netdev - Re: Scalability of interface creation and deletion

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Message-ID: <BANLkTi=BdTaudvQJ=CVkNX1MNmH81ZFk6A@mail.gmail.com>
Date:	Mon, 9 May 2011 10:30:08 -0700
From:	Jesse Gross <jesse@...ira.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	paulmck@...ux.vnet.ibm.com, Alex Bligh <alex@...x.org.uk>,
	netdev@...r.kernel.org
Subject: Re: Scalability of interface creation and deletion

On Sun, May 8, 2011 at 2:00 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> For example, in the VLAN dismantle phase (ip link del eth0.103)
> we have 3 calls to synchronize_rcu() and one call to rcu_barrier()
>
> [ the 'extra' synchronize_rcu() call comes from unregister_vlan_dev() ]
>
> Maybe with new VLAN model, we could now remove this synchronize_net()
> call from vlan code. Jesse what do you think ?
> Once vlan_group_set_device(grp, vlan_id, NULL) had been called, why
> should we respect one rcu grace period at all, given dev is queued to
> unregister_netdevice_queue() [ which has its own couples of
> synchronize_net() / rcu_barrier() ]

Yes, I agree that the extra call to synchronize_net() provides no
value, though I think that's actually been true for a while.
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