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From: Tiwei Bie <tiwei.bie@intel.com>
To: Andrew Rybchenko <arybchenko@solarflare.com>
Cc: David Marchand <david.marchand@redhat.com>,
	Thomas Monjalon <thomas@monjalon.net>,
	Ferruh Yigit <ferruh.yigit@intel.com>,
	Maxime Coquelin <maxime.coquelin@redhat.com>,
	Zhihong Wang <zhihong.wang@intel.com>, dev <dev@dpdk.org>,
	Dilshod Urazov <Dilshod.Urazov@oktetlabs.ru>
Subject: Re: [dpdk-dev] [PATCH 3/3] net/virtio: reject unsupported Rx multi queue modes
Date: Thu, 10 Oct 2019 17:10:20 +0800
Message-ID: <20191010091020.GA5729@___> (raw)
In-Reply-To: <e8aa95fe-a422-cf5a-c505-f6c240068e9a@solarflare.com>

On Thu, Oct 10, 2019 at 11:27:53AM +0300, Andrew Rybchenko wrote:
> On 10/10/19 11:23 AM, David Marchand wrote:
> > On Thu, Oct 10, 2019 at 10:14 AM Andrew Rybchenko
> > <arybchenko@solarflare.com> wrote:
> > > On 10/10/19 10:42 AM, Thomas Monjalon wrote:
> > > > 09/10/2019 13:24, Andrew Rybchenko:
> > > > > On 10/9/19 1:41 PM, Tiwei Bie wrote:
> > > > > > My understanding is that, setting mq_mode to ETH_MQ_RX_NONE means
> > > > > > no method is enforced on how to route packets to MQs.
> > > > > I'm not sure. It is definitely a place to be improved in
> > > > > ethdev documentation. Thomas, Ferruh, what do you think?
> > > > > Is it really a definition of ETH_MQ_RX_NONE?
> > > > I think it means everything go to queue 0.
> > > I understand it this way as well.
> > > 
> > > > The comment says no DCB, RSS or VMDQ.
> > > > It looks like the "NONE" value has been abused for some custom steering.
> > > > We have two options:
> > > >        - document NONE as a possible case of custom steering
> > > >        - add a new CUSTOM value
> > > I'd prefer to say that ETH_MQ_RX_RSS with rss_hf equal to 0 means
> > > unspecified/unknown steering. If application just want to spread
> > > traffic across many Rx queues, it is natural choice to say that
> > > it want RSS, but do not care about spreading algorithm etc.
> > > It allows driver use recommended defaults if rss_hf is controllable,
> > > or just spread in virtio case.
> > RSS is about maintaining affinity of a "flow" (as in packets sharing
> > the same l3/l4 tuples) to a specific queue.
> > Here, we can have packets from a same flow on any queue depending on
> > what happened on the vhost side.
> 
> Interesting. I'd like to know a bit more about it. I didn't know that
> it is so unstable. Could someone who knows the topic well add
> a bit more information about it.

The spec defined automatic steering [1], but it's not very strict
for the device. So it depends on the implementation.

[1] https://github.com/oasis-tcs/virtio-spec/commit/f7020384521e5938cdd1351270b32b143f070d00


  reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-01 15:44 [dpdk-dev] [PATCH 1/3] net/virtio: reject deferred start Rx queue setup Andrew Rybchenko
2019-10-01 15:44 ` [dpdk-dev] [PATCH 2/3] net/virtio: reject deferred start Tx " Andrew Rybchenko
2019-10-08  5:35   ` Tiwei Bie
2019-10-01 15:44 ` [dpdk-dev] [PATCH 3/3] net/virtio: reject unsupported Rx multi queue modes Andrew Rybchenko
2019-10-08  5:46   ` Tiwei Bie
2019-10-09  8:04     ` Andrew Rybchenko
2019-10-09  8:43       ` Tiwei Bie
2019-10-09  9:00         ` Andrew Rybchenko
2019-10-09 10:41           ` Tiwei Bie
2019-10-09 11:24             ` Andrew Rybchenko
2019-10-10  7:42               ` Thomas Monjalon
2019-10-10  8:13                 ` Andrew Rybchenko
2019-10-10  8:23                   ` David Marchand
2019-10-10  8:27                     ` Andrew Rybchenko
2019-10-10  9:10                       ` Tiwei Bie [this message]
2019-10-01 16:29 ` [dpdk-dev] [PATCH 1/3] net/virtio: reject deferred start Rx queue setup Kevin Traynor
2019-10-01 16:39   ` Andrew Rybchenko
2019-10-09 12:32 ` [dpdk-dev] [PATCH v2 1/4] " Andrew Rybchenko
2019-10-09 12:32   ` [dpdk-dev] [PATCH v2 2/4] net/virtio: reject deferred start Tx " Andrew Rybchenko
2019-10-24  9:44     ` Maxime Coquelin
2019-10-09 12:32   ` [dpdk-dev] [PATCH v2 3/4] net/virtio: reject unsupported Rx multi queue modes Andrew Rybchenko
2019-10-24  9:44     ` Maxime Coquelin
2019-10-09 12:32   ` [dpdk-dev] [PATCH v2 4/4] net/virtio: reject unsupported Tx " Andrew Rybchenko
2019-10-24  9:44     ` Maxime Coquelin
2019-10-24  9:44   ` [dpdk-dev] [PATCH v2 1/4] net/virtio: reject deferred start Rx queue setup Maxime Coquelin
2019-10-24 10:19     ` Maxime Coquelin

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