Re: [dpdk-dev] [PATCH v3] ixgbe: remove vector pmd burst size restriction

[Zoltan Kiss <zoltan.kiss@linaro.org>]

On 05/08/15 07:28, Liang, Cunming wrote:
> Hi Zoltan,
>
>> -----Original Message-----
>> From: Zoltan Kiss [mailto:zoltan.kiss@linaro.org]
>> Sent: Wednesday, August 05, 2015 12:26 AM
>> To: Liang, Cunming; dev@dpdk.org
>> Cc: Ananyev, Konstantin
>> Subject: Re: [PATCH v3] ixgbe: remove vector pmd burst size restriction
>>
>>
>>
>> On 04/08/15 12:47, Cunming Liang wrote:
>>> On receive side, the burst size now floor aligns to RTE_IXGBE_DESCS_PER_LOOP
>> power of 2.
>>> According to this rule, the burst size less than 4 still won't receive anything.
>>> (Before this change, the burst size less than 32 can't receive anything.)
>>> _recv_*_pkts_vec returns no more than 32(RTE_IXGBE_RXQ_REARM_THRESH)
>> packets.
>>>
>>> On transmit side, the max burst size no longer bind with a constant, however it
>> still
>>> require to check the cross tx_rs_thresh violation.
>>>
>>> There's no obvious performance drop found on both recv_pkts_vec
>>> and recv_scattered_pkts_vec on burst size 32.
>>>
>>> Signed-off-by: Cunming Liang <cunming.liang@intel.com>
>>> ---
>>>    v3 change:
>>>     - reword the init print log
>>>
>>>    v2 change:
>>>     - keep max rx burst size in 32
>>>     - reword some comments
>>>
>>>    drivers/net/ixgbe/ixgbe_rxtx.c     |  4 +++-
>>>    drivers/net/ixgbe/ixgbe_rxtx.h     |  5 ++---
>>>    drivers/net/ixgbe/ixgbe_rxtx_vec.c | 39
>> +++++++++++++++++++++-----------------
>>>    3 files changed, 27 insertions(+), 21 deletions(-)
>>>
>>> diff --git a/drivers/net/ixgbe/ixgbe_rxtx.c b/drivers/net/ixgbe/ixgbe_rxtx.c
>>> index 91023b9..03eb45d 100644
>>> --- a/drivers/net/ixgbe/ixgbe_rxtx.c
>>> +++ b/drivers/net/ixgbe/ixgbe_rxtx.c
>>> @@ -4008,7 +4008,9 @@ ixgbe_set_rx_function(struct rte_eth_dev *dev)
>>>    	 */
>>>    	} else if (adapter->rx_vec_allowed) {
>>>    		PMD_INIT_LOG(DEBUG, "Vector rx enabled, please make sure RX "
>>> -				   "burst size no less than 32.");
>>> +				    "burst size no less than %d (port=%d).",
>>> +			     RTE_IXGBE_DESCS_PER_LOOP,
>>> +			     dev->data->port_id);
>>
>> A tab seems to be missing from the indentation, otherwise:
>>
>> Reviewed-by: Zoltan Kiss <zoltan.kiss@linaro.org>
>>
> Thanks for the review. I double checked indentation agian, it looks fine.
> 1st string line 4x/tab intention + space alignment, the other variable lines 3x/tab indentation + space alignment.
> According to the 'coding_style.rst' Indentation section - 'As with all style guideline, code should match style already in use in an existing file.'
> The style keeps the same as its following condition check. It passes 'checkpatch.pl' checking as well.

Sorry for the noise, I was confused because the string is indented to 
the start of itself, while the other parameters to the opening bracket.
