From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Monjalon <thomas.monjalon@6wind.com>
Subject: Re: [PATCH 6/6] examples/vhost: add an option to enable
	Tx zero copy
Date: Tue, 23 Aug 2016 11:31:08 +0200
Message-ID: <2052249.1FX31XPDFZ@xps13>
References: <1471939839-29778-1-git-send-email-yuanhan.liu@linux.intel.com>
 <1471939839-29778-7-git-send-email-yuanhan.liu@linux.intel.com>
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Cc: dev@dpdk.org, Maxime Coquelin <maxime.coquelin@redhat.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
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2016-08-23 16:10, Yuanhan Liu:
> One thing worth noting while using Tx zero copy is the nb_tx_desc has
> to be small enough so that the eth driver will hit the mbuf free
> threshold easily and thus free mbuf more frequently.
> 
> The reason behind that is, when Tx zero copy is enabled, guest Tx used
> vring will be updated only when corresponding mbuf is freed. If mbuf is
> not freed frequently, the guest Tx vring could be starved.

I think you should explain this behaviour in the doc of the vhost flag.