Re: [dpdk-dev] [PATCH] net/mlx5: use open/read/close for reading ib stat

[Raslan Darawsheh <rasland@mellanox.com>]

Hi,


> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Mohsin Shaikh
> Sent: Thursday, April 9, 2020 11:37 PM
> To: dev@dpdk.org
> Cc: stable@dpdk.org; Alexander Kozyrev <akozyrev@mellanox.com>;
> Mohsin Shaikh <mohsinshaikh@niometrics.com>
> Subject: [dpdk-dev] [PATCH] net/mlx5: use open/read/close for reading ib
> stat
> 
> fgets(3)/fread(3)/fscanf(3) etc. use mmap(2)/munmap(2) which leads
> to TLB shootdown interrupts to all dpdk app cores including RX cores.
> This can cause packet drops. Use read(2)/write(2) instead.
> 
> Bugzilla ID: 440
> Cc: stable@dpdk.org
> 
> Signed-off-by: Mohsin Shaikh <mohsinshaikh@niometrics.com>
> ---
>  drivers/net/mlx5/mlx5_stats.c | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/mlx5/mlx5_stats.c b/drivers/net/mlx5/mlx5_stats.c
> index 7603502..b2c09d8 100644
> --- a/drivers/net/mlx5/mlx5_stats.c
> +++ b/drivers/net/mlx5/mlx5_stats.c
> @@ -3,11 +3,13 @@
>   * Copyright 2015 Mellanox Technologies, Ltd
>   */
> 
> +#include <fcntl.h>
>  #include <inttypes.h>
>  #include <linux/sockios.h>
>  #include <linux/ethtool.h>
>  #include <stdint.h>
>  #include <stdio.h>
> +#include <unistd.h>
> 
>  #include <rte_ethdev_driver.h>
>  #include <rte_common.h>
> @@ -142,20 +144,23 @@
>  static inline void
>  mlx5_read_ib_stat(struct mlx5_priv *priv, const char *ctr_name, uint64_t
> *stat)
>  {
> -	FILE *file;
> +	int fd;
> +
>  	if (priv->sh) {
>  		MKSTR(path, "%s/ports/%d/hw_counters/%s",
>  			  priv->sh->ibdev_path,
>  			  priv->ibv_port,
>  			  ctr_name);
> -
> -		file = fopen(path, "rb");
> -		if (file) {
> -			int n = fscanf(file, "%" SCNu64, stat);
> -
> -			fclose(file);
> -			if (n == 1)
> +		fd = open(path, O_RDONLY);
> +		if (fd != -1) {
> +			char buf[21] = {'\0'};
> +			ssize_t n = read(fd, buf, sizeof(buf));
> +
> +			close(fd);
> +			if (n != -1) {
> +				*stat = strtoull(buf, NULL, 10);
>  				return;
> +			}
>  		}
>  	}
>  	*stat = 0;
> --
> 1.8.3.1


Patch rebased and applied to next-net-mlx,

Kindest regards
Raslan Darawsheh