netdev - Re: [RFC] netdevice ops

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Date:	Thu, 17 May 2007 21:23:16 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	Stephen Hemminger <shemminger@...ux-foundation.org>
CC:	David Miller <davem@...emloft.net>,
	Jeff Garzik <jgarzik@...ox.com>, netdev@...r.kernel.org
Subject: Re: [RFC] netdevice ops

Stephen Hemminger wrote:
> I want to take all the function pointers of 'struct net_device' and
> move them to 'struct net_device_ops'. This will save memory for the
> case of lots of devices, as well as reduce initialization code.
>
> Rough plan:
> 1. Introduce inline accessors so protocols don't dereference dev->XXX directly.
> 2. Fix protocols to use #1
> 3. Add ops field to net_device, and netdevice_register will fill in old values
>    in 'struct net_device'.
> 4...1300 Fix all network devices to use ops field
> 1301 Change accessors to use ops, get rid of old 'struct net_device' function pointers.
>
> It isn't rocket science just another code exercise. I'll patch bomb it into something
> like 2.6.23-mm first.
>
> This should really help the people who like to do 1000's of vlans etc.
>   
Vlan code uses several of the methods, so I'm not sure how it will save 
any memory unless
you will somehow have a variable sized net_device_ops structure, or 
maybe only move a
certain subset of methods into the ops struct?

Also, this will be a new chunk of memory to keep in cache and 
allocate/deallocate..wouldn't it be more efficient to
keep it local to the netdevice struct?

And there is an extra cost to dereference the point to the ops before 
calling methods?

Thanks,
Ben
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-- 
Ben Greear <greearb@...delatech.com> 
Candela Technologies Inc  http://www.candelatech.com


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