netdev - RE: [net-next rfc 1/3] net: avoid high order memory allocation for queues by using flex array

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Message-ID: <AE90C24D6B3A694183C094C60CF0A2F6026B729A@saturn3.aculab.com>
Date:	Wed, 19 Jun 2013 17:06:21 +0100
From:	"David Laight" <David.Laight@...LAB.COM>
To:	"Eric Dumazet" <eric.dumazet@...il.com>,
	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	"Jason Wang" <jasowang@...hat.com>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <hkchu@...gle.com>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: RE: [net-next rfc 1/3] net: avoid high order memory allocation for queues by using flex array

> +static void netif_free_tx_queues(struct net_device *dev)
> +{
> +	if (is_vmalloc_addr(dev->_tx))
> +		vfree(dev->_tx);
> +	else
> +		kfree(dev->_tx);
> +}
> +
>  static int netif_alloc_netdev_queues(struct net_device *dev)
>  {
>  	unsigned int count = dev->num_tx_queues;
> @@ -5261,9 +5270,11 @@ static int netif_alloc_netdev_queues(struct net_device *dev)
>  	BUG_ON(count < 1);
> 
>  	tx = kcalloc(count, sizeof(struct netdev_queue), GFP_KERNEL);
> -	if (!tx)
> -		return -ENOMEM;
> -
> +	if (!tx) {
> +		tx = vzalloc(count * sizeof(struct netdev_queue));
> +		if (!tx)
> +			return -ENOMEM;
> +	}
>  	dev->_tx = tx;

Given the number of places I've seen this code added, why
not put it in a general helper?

I also thought that malloc() with GFP_KERNEL would sleep.
Under what conditions does it fail instead?

	David