diff options
Diffstat (limited to 'target/linux/generic/patches-3.18/080-09-fib_trie-Update-meaning-of-pos-to-represent-unchecke.patch')
| -rw-r--r-- | target/linux/generic/patches-3.18/080-09-fib_trie-Update-meaning-of-pos-to-represent-unchecke.patch | 346 |
1 files changed, 346 insertions, 0 deletions
diff --git a/target/linux/generic/patches-3.18/080-09-fib_trie-Update-meaning-of-pos-to-represent-unchecke.patch b/target/linux/generic/patches-3.18/080-09-fib_trie-Update-meaning-of-pos-to-represent-unchecke.patch new file mode 100644 index 0000000..a0d3476 --- /dev/null +++ b/target/linux/generic/patches-3.18/080-09-fib_trie-Update-meaning-of-pos-to-represent-unchecke.patch @@ -0,0 +1,346 @@ +From: Alexander Duyck <alexander.h.duyck@redhat.com> +Date: Wed, 31 Dec 2014 10:56:12 -0800 +Subject: [PATCH] fib_trie: Update meaning of pos to represent unchecked + bits + +This change moves the pos value to the other side of the "bits" field. By +doing this it actually simplifies a significant amount of code in the trie. + +For example when halving a tree we know that the bit lost exists at +oldnode->pos, and if we inflate the tree the new bit being add is at +tn->pos. Previously to find those bits you would have to subtract pos and +bits from the keylength or start with a value of (1 << 31) and then shift +that. + +There are a number of spots throughout the code that benefit from this. In +the case of the hot-path searches the main advantage is that we can drop 2 +or more operations from the search path as we no longer need to compute the +value for the index to be shifted by and can instead just use the raw pos +value. + +In addition the tkey_extract_bits is now defunct and can be replaced by +get_index since the two operations were doing the same thing, but now +get_index does it much more quickly as it is only an xor and shift versus a +pair of shifts and a subtraction. + +Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com> +Signed-off-by: David S. Miller <davem@davemloft.net> +--- + +--- a/net/ipv4/fib_trie.c ++++ b/net/ipv4/fib_trie.c +@@ -90,8 +90,7 @@ typedef unsigned int t_key; + #define IS_TNODE(n) ((n)->bits) + #define IS_LEAF(n) (!(n)->bits) + +-#define get_shift(_kv) (KEYLENGTH - (_kv)->pos - (_kv)->bits) +-#define get_index(_key, _kv) (((_key) ^ (_kv)->key) >> get_shift(_kv)) ++#define get_index(_key, _kv) (((_key) ^ (_kv)->key) >> (_kv)->pos) + + struct tnode { + t_key key; +@@ -209,81 +208,64 @@ static inline struct tnode *tnode_get_ch + return rcu_dereference_rtnl(tn->child[i]); + } + +-static inline t_key mask_pfx(t_key k, unsigned int l) +-{ +- return (l == 0) ? 0 : k >> (KEYLENGTH-l) << (KEYLENGTH-l); +-} +- +-static inline t_key tkey_extract_bits(t_key a, unsigned int offset, unsigned int bits) +-{ +- if (offset < KEYLENGTH) +- return ((t_key)(a << offset)) >> (KEYLENGTH - bits); +- else +- return 0; +-} +- +-/* +- To understand this stuff, an understanding of keys and all their bits is +- necessary. Every node in the trie has a key associated with it, but not +- all of the bits in that key are significant. +- +- Consider a node 'n' and its parent 'tp'. +- +- If n is a leaf, every bit in its key is significant. Its presence is +- necessitated by path compression, since during a tree traversal (when +- searching for a leaf - unless we are doing an insertion) we will completely +- ignore all skipped bits we encounter. Thus we need to verify, at the end of +- a potentially successful search, that we have indeed been walking the +- correct key path. +- +- Note that we can never "miss" the correct key in the tree if present by +- following the wrong path. Path compression ensures that segments of the key +- that are the same for all keys with a given prefix are skipped, but the +- skipped part *is* identical for each node in the subtrie below the skipped +- bit! trie_insert() in this implementation takes care of that - note the +- call to tkey_sub_equals() in trie_insert(). +- +- if n is an internal node - a 'tnode' here, the various parts of its key +- have many different meanings. +- +- Example: +- _________________________________________________________________ +- | i | i | i | i | i | i | i | N | N | N | S | S | S | S | S | C | +- ----------------------------------------------------------------- +- 