rxq->qrx_tail, rx_id);
>> +		I40E_PCI_REG_WC_WRITE(rxq, rxq->qrx_tail, rx_id);
>>   		nb_hold = 0;
>>   	}
>>   	rxq->nb_rx_hold = nb_hold;
>> @@ -1249,7 +1249,7 @@ i40e_xmit_pkts(void *tx_queue, struct rte_mbuf
>> **tx_pkts, uint16_t nb_pkts)
>>   		   (unsigned) tx_id, (unsigned) nb_tx);
>>
>>   	rte_cio_wmb();
>> -	I40E_PCI_REG_WRITE_RELAXED(txq->qtx_tail, tx_id);
>> +	I40E_PCI_REG_WC_WRITE_RELAXED(txq, txq->qtx_tail, tx_id);
>>   	txq->tx_tail = tx_id;
>>
>>   	return nb_tx;
>> @@ -1400,7 +1400,7 @@ tx_xmit_pkts(struct i40e_tx_queue *txq,
>>   		txq->tx_tail = 0;
>>
>>   	/* Update the tx tail register */
>> -	I40E_PCI_REG_WRITE(txq->qtx_tail, txq->tx_tail);
>> +	I40E_PCI_REG_WC_WRITE(txq, txq->qtx_tail, txq->tx_tail);
>>
>>   	return nb_pkts;
>>   }
>> diff --git a/drivers/net/i40e/i40e_rxtx_vec_avx2.c
>> b/drivers/net/i40e/i40e_rxtx_vec_avx2.c
>> index 3bcef13..294c1c4 100644
>> --- a/drivers/net/i40e/i40e_rxtx_vec_avx2.c
>> +++ b/drivers/net/i40e/i40e_rxtx_vec_avx2.c
>> @@ -134,7 +134,7 @@ i40e_rxq_rearm(struct i40e_rx_queue *rxq)
>>   			     (rxq->nb_rx_desc - 1) : (rxq->rxrearm_start - 1));
>>
>>   	/* Update the tail pointer on the NIC */
>> -	I40E_PCI_REG_WRITE(rxq->qrx_tail, rx_id);
>> +	I40E_PCI_REG_WC_WRITE(rxq, rxq->qrx_tail, rx_id);
>>   }
>>
>>   #ifndef RTE_LIBRTE_I40E_16BYTE_RX_DESC
>> @@ -921,7 +921,7 @@ i40e_xmit_fixed_burst_vec_avx2(void *tx_queue,
>> struct rte_mbuf **tx_pkts,
>>
>>   	txq->tx_tail = tx_id;
>>
>> -	I40E_PCI_REG_WRITE(txq->qtx_tail, txq->tx_tail);
>> +	I40E_PCI_REG_WC_WRITE(txq, txq->qtx_tail, txq->tx_tail);
>>
>>   	return nb_pkts;
>>   }
>> diff --git a/drivers/net/i40e/i40e_rxtx_vec_sse.c
>> b/drivers/net/i40e/i40e_rxtx_vec_sse.c
>> index 6985183..a4635e0 100644
>> --- a/drivers/net/i40e/i40e_rxtx_vec_sse.c
>> +++ b/drivers/net/i40e/i40e_rxtx_vec_sse.c
>> @@ -86,7 +86,7 @@ i40e_rxq_rearm(struct i40e_rx_queue *rxq)
>>   			     (rxq->nb_rx_desc - 1) : (rxq->rxrearm_start - 1));
>>
>>   	/* Update the tail pointer on the NIC */
>> -	I40E_PCI_REG_WRITE(rxq->qrx_tail, rx_id);
>> +	I40E_PCI_REG_WC_WRITE(rxq, rxq->qrx_tail, rx_id);
>>   }
>>
>>   #ifndef RTE_LIBRTE_I40E_16BYTE_RX_DESC
>> @@ -733,7 +733,7 @@ i40e_xmit_fixed_burst_vec(void *tx_queue, struct
>> rte_mbuf **tx_pkts,
>>
>>   	txq->tx_tail = tx_id;
>>
>> -	I40E_PCI_REG_WRITE(txq->qtx_tail, txq->tx_tail);
>> +	I40E_PCI_REG_WC_WRITE(txq, txq->qtx_tail, txq->tx_tail);
>>
>>   	return nb_pkts;
>>   }
>> --
>> 2.7.4