From: Florian Fainelli <f.fainelli@gmail.com>
To: Andrew Lunn <andrew@lunn.ch>, Marek Behun <marek.behun@nic.cz>
Cc: "Ansuel Smith" <ansuelsmth@gmail.com>,
netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
"Jakub Kicinski" <kuba@kernel.org>,
"Vivien Didelot" <vivien.didelot@gmail.com>,
"Vladimir Oltean" <olteanv@gmail.com>,
"Alexei Starovoitov" <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Andrii Nakryiko" <andriin@fb.com>,
"Eric Dumazet" <edumazet@google.com>,
"Wei Wang" <weiwan@google.com>,
"Cong Wang" <cong.wang@bytedance.com>,
"Taehee Yoo" <ap420073@gmail.com>,
"Björn Töpel" <bjorn@kernel.org>,
"zhang kai" <zhangkaiheb@126.com>,
"Weilong Chen" <chenweilong@huawei.com>,
"Roopa Prabhu" <roopa@cumulusnetworks.com>,
"Di Zhu" <zhudi21@huawei.com>,
"Francis Laniel" <laniel_francis@privacyrequired.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC net-next 0/3] Multi-CPU DSA support
Date: Sun, 11 Apr 2021 19:07:08 -0700 [thread overview]
Message-ID: <d76e6ef9-8eab-2fb9-17dd-6ff4f8036337@gmail.com> (raw)
In-Reply-To: <YHNCUDJrz7ISiLVT@lunn.ch>
On 4/11/2021 11:39 AM, Andrew Lunn wrote:
> On Sun, Apr 11, 2021 at 08:01:35PM +0200, Marek Behun wrote:
>> On Sat, 10 Apr 2021 15:34:46 +0200
>> Ansuel Smith <ansuelsmth@gmail.com> wrote:
>>
>>> Hi,
>>> this is a respin of the Marek series in hope that this time we can
>>> finally make some progress with dsa supporting multi-cpu port.
>>>
>>> This implementation is similar to the Marek series but with some tweaks.
>>> This adds support for multiple-cpu port but leave the driver the
>>> decision of the type of logic to use about assigning a CPU port to the
>>> various port. The driver can also provide no preference and the CPU port
>>> is decided using a round-robin way.
>>
>> In the last couple of months I have been giving some thought to this
>> problem, and came up with one important thing: if there are multiple
>> upstream ports, it would make a lot of sense to dynamically reallocate
>> them to each user port, based on which user port is actually used, and
>> at what speed.
>>
>> For example on Turris Omnia we have 2 CPU ports and 5 user ports. All
>> ports support at most 1 Gbps. Round-robin would assign:
>> CPU port 0 - Port 0
>> CPU port 1 - Port 1
>> CPU port 0 - Port 2
>> CPU port 1 - Port 3
>> CPU port 0 - Port 4
>>
>> Now suppose that the user plugs ethernet cables only into ports 0 and 2,
>> with 1, 3 and 4 free:
>> CPU port 0 - Port 0 (plugged)
>> CPU port 1 - Port 1 (free)
>> CPU port 0 - Port 2 (plugged)
>> CPU port 1 - Port 3 (free)
>> CPU port 0 - Port 4 (free)
>>
>> We end up in a situation where ports 0 and 2 share 1 Gbps bandwidth to
>> CPU, and the second CPU port is not used at all.
>>
>> A mechanism for automatic reassignment of CPU ports would be ideal here.
>
> One thing you need to watch out for here source MAC addresses. I've
> not looked at the details, so this is more a heads up, it needs to be
> thought about.
>
> DSA slaves get there MAC address from the master interface. For a
> single CPU port, all the slaves have the same MAC address. What
> happens when you have multiple CPU ports? Does the slave interface get
> the MAC address from its CPU port?
It seems to be addressed by this part of patch 2:
+ if (ether_addr_equal(dev->dev_addr, master->dev_addr))
+ eth_hw_addr_inherit(dev, cpu_dev);
although this could create an interesting set of issues if done fully
dynamically while the data path is active.
> What happens when a slave moves
> from one CPU interface to another CPU interface? Does its MAC address
> change. ARP is going to be unhappy for a while? Also, how is the
> switch deciding on which CPU port to use? Some switches are probably
> learning the MAC address being used by the interface and doing
> forwarding based on that. So you might need unique slave MAC
> addresses, and when a slave moves, it takes it MAC address with it,
> and you hope the switch learns about the move. But considered trapped
> frames as opposed to forwarded frames. So BPDU, IGMP, etc. Generally,
> you only have the choice to send such trapped frames to one CPU
> port. So potentially, such frames are going to ingress on the wrong
> port. Does this matter? What about multicast? How do you control what
> port that ingresses on? What about RX filters on the master
> interfaces? Could it be we added it to the wrong master?