>
> Thanks,
> /Steve
>>>
>>>    		dev->rx_pkt_burst = ixgbe_recv_pkts_vec;
>>>    	} else if (adapter->rx_bulk_alloc_allowed) {
>>> diff --git a/drivers/net/ixgbe/ixgbe_rxtx.h b/drivers/net/ixgbe/ixgbe_rxtx.h
>>> index 113682a..b9eca67 100644
>>> --- a/drivers/net/ixgbe/ixgbe_rxtx.h
>>> +++ b/drivers/net/ixgbe/ixgbe_rxtx.h
>>> @@ -47,9 +47,8 @@
>>>    	(uint64_t) ((mb)->buf_physaddr + RTE_PKTMBUF_HEADROOM)
>>>
>>>    #ifdef RTE_IXGBE_INC_VECTOR
>>> -#define RTE_IXGBE_VPMD_RX_BURST         32
>>> -#define RTE_IXGBE_VPMD_TX_BURST         32
>>> -#define RTE_IXGBE_RXQ_REARM_THRESH      RTE_IXGBE_VPMD_RX_BURST
>>> +#define RTE_IXGBE_RXQ_REARM_THRESH      32
>>> +#define RTE_IXGBE_MAX_RX_BURST
>> RTE_IXGBE_RXQ_REARM_THRESH
>>>    #define RTE_IXGBE_TX_MAX_FREE_BUF_SZ    64
>>>    #endif
>>>
>>> diff --git a/drivers/net/ixgbe/ixgbe_rxtx_vec.c
>> b/drivers/net/ixgbe/ixgbe_rxtx_vec.c
>>> index cf25a53..2ca0e4c 100644
>>> --- a/drivers/net/ixgbe/ixgbe_rxtx_vec.c
>>> +++ b/drivers/net/ixgbe/ixgbe_rxtx_vec.c
>>> @@ -245,13 +245,13 @@ desc_to_olflags_v(__m128i descs[4], struct
>> rte_mbuf **rx_pkts)
>>>    #endif
>>>
>>>    /*
>>> - * vPMD receive routine, now only accept (nb_pkts ==
>> RTE_IXGBE_VPMD_RX_BURST)
>>> - * in one loop
>>> + * vPMD raw receive routine, only accept(nb_pkts >=
>> RTE_IXGBE_DESCS_PER_LOOP)
>>>     *
>>>     * Notice:
>>> - * - nb_pkts < RTE_IXGBE_VPMD_RX_BURST, just return no packet
>>> - * - nb_pkts > RTE_IXGBE_VPMD_RX_BURST, only scan
>> RTE_IXGBE_VPMD_RX_BURST
>>> + * - nb_pkts < RTE_IXGBE_DESCS_PER_LOOP, just return no packet
>>> + * - nb_pkts > RTE_IXGBE_MAX_RX_BURST, only scan
>> RTE_IXGBE_MAX_RX_BURST
>>>     *   numbers of DD bit
>>> + * - floor align nb_pkts to a RTE_IXGBE_DESC_PER_LOOP power-of-two
>>>     * - don't support ol_flags for rss and csum err
>>>     */
>>>    static inline uint16_t
>>> @@ -286,8 +286,11 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq,
>> struct rte_mbuf **rx_pkts,
>>>    	__m128i dd_check, eop_check;
>>>    #endif /* RTE_NEXT_ABI */
>>>
>>> -	if (unlikely(nb_pkts < RTE_IXGBE_VPMD_RX_BURST))
>>> -		return 0;
>>> +	/* nb_pkts shall be less equal than RTE_IXGBE_MAX_RX_BURST */
>>> +	nb_pkts = RTE_MIN(nb_pkts, RTE_IXGBE_MAX_RX_BURST);
>>> +
>>> +	/* nb_pkts has to be floor-aligned to RTE_IXGBE_DESCS_PER_LOOP */
>>> +	nb_pkts = RTE_ALIGN_FLOOR(nb_pkts, RTE_IXGBE_DESCS_PER_LOOP);
>>>
>>>    	/* Just the act of getting into the function from the application is
>>>    	 * going to cost about 7 cycles */
>>> @@ -356,7 +359,7 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq,
>> struct rte_mbuf **rx_pkts,
>>>    	 * D. fill info. from desc to mbuf
>>>    	 */
>>>    #endif /* RTE_NEXT_ABI */
>>> -	for (pos = 0, nb_pkts_recd = 0; pos < RTE_IXGBE_VPMD_RX_BURST;
>>> +	for (pos = 0, nb_pkts_recd = 0; pos < nb_pkts;
>>>    			pos += RTE_IXGBE_DESCS_PER_LOOP,
