netdev - Re: [PATCH net-next] bonding: 3ad: apply ad_actor settings changes immediately

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Message-ID: <8564.1454528934@famine>
Date:	Wed, 03 Feb 2016 11:48:54 -0800
From:	Jay Vosburgh <jay.vosburgh@...onical.com>
To:	Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
cc:	Nikolay Aleksandrov <razor@...ckwall.org>, netdev@...r.kernel.org,
	davem@...emloft.net, Veaceslav Falico <vfalico@...il.com>,
	Andy Gospodarek <gospo@...ulusnetworks.com>
Subject: Re: [PATCH net-next] bonding: 3ad: apply ad_actor settings changes immediately

Nikolay Aleksandrov <nikolay@...ulusnetworks.com> wrote:

>On 02/03/2016 08:05 PM, Jay Vosburgh wrote:
>> Nikolay Aleksandrov <razor@...ckwall.org> wrote:
>> 
>>> From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
>>>
>>> Currently the bonding allows to set ad_actor_system and prio while the
>>> bond device is down, but these are actually applied only if there aren't
>>> any slaves yet (applied to bond device when first slave shows up, and to
>>> slaves at 3ad bind time). After this patch changes are applied immediately
>>> and the new values can be used/seen after the bond's upped so it's not
>>> necessary anymore to release all and enslave again to see the changes.
>>>
>>> CC: Jay Vosburgh <j.vosburgh@...il.com>
>>> CC: Veaceslav Falico <vfalico@...il.com>
>>> CC: Andy Gospodarek <gospo@...ulusnetworks.com>
>>> Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
>> 
>> 	Looks good to me.
>> 
>> Signed-off-by: Jay Vosburgh <jay.vosburgh@...onical.com>
>> 
>> 	-J
>> 
>
>Thanks Jay. Do you think it makes sense to allow setting these while the
>bond is up ? I don't see any serious problems.

	Actually, I was thinking about that when I read the patch.

	Changing these while live will trigger reselection of the
aggregator(s), since selection information in the LACPDUs will change.
It should just work itself out when the parter system sees the change.

	E.g., if bonding received a LACPDU with a changed _prio or
_system, __update_selected will clear AD_PORT_SELECTED if it doesn't
match, and that will cascade through the state machine (in
ad_mux_machine, COLLECTING_DISTRIBUTING state will revert to
MUX_ATTACHED, which will clear COLL_DIST and go from there).

	I think it may converge more quickly if bonding set ->ntt on the
ports after the change to immediately send new LACPDUs (rather than
waiting for the LACP timeout), but that's an optimization.  If the _prio
or _system are set to the same values they had previously, this is
harmless as the partner system shouldn't reselect if nothing in the
LACPDU changed.

	There's a similar optimization in bond_3ad_unbind_slave to send
a LACPDU with AGGREGATION cleared to speed up the LACP processing on the
partner system.

	-J

---
	-Jay Vosburgh, jay.vosburgh@...onical.com