[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>
diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h
index 79504b2..edd55af 100644
--- a/include/linux/if_vlan.h
+++ b/include/linux/if_vlan.h
@@ -93,7 +93,7 @@
{
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,