netdev - Re: [PATCH] veth: use batched device unregister

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Message-ID: <BANLkTim2e1Gm_jqfY89is-FfRYTu2=G02w@mail.gmail.com>
Date:	Mon, 9 May 2011 08:56:26 +0200
From:	Michał Mirosław <mirqus@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, Alex Bligh <alex@...x.org.uk>,
	netdev@...r.kernel.org, Jesse Gross <jesse@...ira.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Ben Greear <greearb@...delatech.com>
Subject: Re: [PATCH] veth: use batched device unregister

2011/5/9 Eric Dumazet <eric.dumazet@...il.com>:
> veth devices dont use the batched device unregisters yet.
>
> Since veth are a pair of devices, it makes sense to use a batch of two
> unregisters, this roughly divide dismantle time by two.
[...]
> --- a/drivers/net/veth.c
> +++ b/drivers/net/veth.c
> @@ -451,8 +451,16 @@ static void veth_dellink(struct net_device *dev, struct list_head *head)
>        priv = netdev_priv(dev);
>        peer = priv->peer;
>
> -       unregister_netdevice_queue(dev, head);
> -       unregister_netdevice_queue(peer, head);
> +       if (head == NULL) {
> +               LIST_HEAD(list);
> +               /* make a batch of two devices to speedup unregister */
> +               unregister_netdevice_queue(dev, &list);
> +               unregister_netdevice_queue(peer, &list);
> +               unregister_netdevice_many(&list);
> +       } else {
> +               unregister_netdevice_queue(dev, head);
> +               unregister_netdevice_queue(peer, head);
> +       }

You could change dellink callers to always pass head != NULL. As a
side effect, unregister_netdevice_queue() would do just what its name
suggests.

Best Regards,
Michał Mirosław
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