From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [PATCH v6] net/tap: fix missing _SC_IOV_MAX
Date: Mon, 18 Mar 2019 10:56:36 -0700
Message-ID: <20190318105636.2a96f3ab@shemminger-XPS-13-9360>
References: <20190318165523.4086-1-olegp123@walla.co.il>
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Cc: keith.wiles@intel.com, thomas@monjalon.net, dev@dpdk.org, stable@dpdk.org
To: olegpoly123 <olegp123@walla.co.il>
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On Mon, 18 Mar 2019 12:55:23 -0400
olegpoly123 <olegp123@walla.co.il> wrote:

>  	long iov_max = sysconf(_SC_IOV_MAX);
> +
> +	if (iov_max <= 0) {
> +		TAP_LOG(WARNING,
> +			"_SC_IOV_MAX is not defined. Using %d as default\n",
> +			TAP_IOV_DEFAULT_MAX);
> +		iov_max = TAP_IOV_DEFAULT_MAX;
> +	}
>  	uint16_t nb_desc = RTE_MIN(nb_rx_desc, iov_max - 1);

Looking at this a little more carefully.

1. Trivial: TAP_LOG() already adds a newline.

2. TAP device should not be silently reducing the number of receive descriptors.

3. TAP device be using IOV_MAX to set rx_descriptor limit. (in dev_info)
   The ethdev would rx_queue_setup with any request for too large a value.