Re: [dpdk-dev] [PATCH] examples/multi_process: fix buffer underrun

[Bruce Richardson <bruce.richardson@intel.com>]

On Tue, Apr 09, 2019 at 03:59:37PM -0700, Yongseok Koh wrote:
> For client_server_mp, the total number of buffers for the mbuf mempool
> should be correctly calculated. Otherwise, having more clients will stop
> traffic.
> 
> Fixes: af75078fece3 ("first public release")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
> ---
>  examples/multi_process/client_server_mp/mp_server/init.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/examples/multi_process/client_server_mp/mp_server/init.c b/examples/multi_process/client_server_mp/mp_server/init.c
> index 30c8e44bc0..0491ba8a1a 100644
> --- a/examples/multi_process/client_server_mp/mp_server/init.c
> +++ b/examples/multi_process/client_server_mp/mp_server/init.c
> @@ -37,8 +37,6 @@
>  #include "args.h"
>  #include "init.h"
>  
> -#define MBUFS_PER_CLIENT 1536
> -#define MBUFS_PER_PORT 1536
>  #define MBUF_CACHE_SIZE 512
>  
>  #define RTE_MP_RX_DESC_DEFAULT 1024
> @@ -63,8 +61,12 @@ struct port_info *ports;
>  static int
>  init_mbuf_pools(void)
>  {
> -	const unsigned num_mbufs = (num_clients * MBUFS_PER_CLIENT) \
> -			+ (ports->num_ports * MBUFS_PER_PORT);
> +	const unsigned int num_mbufs =
> +		RTE_MP_RX_DESC_DEFAULT * ports->num_ports + /* Sever */

typo: server

> +		num_clients *
> +		(CLIENT_QUEUE_RINGSIZE +
> +		 RTE_MP_TX_DESC_DEFAULT * ports->num_ports) + /* Clients */
> +		(num_clients + 1) * MBUF_CACHE_SIZE; /* Mempool cache */
>  

The calculation looks correct to me, it's just rather long with strange
wrapping. I'd suggest either splitting up the calculation to have a
separate variable for per-client mbuf counts, or else just use a longer
line for readability for the client calculation.

>  	/* don't pass single-producer/single-consumer flags to mbuf create as it
>  	 * seems faster to use a cache instead */
> -- 
> 2.11.0
>