From: Adrien Mazarguil <adrien.mazarguil@6wind.com>
To: Luke Gorrie <luke@snabb.co>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: Possible bug in mlx5_tx_burst_mpw?
Date: Wed, 14 Sep 2016 16:30:34 +0200 [thread overview]
Message-ID: <20160914143016.GT17252@6wind.com> (raw)
In-Reply-To: <CAA2XHbd+c2vuFKu7CivDkAG+1KEhq28yKd+-GsJjMVukS-2CxA@mail.gmail.com>
Hi Luke,
On Wed, Sep 14, 2016 at 03:24:07PM +0200, Luke Gorrie wrote:
> Howdy,
>
> Just noticed a line of code that struck me as odd and so I am writing just
> in case it is a bug:
>
> http://dpdk.org/browse/dpdk/tree/drivers/net/mlx5/mlx5_rxtx.c#n1014
>
> Specifically the check "(mpw.length != length)" in mlx_tx_burst_mpw() looks
> like a descriptor-format optimization for the special case where
> consecutive packets on the wire are exactly the same size. This would
> strike me as peculiar.
>
> Just wanted to check, is that interpretation correct and if so then is this
> intentional?
Your interpretation is correct (this is intentional and not a bug).
In the event successive packets share a few properties (length, number of
segments, offload flags), these can be factored out as an optimization to
lower the amount of traffic on the PCI bus. This feature is currently
supported by the ConnectX-4 Lx family of adapters.
--
Adrien Mazarguil
6WIND
next prev parent reply other threads:[~2016-09-14 14:30 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-14 13:24 Possible bug in mlx5_tx_burst_mpw? Luke Gorrie
2016-09-14 14:30 ` Adrien Mazarguil [this message]
2016-09-14 19:33 ` Luke Gorrie
2016-09-16 7:14 ` Adrien Mazarguil
2016-09-16 7:57 ` Luke Gorrie
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