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[VLAN]: Reduce memory consumed by vlan_groups 

Currently each vlan_groupd contains 8 pointers on arrays with 512
pointers on struct net_device each  :)  Such a construction "in many
cases ... wastes memory".

My proposal is to allow for some of these arrays pointers be NULL,
meaning that there are no devices in it. When a new device is added
to the vlan_group, the appropriate array is allocated.

The check in vlan_group_get_device's is safe, since the pointer
vg->vlan_devices_arrays[x] can only switch from NULL to not-NULL.
The vlan_group_prealloc_vid() is guarded with rtnl lock and is
also safe.

I've checked (I hope that) all the places, that use these arrays
and found, that the register_vlan_dev is the only place, that can
put a vlan device on an empty vlan_group.

Rough calculations shows, that after the patch a setup with a
single vlan dev (or up to 512 vlans with sequential vids) will
occupy approximately 8 times less memory.

The question I have is - does this patch makes sense, or a totally
new structures are required to store the vlan_devs?

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
This commit is contained in:
Pavel Emelyanov 2008-03-26 16:27:22 -07:00 committed by David S. Miller
parent 789e41e6f4
commit 67727184f2
2 changed files with 24 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/if_vlan.h
View File

@ -93,7 +93,7 @@ static inline struct net_device *vlan_group_get_device(struct vlan_group *vg,
{
struct net_device **array;
array = vg->vlan_devices_arrays[vlan_id / VLAN_GROUP_ARRAY_PART_LEN];
return array[vlan_id % VLAN_GROUP_ARRAY_PART_LEN];
return array ? array[vlan_id % VLAN_GROUP_ARRAY_PART_LEN] : NULL;
}
static inline void vlan_group_set_device(struct vlan_group *vg,

36
net/8021q/vlan.c
View File

@ -106,29 +106,35 @@ static void vlan_group_free(struct vlan_group *grp)
static struct vlan_group *vlan_group_alloc(int ifindex)
{
struct vlan_group *grp;
unsigned int size;
unsigned int i;
grp = kzalloc(sizeof(struct vlan_group), GFP_KERNEL);
if (!grp)
return NULL;
size = sizeof(struct net_device *) * VLAN_GROUP_ARRAY_PART_LEN;
for (i = 0; i < VLAN_GROUP_ARRAY_SPLIT_PARTS; i++) {
grp->vlan_devices_arrays[i] = kzalloc(size, GFP_KERNEL);
if (!grp->vlan_devices_arrays[i])
goto err;
}
grp->real_dev_ifindex = ifindex;
hlist_add_head_rcu(&grp->hlist,
&vlan_group_hash[vlan_grp_hashfn(ifindex)]);
return grp;
}
err:
vlan_group_free(grp);
return NULL;
static int vlan_group_prealloc_vid(struct vlan_group *vg, int vid)
{
struct net_device **array;
unsigned int size;
ASSERT_RTNL();
array = vg->vlan_devices_arrays[vid / VLAN_GROUP_ARRAY_PART_LEN];
if (array != NULL)
return 0;
size = sizeof(struct net_device *) * VLAN_GROUP_ARRAY_PART_LEN;
array = kzalloc(size, GFP_KERNEL);
if (array == NULL)
return -ENOBUFS;
vg->vlan_devices_arrays[vid / VLAN_GROUP_ARRAY_PART_LEN] = array;
return 0;
}
static void vlan_rcu_free(struct rcu_head *rcu)
@ -247,6 +253,10 @@ int register_vlan_dev(struct net_device *dev)
return -ENOBUFS;
}
err = vlan_group_prealloc_vid(grp, vlan_id);
if (err < 0)
goto out_free_group;
err = register_netdevice(dev);
if (err < 0)
goto out_free_group;