netdev - Re: [PATCH net-next 0/9] bonding: remove bond_next

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Date:	Sat, 28 Sep 2013 15:29:09 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	vfalico@...hat.com
Cc:	netdev@...r.kernel.org, nikolay@...hat.com,
	bhutchings@...arflare.com, fubar@...ibm.com, andy@...yhouse.net
Subject: Re: [PATCH net-next 0/9] bonding: remove bond_next_slave()

From: Veaceslav Falico <vfalico@...hat.com>
Date: Fri, 27 Sep 2013 16:11:56 +0200

> (on top of "[PATCH net-next 0/2] bonding: fix 3ad slave (de)init" - the
> patchset is essential)
> 
> Hi,
> 
> As Ben Hutchings and Nikolay Aleksandrov correctly noted -
> bond_next_slave() already is not O(1), but rather O(n), so it's only useful
> for one-off operations and shouldn't be used widely - for example, for list
> traversal, which will take O(n^2) time, which will be disastrous for any
> hot path with a large number of slaves.
> 
> Currently, bond_next_slave() is used several times in 802.3ad and for
> seq_read - bond_info_seq_next().
> 
> The 802.3ad part uses it only in constructs like:
> 
> for (X = __get_first_X(); X; X = __get_next_X()) {
> 
> where __get_next_X() uses bond_next_slave().
> 
> This for can (and should) actually be replaced by the standard
> 
> bond_for_each_slave(bond, slave, iter) {
> 	X = __get_X_by_slave(slave);
> 
> it's faster, easier to read, debug and maintain. Also, removes a lot of
> code lines.
> 
> After replacing it, the only user of bond_next_slave() is
> bond_info_seq_next() - which can, actually, implement it by itself, and not
> call another function.
> 
> So, that way, we can completely remove the bond_next_slave(), cleanup and
> optimize a bit.
> 
> p.s. the 802.3ad code is horrible, both style-wise and from the logical
> point of view - so I've decided to *not* change anything except that what
> this patch is intended to provide. The cleanup and some refactoring should
> be done in another patchset, which I've began to work on already.
> 
> Thank you!
> 
> CC: Jay Vosburgh <fubar@...ibm.com>
> CC: Andy Gospodarek <andy@...yhouse.net>
> Signed-off-by: Veaceslav Falico <vfalico@...hat.com>

Also applied, thanks.
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