netdev - Re: [PATCH] inet: delay address promotion check until last request in message

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Message-Id: <20151107.131714.232754521490501858.davem@davemloft.net>
Date:	Sat, 07 Nov 2015 13:17:14 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	ja@....bg
Cc:	nhorman@...driver.com, netdev@...r.kernel.org,
	kuznet@....inr.ac.ru, jmorris@...ei.org, yoshfuji@...ux-ipv6.org,
	kaber@...sh.net
Subject: Re: [PATCH] inet: delay address promotion check until last request
 in message

From: Julian Anastasov <ja@....bg>
Date: Sat, 7 Nov 2015 01:49:25 +0200 (EET)

> On Fri, 6 Nov 2015, Neil Horman wrote:
> 
>> The solution is to recognize that its pointless to promote an address to be a
>> new primary, if there is a possibility that it will just be removed in the near
>> future.  As such this patch peeks ahead to the next request in the provided
>> netlink message, and, if it is both valid and a RTM_DELADDR request, skips the
>> promotion check.  This eliminates the need to iterate through a nested for loop
> 
> 	flush can provide many parameters. As there is no
> any kind of indication in the netlink message that all addresses
> are removed, we can not avoid the promotion.
> 
>> +	 * Only check for address promotion when this is the last request
>> +	 * in this netlink transaction.  It allows this operation to complete
>> +	 * in O(n) time rather than O(n^2)
> 
> 	It is not correct to assume that one promotion per
> transaction is enough. The promotion happens in every subnet,
> it was not once per device.

Agreed, this optimization is invalid.
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