Commit d0498d9a authored Apr 16, 2008 by Pavel Emelyanov Committed by David S. Miller Apr 16, 2008

[NET]: Do not allocate unneeded memory for dev->priv alignment.



The alloc_netdev_mq() tries to produce 32-bytes alignment for both
the net_device itself and its private data. The second alignment is
achieved by adding the NETDEV_ALIGN_CONST to the whole size of
the memory to be allocated.

However, for those devices that do not need the private area, this
addition just makes the net_device weight 1024 + 32 = 1068 bytes,
i.e. consume twice as much memory.

Since loopback device is such (sizeof_priv == 0 for it), and each
net namespace creates one, this can save a noticeable amount of
memory for kernel with net namespaces turned on.

After this set the lo device is actually allocated from a size-1024
kmem cache on i386 box even with NETPOLL and WIRELESS_EXT turned on.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent f3005d7f

net/core/dev.c

+2 −1

Original line number	Original line	Diff line number	Diff line
	@@ -4000,6 +4000,7 @@ struct net_device alloc_netdev_mq(int sizeof_priv, const char name,
	alloc_size = (sizeof(*dev) + NETDEV_ALIGN_CONST +		alloc_size = (sizeof(*dev) + NETDEV_ALIGN_CONST +
	(sizeof(struct net_device_subqueue) * (queue_count - 1))) &		(sizeof(struct net_device_subqueue) * (queue_count - 1))) &
	~NETDEV_ALIGN_CONST;		~NETDEV_ALIGN_CONST;
			if (sizeof_priv)
	alloc_size += sizeof_priv + NETDEV_ALIGN_CONST;		alloc_size += sizeof_priv + NETDEV_ALIGN_CONST;

	p = kzalloc(alloc_size, GFP_KERNEL);		p = kzalloc(alloc_size, GFP_KERNEL);