Re: [PATCH v2 net-next 3/3] tuntap: reduce the size of tun_struct by using flex array.

[Pankaj Gupta <pagupta@redhat.com>]

> 
> From: Pankaj Gupta <pagupta@redhat.com>
> Date: Tue, 25 Nov 2014 00:04:04 +0530
> 
> > This patch switches to flex array to implement the flow caches, it brings
> > several advantages:
> > 
> > - Reduce the size of the tun_struct structure, which allows us to increase
> > the
> >   upper limit of queues in future.
> > - Avoid higher order memory allocation. It will be useful when switching to
> >   pure hashing in flow cache which may demand a larger size array in
> >   future.
> > 
> > After this patch, the size of tun_struct on x86_64 reduced from 8512 to
> > 328
> > 
> > Signed-off-by: Jason Wang <jasowang@redhat.com>
> > Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> > Reviewed-by: David Gibson <dgibson@redhat.com>
> 
> I see no reason to use flex arrays for this, you are preallocaing the
> memory so if anything flex array is adding an unnecessary level of
> redirection for every access in return for no real gains.
> 
> Just allocate the thing normally using kzalloc() or whatever.

I agree. Will do the changes and submit v3.
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