>
> For this series to make progress, we need to know what has been
> tested, and if all the more complex functionality works, not just
> basic pings.
Agreed.
--
Florian
next prev parent reply other threads:[~2021-04-12 2:07 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-10 13:34 [PATCH RFC net-next 0/3] Multi-CPU DSA support Ansuel Smith
2021-04-10 13:34 ` [PATCH RFC net-next 1/3] net: dsa: allow for multiple CPU ports Ansuel Smith
2021-04-12 3:35 ` DENG Qingfang
2021-04-12 4:41 ` Ansuel Smith
2021-04-12 15:30 ` DENG Qingfang
2021-04-12 16:17 ` Frank Wunderlich
2021-04-10 13:34 ` [PATCH RFC net-next 2/3] net: add ndo for setting the iflink property Ansuel Smith
2021-04-10 13:34 ` [PATCH RFC net-next 3/3] net: dsa: implement ndo_set_netlink for chaning port's CPU port Ansuel Smith
2021-04-10 13:34 ` [PATCH RFC iproute2-next] iplink: allow to change iplink value Ansuel Smith
2021-04-11 17:04 ` Stephen Hemminger
2021-04-11 17:09 ` Vladimir Oltean
2021-04-11 18:01 ` [PATCH RFC net-next 0/3] Multi-CPU DSA support Marek Behun
2021-04-11 18:08 ` Ansuel Smith
2021-04-11 18:39 ` Andrew Lunn
2021-04-12 2:07 ` Florian Fainelli [this message]
2021-04-12 4:53 ` Ansuel Smith
2021-04-11 18:50 ` Vladimir Oltean
2021-04-11 23:53 ` Vladimir Oltean
2021-04-12 2:10 ` Florian Fainelli
2021-04-12 5:04 ` Ansuel Smith
2021-04-12 12:46 ` Tobias Waldekranz
2021-04-12 14:35 ` Vladimir Oltean
2021-04-12 21:06 ` Tobias Waldekranz
2021-04-12 19:30 ` Marek Behun
2021-04-12 21:22 ` Tobias Waldekranz
2021-04-12 21:34 ` Vladimir Oltean
2021-04-12 21:49 ` Tobias Waldekranz
2021-04-12 21:56 ` Marek Behun
2021-04-12 22:06 ` Vladimir Oltean
2021-04-12 22:26 ` Tobias Waldekranz
2021-04-12 22:48 ` Vladimir Oltean
2021-04-12 23:04 ` Marek Behun
2021-04-12 21:50 ` Marek Behun
2021-04-12 22:05 ` Tobias Waldekranz
2021-04-12 22:55 ` Marek Behun
2021-04-12 23:09 ` Tobias Waldekranz
2021-04-12 23:13 ` Tobias Waldekranz
2021-04-12 23:54 ` Marek Behun
2021-04-13 0:27 ` Marek Behun
2021-04-13 0:31 ` Marek Behun
2021-04-13 14:46 ` Tobias Waldekranz
2021-04-13 15:14 ` Marek Behun
2021-04-13 18:16 ` Tobias Waldekranz
2021-04-14 15:14 ` Marek Behun
2021-04-14 18:39 ` Tobias Waldekranz
2021-04-14 23:39 ` Vladimir Oltean
2021-04-15 9:20 ` Tobias Waldekranz
2021-04-13 14:40 ` Tobias Waldekranz
2021-04-12 15:00 ` DENG Qingfang
2021-04-12 16:32 ` Vladimir Oltean
2021-04-12 22:04 ` Marek Behun
2021-04-12 22:17 ` Vladimir Oltean
2021-04-12 22:47 ` Marek Behun
-- strict thread matches above, loose matches on Subject: below --
2019-08-24 2:42 Marek Behún
2019-08-24 15:24 ` Andrew Lunn
2019-08-24 17:45 ` Marek Behun
2019-08-24 17:54 ` Andrew Lunn
2019-08-25 4:19 ` Marek Behun
2019-08-24 15:40 ` Vladimir Oltean
2019-08-24 15:44 ` Vladimir Oltean
2019-08-24 17:55 ` Marek Behun
2019-08-24 15:56 ` Andrew Lunn
2019-08-24 17:58 ` Marek Behun
2019-08-24 20:04 ` Florian Fainelli
2019-08-24 21:01 ` Marek Behun
2019-08-25 4:08 ` Marek Behun
2019-08-25 7:13 ` Marek Behun
2019-08-25 15:00 ` Florian Fainelli
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