>>>    			rxdp += RTE_IXGBE_DESCS_PER_LOOP) {
>>>    #ifdef RTE_NEXT_ABI
>>> @@ -518,13 +521,13 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq,
>> struct rte_mbuf **rx_pkts,
>>>    }
>>>
>>>    /*
>>> - * vPMD receive routine, now only accept (nb_pkts ==
>> RTE_IXGBE_VPMD_RX_BURST)
>>> - * in one loop
>>> + * vPMD receive routine, only accept(nb_pkts >=
>> RTE_IXGBE_DESCS_PER_LOOP)
>>>     *
>>>     * Notice:
>>> - * - nb_pkts < RTE_IXGBE_VPMD_RX_BURST, just return no packet
>>> - * - nb_pkts > RTE_IXGBE_VPMD_RX_BURST, only scan
>> RTE_IXGBE_VPMD_RX_BURST
>>> + * - nb_pkts < RTE_IXGBE_DESCS_PER_LOOP, just return no packet
>>> + * - nb_pkts > RTE_IXGBE_MAX_RX_BURST, only scan
>> RTE_IXGBE_MAX_RX_BURST
>>>     *   numbers of DD bit
>>> + * - floor align nb_pkts to a RTE_IXGBE_DESC_PER_LOOP power-of-two
>>>     * - don't support ol_flags for rss and csum err
>>>     */
>>>    uint16_t
>>> @@ -538,12 +541,11 @@ static inline uint16_t
>>>    reassemble_packets(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_bufs,
>>>    		uint16_t nb_bufs, uint8_t *split_flags)
>>>    {
>>> -	struct rte_mbuf *pkts[RTE_IXGBE_VPMD_RX_BURST]; /*finished pkts*/
>>> +	struct rte_mbuf *pkts[nb_bufs]; /*finished pkts*/
>>>    	struct rte_mbuf *start = rxq->pkt_first_seg;
>>>    	struct rte_mbuf *end =  rxq->pkt_last_seg;
>>>    	unsigned pkt_idx, buf_idx;
>>>
>>> -
>>>    	for (buf_idx = 0, pkt_idx = 0; buf_idx < nb_bufs; buf_idx++) {
>>>    		if (end != NULL) {
>>>    			/* processing a split packet */
>>> @@ -603,14 +605,17 @@ reassemble_packets(struct ixgbe_rx_queue *rxq,
>> struct rte_mbuf **rx_bufs,
>>>     *
>>>     * Notice:
>>>     * - don't support ol_flags for rss and csum err
>>> - * - now only accept (nb_pkts == RTE_IXGBE_VPMD_RX_BURST)
>>> + * - nb_pkts < RTE_IXGBE_DESCS_PER_LOOP, just return no packet
>>> + * - nb_pkts > RTE_IXGBE_MAX_RX_BURST, only scan
>> RTE_IXGBE_MAX_RX_BURST
>>> + *   numbers of DD bit
>>> + * - floor align nb_pkts to a RTE_IXGBE_DESC_PER_LOOP power-of-two
>>>     */
>>>    uint16_t
>>>    ixgbe_recv_scattered_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts,
>>>    		uint16_t nb_pkts)
>>>    {
>>>    	struct ixgbe_rx_queue *rxq = rx_queue;
>>> -	uint8_t split_flags[RTE_IXGBE_VPMD_RX_BURST] = {0};
>>> +	uint8_t split_flags[RTE_IXGBE_MAX_RX_BURST] = {0};
>>>
>>>    	/* get some new buffers */
>>>    	uint16_t nb_bufs = _recv_raw_pkts_vec(rxq, rx_pkts, nb_pkts,
>>> @@ -735,8 +740,8 @@ ixgbe_xmit_pkts_vec(void *tx_queue, struct rte_mbuf
>> **tx_pkts,
>>>    	uint64_t rs = IXGBE_ADVTXD_DCMD_RS|DCMD_DTYP_FLAGS;
>>>    	int i;
>>>
>>> -	if (unlikely(nb_pkts > RTE_IXGBE_VPMD_TX_BURST))
>>> -		nb_pkts = RTE_IXGBE_VPMD_TX_BURST;
>>> +	/* cross rx_thresh boundary is not allowed */
>>> +	nb_pkts = RTE_MIN(nb_pkts, txq->tx_rs_thresh);
>>>
>>>    	if (txq->nb_tx_free < txq->tx_free_thresh)
>>>    		ixgbe_tx_free_bufs(txq);
>>>