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Date: Thu, 26 Mar 2020 01:53:07 +0300
From: Slawa Olhovchenkov <slw@zxy.spb.ru>
To: Vincenzo Maffione <vmaffione@freebsd.org>
Cc: Alexandre Snarskii <snar@snar.spb.ru>,
 "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>
Subject: Re: netmap/ixl and crc addition..
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On Wed, Mar 25, 2020 at 11:31:30PM +0100, Vincenzo Maffione wrote:

> Hi Alexandre,
>   Thanks. Your patch looks good to me. I assume you have tested it?
> I will commit that to stable/11.
> 
> The issue you report on stable/12 is more worrisome. The 'no space in TX
> ring' condition (head==cur==tail) is ok per-se: on a subsequent poll()
> wakeup (e.g. TX interrupt) or explicit ioctl(NIOCTXSYNC) you should see
> tail moving forward, therefore freeing some space to be used in the ring.
> However, the ring_reinit means that something is going wrong: either your
> application is using the TX ring incorrectly, or there is a bug in the
> netmap iflib code. Since FreeBSD 12, netmap support is provided by iflib,
> while before netmap support was provided directly by the ixl driver.
> In any case, it would probably help if you could provide some more detailed
> info (how to reproduce the problem).

Just run pkt-gen for transmit. The conditions is guaranteed to occur
(for me, at least).