commit d84abbb1607bac6214754fbffd5c387fcc0ef8fb Author: Pavel Emelyanov Date: Wed Mar 26 20:36:34 2008 +0100 [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 Signed-off-by: Patrick McHardy 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 @@ 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, diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c index c35dc23..694be86 100644 --- a/net/8021q/vlan.c +++ b/net/8021q/vlan.c @@ -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;