73 lines
2 KiB
Diff
73 lines
2 KiB
Diff
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From: Alexander Duyck <alexander.h.duyck@redhat.com>
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Date: Wed, 10 Dec 2014 21:49:22 -0800
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Subject: [PATCH] fib_trie: Fix trie balancing issue if new node pushes down
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existing node
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This patch addresses an issue with the level compression of the fib_trie.
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Specifically in the case of adding a new leaf that triggers a new node to
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be added that takes the place of the old node. The result is a trie where
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the 1 child tnode is on one side and one leaf is on the other which gives
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you a very deep trie. Below is the script I used to generate a trie on
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dummy0 with a 10.X.X.X family of addresses.
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ip link add type dummy
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ipval=184549374
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bit=2
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for i in `seq 1 23`
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do
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ifconfig dummy0:$bit $ipval/8
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ipval=`expr $ipval - $bit`
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bit=`expr $bit \* 2`
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done
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cat /proc/net/fib_triestat
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Running the script before the patch:
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Local:
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Aver depth: 10.82
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Max depth: 23
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Leaves: 29
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Prefixes: 30
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Internal nodes: 27
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1: 26 2: 1
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Pointers: 56
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Null ptrs: 1
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Total size: 5 kB
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After applying the patch and repeating:
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Local:
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Aver depth: 4.72
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Max depth: 9
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Leaves: 29
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Prefixes: 30
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Internal nodes: 12
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1: 3 2: 2 3: 7
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Pointers: 70
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Null ptrs: 30
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Total size: 4 kB
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What this fix does is start the rebalance at the newly created tnode
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instead of at the parent tnode. This way if there is a gap between the
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parent and the new node it doesn't prevent the new tnode from being
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coalesced with any pre-existing nodes that may have been pushed into one
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of the new nodes child branches.
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Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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--- a/net/ipv4/fib_trie.c
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+++ b/net/ipv4/fib_trie.c
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@@ -1143,8 +1143,9 @@ static struct list_head *fib_insert_node
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put_child(tp, cindex, (struct rt_trie_node *)tn);
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} else {
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rcu_assign_pointer(t->trie, (struct rt_trie_node *)tn);
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- tp = tn;
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}
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+
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+ tp = tn;
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}
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if (tp && tp->pos + tp->bits > 32)
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