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Message-Id: <1380584709-5877-1-git-send-email-baker.kernel@gmail.com>
Date: Tue, 1 Oct 2013 07:45:09 +0800
From: baker.kernel@...il.com
To: davem@...emloft.net
Cc: kuznet@....inr.ac.ru, jmorris@...ei.org, yoshfuji@...ux-ipv6.org,
kaber@...sh.net, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org,
"baker.zhang" <baker.kernel@...il.com>
Subject: [PATCH V3 net-next] fib_trie: avoid a redundant bit judgement in inflate
From: "baker.zhang" <baker.kernel@...il.com>
Because 'node' is the i'st child of 'oldnode',
thus, here 'i' equals
tkey_extract_bits(node->key, oldtnode->pos, oldtnode->bits)
we just get 1 more bit,
and need not care the detail value of this bits.
I apologize for the mistake.
I generated the patch on a branch version,
and did not notice the put_child has been changed.
I have redone the test on HEAD version with my patch.
two cases are used.
case 1. inflate a node which has a leaf child node.
case 2: inflate a node which has a an child node with skipped bits
test env:
ip link set eth0 up
ip a add dev eth0 192.168.11.1/32
here, we just focus on route table(MAIN),
so I use a "192.168.11.1/32" address to simplify the test case.
call trace:
+ fib_insert_node
+ + trie_rebalance
+ + + resize
+ + + + inflate
Test case 1: inflate a node which has a leaf child node.
===========================================================
step 1. prepare a fib trie
------------------------------------------
ip r a 192.168.0.0/24 via 192.168.11.1
ip r a 192.168.1.0/24 via 192.168.11.1
we get a fib trie.
root@...er:~# cat /proc/net/fib_trie
Main:
+-- 192.168.0.0/23 1 0 0
|-- 192.168.0.0
/24 universe UNICAST
|-- 192.168.1.0
/24 universe UNICAST
Local:
.....
step 2. Add the third route
------------------------------------------
root@...er:~# ip r a 192.168.2.0/24 via 192.168.11.1
A fib_trie leaf will be inserted in fib_insert_node before trie_rebalance.
For function 'inflate':
'inflate' is called with following trie.
+-- 192.168.0.0/22 1 1 0 <=== tn node
+-- 192.168.0.0/23 1 0 0 <== node a
|-- 192.168.0.0
/24 universe UNICAST
|-- 192.168.1.0
/24 universe UNICAST
|-- 192.168.2.0 <== leaf(node b)
When process node b, which is a leaf. here:
i is 1,
node key "192.168.2.0"
oldnode is (pos:22, bits:1)
unpatch source:
tkey_extract_bits(node->key, oldtnode->pos + oldtnode->bits, 1)
it equals:
tkey_extract_bits("192.168,2,0", 22 + 1, 1)
thus got 0, and call put_child(tn, 2*i, node); <== 2*i=2.
patched source:
tkey_extract_bits(node->key, oldtnode->pos, oldtnode->bits + 1),
tkey_extract_bits("192.168,2,0", 22, 1 + 1) <== get 2.
Test case 2: inflate a node which has a an child node with skipped bits
==========================================================================
step 1. prepare a fib trie.
ip link set eth0 up
ip a add dev eth0 192.168.11.1/32
ip r a 192.168.128.0/24 via 192.168.11.1
ip r a 192.168.0.0/24 via 192.168.11.1
ip r a 192.168.16.0/24 via 192.168.11.1
ip r a 192.168.32.0/24 via 192.168.11.1
ip r a 192.168.48.0/24 via 192.168.11.1
ip r a 192.168.144.0/24 via 192.168.11.1
ip r a 192.168.160.0/24 via 192.168.11.1
ip r a 192.168.176.0/24 via 192.168.11.1
check:
root@...er:~# cat /proc/net/fib_trie
Main:
+-- 192.168.0.0/16 1 0 0
+-- 192.168.0.0/18 2 0 0
|-- 192.168.0.0
/24 universe UNICAST
|-- 192.168.16.0
/24 universe UNICAST
|-- 192.168.32.0
/24 universe UNICAST
|-- 192.168.48.0
/24 universe UNICAST
+-- 192.168.128.0/18 2 0 0
|-- 192.168.128.0
/24 universe UNICAST
|-- 192.168.144.0
/24 universe UNICAST
|-- 192.168.160.0
/24 universe UNICAST
|-- 192.168.176.0
/24 universe UNICAST
Local:
...
step 2. add a route to trigger inflate.
ip r a 192.168.96.0/24 via 192.168.11.1
This command will call serveral times inflate.
In the first time, the fib_trie is:
________________________
+-- 192.168.128.0/(16, 1) <== tn node
+-- 192.168.0.0/(17, 1) <== node a
+-- 192.168.0.0/(18, 2)
|-- 192.168.0.0
|-- 192.168.16.0
|-- 192.168.32.0
|-- 192.168.48.0
|-- 192.168.96.0
+-- 192.168.128.0/(18, 2) <== node b.
|-- 192.168.128.0
|-- 192.168.144.0
|-- 192.168.160.0
|-- 192.168.176.0
NOTE: node b is a interal node with skipped bits.
here,
i:1,
node->key "192.168.128.0",
oldnode:(pos:16, bits:1)
so
tkey_extract_bits(node->key, oldtnode->pos + oldtnode->bits, 1)
it equals:
tkey_extract_bits("192.168,128,0", 16 + 1, 1) <=== 0
tkey_extract_bits(node->key, oldtnode->pos, oldtnode->bits, 1)
it equals:
tkey_extract_bits("192.168,128,0", 16, 1+1) <=== 2
2*i + 0 == 2, so the result is same.
Signed-off-by: baker.zhang <baker.kernel@...il.com>
---
net/ipv4/fib_trie.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 3df6d3e..45c74ba 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -762,12 +762,9 @@ static struct tnode *inflate(struct trie *t, struct tnode *tn)
if (IS_LEAF(node) || ((struct tnode *) node)->pos >
tn->pos + tn->bits - 1) {
- if (tkey_extract_bits(node->key,
- oldtnode->pos + oldtnode->bits,
- 1) == 0)
- put_child(tn, 2*i, node);
- else
- put_child(tn, 2*i+1, node);
+ put_child(tn,
+ tkey_extract_bits(node->key, oldtnode->pos, oldtnode->bits + 1),
+ node);
continue;
}
--
1.8.1.2
--
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