From: Eric Dumazet <eric.dumazet@gmail.com>
To: Andrew Gallatin <gallatin@myri.com>
Cc: netdev <netdev@vger.kernel.org>
Subject: Re: gro vs vlan in myri10ge
Date: Thu, 08 Nov 2012 18:41:10 -0800 [thread overview]
Message-ID: <1352428870.19779.496.camel@edumazet-glaptop> (raw)
In-Reply-To: <509C6858.6010105@myri.com>
On Thu, 2012-11-08 at 21:20 -0500, Andrew Gallatin wrote:
> Hi,
>
> I've wanted to convert myri10ge from LRO to GRO for quite a while.
> The problem I'm facing is that the NIC cannot perform hardware vlan
> tag offload, so GRO performance is far below LRO performance when
> receiving vlan tagged TCP traffic.
>
> If a vlan tagged frame is passed to lro_receive_frags(), inet_lro will
> look at the encapsulated IPv4 frame and TCP aggregation will succeed.
> However, it appears that GRO will not do this. When I patch the
> driver to use GRO, and configure a vlan interface, I see high CPU
> utilization and poor bandwidth when I'm receiving a netperf TCP stream
> on the vlan interface. If I use LRO in an unpatched driver, then I
> see good receive performance in the same scenario.
>
> What is the best way to "fix" this?
>
> Unless I'm just using GRO wrong, it seems that the simplest thing for
> me to do is to claim NETIF_F_HW_VLAN_RX, but pop the tags in the
> driver so as to allow myri10ge to pass up a non-encapsulated frame the
> same way that (nearly?) every other 10GbE NIC does. I've got a quick
> and dirty patch that confirms doing the vtag pop in the driver gives
> me roughly the same performance with GRO as I used to have with LRO.
>
> Is this (popping vlan tags in the driver) acceptable, or is it
> too much of a layering violation?
Given GRO assumes NIC does hardware vlan offloading, I guess
I would chose to do that.
It seems unfortunate to add vlan decap in GRO path, already very
complex.
next prev parent reply other threads:[~2012-11-09 2:41 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-09 2:20 gro vs vlan in myri10ge Andrew Gallatin
2012-11-09 2:41 ` Eric Dumazet [this message]
2012-11-09 12:47 ` Andrew Gallatin
2012-11-15 20:39 ` Ben Hutchings
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1352428870.19779.496.camel@edumazet-glaptop \
--to=eric.dumazet@gmail.com \
--cc=gallatin@myri.com \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox