> The application send packets only when the buffer is full, or the
> buffer is empty and the number of packets to be sent extends half
> of the buffer.
>
> The change of MAX_PKT_BURST increases TX buffer size, while the
> default size of local cache on each lcore is 256, which not greater
> than the limit of transmitting. That would make the mbuf not on the
> local cache be frequently used and the performance deteriorates.
>
> This problem can be solved by making the TX threshold smaller than
> the local cache size. For example, use the '--mbcache' parameter to
> make the local cache greater. This patch optimizes the default
> performance by lowering TX threshold.
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 <haij...@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
