[PATCH] examples/l3fwd: add option to set RX burst size

[Morten Brørup]

> From: Jie Hai [mailto:haijie1 at huawei.com]
> Sent: Saturday, 12 October 2024 10.41
> 
> Now the Rx burst size is fixed to MAX_PKT_BURST (32). This
> parameter needs to be modified in some performance optimization
> scenarios. So an option '--burst' is added to set the burst size
> explicitly. The default value is DEFAULT_PKT_BURST (32) and maximum
> value is MAX_PKT_BURST (512).

Good idea.

> 
> Signed-off-by: Jie Hai <haijie1 at huawei.com>
> ---
> 
> -#define MAX_PKT_BURST     32
> +#define DEFAULT_PKT_BURST 32
> +#define MAX_PKT_BURST 512
>  #define BURST_TX_DRAIN_US 100 /* TX drain every ~100us */
> 
>  #define MEMPOOL_CACHE_SIZE 256

It seems strange to use a burst size larger than the mempool cache size.

You might want to make the cache size configurable too, or simply define MEMPOOL_CACHE_SIZE as RTE_MEMPOOL_CACHE_MAX_SIZE (currently 512) instead of 256.

And, as a safety measure, consider adding:
#include <assert.h>
static_assert(MEMPOOL_CACHE_SIZE >= MAX_PKT_BURST);