[PATCH] examples/l3fwd: fix Tx performance deteriorate

[Jie Hai]

Hi, konstantin.ananyev,

That sounds better, will send V2。

Thanks,
Jie Hai

> 
> In  commit:
> examples/l3fwd: add option to set Rx burst size
> you introduced new global
> uint32_t nb_pkt_per_burst;
> Why not to use it for both (rx and tx) paths?
> Or if necessary introduce another one for tx, so we'll have:
> uint32_t nb_rx_pkt_per_burst, nb_tx_pkt_per_burst,;
> To me that is much better then create some hardcoded
> and implicit thresholds.
> 
>> Fixes: d5c4897ecfb2 ("examples/l3fwd: add option to set Rx burst size")
>>
>> Signed-off-by: Jie Hai <haijie1 at huawei.com>
>> ---
>>   examples/l3fwd/l3fwd.h        | 8 +++++---
>>   examples/l3fwd/l3fwd_common.h | 6 +++---
>>   2 files changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/examples/l3fwd/l3fwd.h b/examples/l3fwd/l3fwd.h
>> index 0cce3406ee7d..a01fecd51261 100644
>> --- a/examples/l3fwd/l3fwd.h
>> +++ b/examples/l3fwd/l3fwd.h
>> @@ -35,7 +35,7 @@
>>   /*
>>    * Try to avoid TX buffering if we have at least MAX_TX_BURST packets to send.
>>    */
>> -#define	MAX_TX_BURST	  (MAX_PKT_BURST / 2)
>> +#define	MAX_TX_BURST DEFAULT_PKT_BURST
>>
>>   #define NB_SOCKETS        8
>>
>> @@ -57,6 +57,8 @@
>>   #define L3FWD_HASH_ENTRIES		(1024*1024*1)
>>   #endif
>>
>> +static_assert(MAX_TX_BURST <= MAX_PKT_BURST, "MAX_TX_BURST should be at most MAX_PKT_BURST");
>> +
>>   struct parm_cfg {
>>   	const char *rule_ipv4_name;
>>   	const char *rule_ipv6_name;
>> @@ -152,8 +154,8 @@ send_single_packet(struct lcore_conf *qconf,
>>   	len++;
>>
>>   	/* enough pkts to be sent */
>> -	if (unlikely(len == MAX_PKT_BURST)) {
>> -		send_burst(qconf, MAX_PKT_BURST, port);
>> +	if (unlikely(len == MAX_TX_BURST)) {
>> +		send_burst(qconf, MAX_TX_BURST, port);
>>   		len = 0;
>>   	}
>>
>> diff --git a/examples/l3fwd/l3fwd_common.h b/examples/l3fwd/l3fwd_common.h
>> index d94e5f135791..3f504dc0a552 100644
>> --- a/examples/l3fwd/l3fwd_common.h
>> +++ b/examples/l3fwd/l3fwd_common.h
>> @@ -71,7 +71,7 @@ send_packetsx4(struct lcore_conf *qconf, uint16_t port, struct rte_mbuf *m[],
>>   	 * If TX buffer for that queue is empty, and we have enough packets,
>>   	 * then send them straightway.
>>   	 */
>> -	if (num >= MAX_TX_BURST && len == 0) {
>> +	if (num >= MAX_TX_BURST / 2 && len == 0) {
>>   		n = rte_eth_tx_burst(port, qconf->tx_queue_id[port], m, num);
>>   		if (unlikely(n < num)) {
>>   			do {
>> @@ -112,9 +112,9 @@ send_packetsx4(struct lcore_conf *qconf, uint16_t port, struct rte_mbuf *m[],
>>   	len += n;
>>
>>   	/* enough pkts to be sent */
>> -	if (unlikely(len == MAX_PKT_BURST)) {
>> +	if (unlikely(len > MAX_TX_BURST)) {
>>
>> -		send_burst(qconf, MAX_PKT_BURST, port);
>> +		send_burst(qconf, len, port);
>>
>>   		/* copy rest of the packets into the TX buffer. */
>>   		len = num - n;
>> --
>> 2.22.0
>