From: Adrian Moreno <amorenoz@redhat.com>
To: Ilya Maximets <i.maximets@ovn.org>,
Aaron Conole <aconole@redhat.com>,
netdev@vger.kernel.org
Cc: dev@openvswitch.org, linux-kernel@vger.kernel.org,
Eric Dumazet <edumazet@google.com>,
linux-kselftest@vger.kernel.org, Jakub Kicinski <kuba@kernel.org>,
Paolo Abeni <pabeni@redhat.com>, Shuah Khan <shuah@kernel.org>,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [ovs-dev] [RFC net-next 1/6] openvswitch: exclude kernel flow key from upcalls
Date: Fri, 25 Nov 2022 16:29:29 +0100 [thread overview]
Message-ID: <83a0b3e4-1327-c1c4-4eb4-9a25ff533d1d@redhat.com> (raw)
In-Reply-To: <c04242ee-f125-6d95-e263-65470222d3cf@ovn.org>
On 11/23/22 22:22, Ilya Maximets wrote:
> On 11/22/22 15:03, Aaron Conole wrote:
>> When processing upcall commands, two groups of data are available to
>> userspace for processing: the actual packet data and the kernel
>> sw flow key data. The inclusion of the flow key allows the userspace
>> avoid running through the dissection again.
>>
>> However, the userspace can choose to ignore the flow key data, as is
>> the case in some ovs-vswitchd upcall processing. For these messages,
>> having the flow key data merely adds additional data to the upcall
>> pipeline without any actual gain. Userspace simply throws the data
>> away anyway.
>
> Hi, Aaron. While it's true that OVS in userpsace is re-parsing the
> packet from scratch and using the newly parsed key for the OpenFlow
> translation, the kernel-porvided key is still used in a few important
> places. Mainly for the compatibility checking. The use is described
> here in more details:
> https://docs.kernel.org/networking/openvswitch.html#flow-key-compatibility
>
> We need to compare the key generated in userspace with the key
> generated by the kernel to know if it's safe to install the new flow
> to the kernel, i.e. if the kernel and OVS userpsace are parsing the
> packet in the same way.
>
Hi Ilya,
Do we need to do that for every packet?
Could we send a bitmask of supported fields to userspace at feature negotiation
and let OVS slowpath flows that it knows the kernel won't be able to handle
properly?
> On the other hand, OVS today doesn't check the data, it only checks
> which fields are present. So, if we can generate and pass the bitmap
> of fields present in the key or something similar without sending the
> full key, that might still save some CPU cycles and memory in the
> socket buffer while preserving the ability to check for forward and
> backward compatibility. What do you think?
>
>
> The rest of the patch set seems useful even without patch #1 though.
>
> Nit: This patch #1 should probably be merged with the patch #6 and be
> at the end of a patch set, so the selftest and the main code are updated
> at the same time.
>
> Best regards, Ilya Maximets.
> _______________________________________________
> dev mailing list
> dev@openvswitch.org
> https://mail.openvswitch.org/mailman/listinfo/ovs-dev
>
Thanks
--
Adrián Moreno
next prev parent reply other threads:[~2022-11-25 15:30 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-22 14:03 [RFC net-next 0/6] Allow excluding sw flow key from upcalls Aaron Conole
2022-11-22 14:03 ` [RFC net-next 1/6] openvswitch: exclude kernel " Aaron Conole
2022-11-23 21:22 ` Ilya Maximets
2022-11-25 15:29 ` Adrian Moreno [this message]
2022-11-25 15:51 ` [ovs-dev] " Ilya Maximets
2022-11-28 9:12 ` Adrian Moreno
2022-11-29 14:26 ` Aaron Conole
2022-11-29 14:30 ` Aaron Conole
2022-11-22 14:03 ` [RFC net-next 2/6] selftests: openvswitch: add interface support Aaron Conole
2022-11-22 14:03 ` [RFC net-next 3/6] selftests: openvswitch: add flow dump support Aaron Conole
2022-11-22 14:03 ` [RFC net-next 4/6] selftests: openvswitch: adjust datapath NL message Aaron Conole
2022-11-22 14:03 ` [RFC net-next 5/6] selftests: openvswitch: add upcall support Aaron Conole
2022-11-22 14:03 ` [RFC net-next 6/6] selftests: openvswitch: add exclude support for packet commands Aaron Conole
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