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Date: Mon, 03 Mar 2008 19:43:59 +0300
From: Pavel Emelyanov <xemul@...nvz.org>
To: Patrick McHardy <kaber@...sh.net>
CC: Linux Netdev List <netdev@...r.kernel.org>
Subject: [PATCH net-2.6.26][VLAN]: Reduce memory consumed by vlan_group-s.
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@...nvz.org>
---
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 dbc81b9..4ff856d 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;
--
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