netdev - Re: [PATCH v2 4/6] ethtool: support per-queue sub command --show-coalesce

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Date:   Wed, 6 Feb 2019 14:22:28 +0100
From:   Michal Kubecek <mkubecek@...e.cz>
To:     netdev@...r.kernel.org
Cc:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>, linville@...driver.com,
        Nicholas Nunley <nicholas.d.nunley@...el.com>,
        nhorman@...hat.com, sassmann@...hat.com
Subject: Re: [PATCH v2 4/6] ethtool: support per-queue sub command
 --show-coalesce

On Tue, Feb 05, 2019 at 04:01:04PM -0800, Jeff Kirsher wrote:
> diff --git a/ethtool.c b/ethtool.c
> index 4dc725c..9a1b83b 100644
> --- a/ethtool.c
> +++ b/ethtool.c
> @@ -1409,6 +1409,29 @@ static int dump_coalesce(const struct ethtool_coalesce *ecoal)
>  	return 0;
>  }
>  
> +void dump_per_queue_coalesce(struct ethtool_per_queue_op *per_queue_opt,
> +			     __u32 *queue_mask)
> +{
> +	char *addr;
> +	int i;
> +
> +	addr = (char *)per_queue_opt + sizeof(*per_queue_opt);
> +	for (i = 0; i < __KERNEL_DIV_ROUND_UP(MAX_NUM_QUEUE, 32); i++) {
> +		int queue = i * 32;
> +		__u32 mask = queue_mask[i];
> +
> +		while (mask > 0) {
> +			if (mask & 0x1) {
> +				fprintf(stdout, "Queue: %d\n", queue);
> +				dump_coalesce((struct ethtool_coalesce *)addr);
> +				addr += sizeof(struct ethtool_coalesce);
> +			}
> +			mask = mask >> 1;
> +			queue++;
> +		}
> +	}
> +}
> +
>  struct feature_state {
>  	u32 off_flags;
>  	struct ethtool_gfeatures features;

The casts and pointer arithmetic are a bit complicated. How about this?

	struct ethtool_coalesce *addr;
...
	addr = (struct ethtool_coalesce *)(per_queue_opt + 1);
...
	dump_coalesce(addr);
	addr++;

Also passing n_queue down from do_perqueue() would prevent having to
parse the whole bitmap even if we already know the NIC has only few
queues.

> @@ -5245,7 +5268,8 @@ static const struct option {
>  	{ "--show-fec", 1, do_gfec, "Show FEC settings"},
>  	{ "--set-fec", 1, do_sfec, "Set FEC settings",
>  	  "		[ encoding auto|off|rs|baser [...]]\n"},
> -	{ "--set-perqueue-command", 1, do_perqueue, "Set per queue command",
> +	{ "--set-perqueue-command", 1, do_perqueue, "Set per queue command. "
> +	  "The supported sub commands include --show-coalesce",
>  	  "             [queue_mask %x] SUB_COMMAND\n"},
>  	{ "-h|--help", 0, show_usage, "Show this help" },
>  	{ "--version", 0, do_version, "Show version number" },
> @@ -5350,8 +5374,32 @@ static int find_max_num_queues(struct cmd_context *ctx)
>  		   echannels.combined_count);
>  }
>  
> +static struct ethtool_per_queue_op *
> +get_per_queue_coalesce(struct cmd_context *ctx, __u32 *queue_mask, int n_queues)
> +{
> +	struct ethtool_per_queue_op *per_queue_opt;
> +
> +	per_queue_opt = malloc(sizeof(*per_queue_opt) + n_queues *
> +			sizeof(struct ethtool_coalesce));
> +	if (!per_queue_opt)
> +		return NULL;
> +
> +	memcpy(per_queue_opt->queue_mask, queue_mask,
> +	       __KERNEL_DIV_ROUND_UP(MAX_NUM_QUEUE, 32) * sizeof(__u32));
> +	per_queue_opt->cmd = ETHTOOL_PERQUEUE;
> +	per_queue_opt->sub_command = ETHTOOL_GCOALESCE;
> +	if (send_ioctl(ctx, per_queue_opt)) {
> +		free(per_queue_opt);
> +		perror("Cannot get device per queue parameters");
> +		return NULL;
> +	}
> +
> +	return per_queue_opt;
> +}
> +
>  static int do_perqueue(struct cmd_context *ctx)
>  {
> +	struct ethtool_per_queue_op *per_queue_opt;
>  	__u32 queue_mask[__KERNEL_DIV_ROUND_UP(MAX_NUM_QUEUE, 32)] = {0};
>  	int i, n_queues = 0;
>  
> @@ -5390,7 +5438,19 @@ static int do_perqueue(struct cmd_context *ctx)
>  	if (i < 0)
>  		exit_bad_args();
>  
> -	/* no sub_command support yet */
> +	if (strstr(args[i].opts, "--show-coalesce") != NULL) {

Comparing args[i].func to do_gcoalesce might be easier.

> +		per_queue_opt = get_per_queue_coalesce(ctx, queue_mask,
> +						       n_queues);
> +		if (per_queue_opt == NULL) {
> +			perror("Cannot get device per queue parameters");
> +			return -EFAULT;
> +		}
> +		dump_per_queue_coalesce(per_queue_opt, queue_mask);
> +		free(per_queue_opt);
> +	} else {
> +		perror("The subcommand is not supported yet");
> +		return -EOPNOTSUPP;
> +	}
>  
>  	return 0;
>  }

Michal Kubecek