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 +- +- _________________________________________________________________ +- | C | C | C | u | u | u | u | u | u | u | u | u | u | u | u | u | +- ----------------------------------------------------------------- +- 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 +- +- tp->pos = 7 +- tp->bits = 3 +- n->pos = 15 +- n->bits = 4 +- +- First, let's just ignore the bits that come before the parent tp, that is +- the bits from 0 to (tp->pos-1). They are *known* but at this point we do +- not use them for anything. +- +- The bits from (tp->pos) to (tp->pos + tp->bits - 1) - "N", above - are the +- index into the parent's child array. That is, they will be used to find +- 'n' among tp's children. +- +- The bits from (tp->pos + tp->bits) to (n->pos - 1) - "S" - are skipped bits +- for the node n. +- +- All the bits we have seen so far are significant to the node n. The rest +- of the bits are really not needed or indeed known in n->key. +- +- The bits from (n->pos) to (n->pos + n->bits - 1) - "C" - are the index into +- n's child array, and will of course be different for each child. +- +- +- The rest of the bits, from (n->pos + n->bits) onward, are completely unknown +- at this point. +- +-*/ ++/* To understand this stuff, an understanding of keys and all their bits is ++ * necessary. Every node in the trie has a key associated with it, but not ++ * all of the bits in that key are significant. ++ * ++ * Consider a node 'n' and its parent 'tp'. ++ * ++ * If n is a leaf, every bit in its key is significant. Its presence is ++ * necessitated by path compression, since during a tree traversal (when ++ * searching for a leaf - unless we are doing an insertion) we will completely ++ * ignore all skipped bits we encounter. Thus we need to verify, at the end of ++ * a potentially successful search, that we have indeed been walking the ++ * correct key path. ++ * ++ * Note that we can never "miss" the correct key in the tree if present by ++ * following the wrong path. Path compression ensures that segments of the key ++ * that are the same for all keys with a given prefix are skipped, but the ++ * skipped part *is* identical for each node in the subtrie below the skipped ++ * bit! trie_insert() in this implementation takes care of that. ++ * ++ * if n is an internal node - a 'tnode' here, the various parts of its key ++ * have many different meanings. ++ * ++ * Example: ++ * _________________________________________________________________ ++ * | i | i | i | i | i | i | i | N | N | N | S | S | S | S | S | C | ++ * ----------------------------------------------------------------- ++ * 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 ++ * ++ * _________________________________________________________________ ++ * | C | C | C | u | u | u | u | u | u | u | u | u | u | u | u | u | ++ * ----------------------------------------------------------------- ++ * 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 ++ * ++ * tp->pos = 22 ++ * tp->bits = 3 ++ * n->pos = 13 ++ * n->bits = 4 ++ * ++ * First, let's just ignore the bits that come before the parent tp, that is ++ * the bits from (tp->pos + tp->bits) to 31. They are *known* but at this ++ * point we do not use them for anything. ++ * ++ * The bits from (tp->pos) to (tp->pos + tp->bits - 1) - "N", above - are the ++ * index into the parent's child array. That is, they will be used to find ++ * 'n' among tp's children. ++ * ++ * The bits from (n->pos + n->bits) to (tn->pos - 1) - "S" - are skipped bits ++ * for the node n. ++ * ++ * All the bits we have seen so far are significant to the node n. The rest ++ * of the bits are really not needed or indeed known in n->key. ++ * ++ * The bits from (n->pos) to (n->pos + n->bits - 1) - "C" - are the index into ++ * n's child array, and will of course be different for each child. ++ * ++ * The rest of the bits, from 0 to (n->pos + n->bits), are completely unknown ++ * at this point. ++ */ + + static const int halve_threshold = 25; + static const int inflate_threshold = 50; +@@ -367,7 +349,7 @@ static struct tnode *leaf_new(t_key key) + * as the nodes are searched + */ + l->key = key; +- l->pos = KEYLENGTH; ++ l->pos = 0; + /* set bits to 0 indicating we are not a tnode */ + l->bits = 0; + +@@ -400,7 +382,7 @@ static struct tnode *tnode_new(t_key key + tn->parent = NULL; + tn->pos = pos; + tn->bits = bits; +- tn->key = mask_pfx(key, pos); ++ tn->key = (shift < KEYLENGTH) ? (key >> shift) << shift : 0; + tn->full_children = 0; + tn->empty_children = 1<<bits; + } +@@ -410,14 +392,12 @@ static struct tnode *tnode_new(t_key key + return tn; + } + +-/* +- * Check whether a tnode 'n' is "full", i.e. it is an internal node ++/* Check whether a tnode 'n' is "full", i.e. it is an internal node + * and no bits are skipped. See discussion in dyntree paper p. 6 + */ +- + static inline int tnode_full(const struct tnode *tn, const struct tnode *n) + { +- return n && IS_TNODE(n) && (n->pos == (tn->pos + tn->bits)); ++ return n && ((n->pos + n->bits) == tn->pos) && IS_TNODE(n); + } + + static inline void put_child(struct tnode *tn, int i, +@@ -641,11 +621,12 @@ static struct tnode *inflate(struct trie + { + int olen = tnode_child_length(oldtnode); + struct tnode *tn; ++ t_key m; + int i; + + pr_debug("In inflate\n"); + +- tn = tnode_new(oldtnode->key, oldtnode->pos, oldtnode->bits + 1); ++ tn = tnode_new(oldtnode->key, oldtnode->pos - 1, oldtnode->bits + 1); + + if (!tn) + return ERR_PTR(-ENOMEM); +@@ -656,21 +637,18 @@ static struct tnode *inflate(struct trie + * fails. In case of failure we return the oldnode and inflate + * of tnode is ignored. + */ ++ for (i = 0, m = 1u << tn->pos; i < olen; i++) { ++ struct tnode *inode = tnode_get_child(oldtnode, i); + +- for (i = 0; i < olen; i++) { +- struct tnode *inode; +- +- inode = tnode_get_child(oldtnode, i); +- if (tnode_full(oldtnode, inode) && inode->bits > 1) { ++ if (tnode_full(oldtnode, inode) && (inode->bits > 1)) { + struct tnode *left, *right; +- t_key m = ~0U << (KEYLENGTH - 1) >> inode->pos; + +- left = tnode_new(inode->key&(~m), inode->pos + 1, ++ left = tnode_new(inode->key & ~m, inode->pos, + inode->bits - 1); + if (!left) + goto nomem; + +- right = tnode_new(inode->key|m, inode->pos + 1, ++ right = tnode_new(inode->key | m, inode->pos, + inode->bits - 1); + + if (!right) { +@@ -694,9 +672,7 @@ static struct tnode *inflate(struct trie + + /* A leaf or an internal node with skipped bits */ + if (!tnode_full(oldtnode, inode)) { +- put_child(tn, +- tkey_extract_bits(inode->key, tn->pos, tn->bits), +- inode); ++ put_child(tn, get_index(inode->key, tn), inode); + continue; + } + +@@ -767,7 +743,7 @@ static struct tnode *halve(struct trie * + + pr_debug("In halve\n"); + +- tn = tnode_new(oldtnode->key, oldtnode->pos, oldtnode->bits - 1); ++ tn = tnode_new(oldtnode->key, oldtnode->pos + 1, oldtnode->bits - 1); + + if (!tn) + return ERR_PTR(-ENOMEM); +@@ -787,7 +763,7 @@ static struct tnode *halve(struct trie * + if (left && right) { + struct tnode *newn; + +- newn = tnode_new(left->key, tn->pos + tn->bits, 1); ++ newn = tnode_new(left->key, oldtnode->pos, 1); + + if (!newn) + goto nomem; +@@ -915,7 +891,7 @@ static void trie_rebalance(struct trie * + key = tn->key; + + while (tn != NULL && (tp = node_parent(tn)) != NULL) { +- cindex = tkey_extract_bits(key, tp->pos, tp->bits); ++ cindex = get_index(key, tp); + wasfull = tnode_full(tp, tnode_get_child(tp, cindex)); + tn = resize(t, tn); + +@@ -1005,11 +981,8 @@ static struct list_head *fib_insert_node + */ + if (n) { + struct tnode *tn; +- int newpos; +- +- newpos = KEYLENGTH - __fls(n->key ^ key) - 1; + +- tn = tnode_new(key, newpos, 1); ++ tn = tnode_new(key, __fls(key ^ n->key), 1); + if (!tn) { + free_leaf_info(li); + node_free(l); +@@ -1559,12 +1532,7 @@ static int trie_flush_leaf(struct tnode + static struct tnode *leaf_walk_rcu(struct tnode *p, struct tnode *c) + { + do { +- t_key idx; +- +- if (c) +- idx = tkey_extract_bits(c->key, p->pos, p->bits) + 1; +- else +- idx = 0; ++ t_key idx = c ? idx = get_index(c->key, p) + 1 : 0; + + while (idx < 1u << p->bits) { + c = tnode_get_child_rcu(p, idx++); +@@ -1851,7 +1819,7 @@ rescan: + /* Current node exhausted, pop back up */ + p = node_parent_rcu(tn); + if (p) { +- cindex = tkey_extract_bits(tn->key, p->pos, p->bits)+1; ++ cindex = get_index(tn->key, p) + 1; + tn = p; + --iter->depth; + goto rescan; +@@ -2186,10 +2154,10 @@ static int fib_trie_seq_show(struct seq_ + if (IS_TNODE(n)) { + __be32 prf = htonl(n->key); + +- seq_indent(seq, iter->depth - 1); +- seq_printf(seq, " +-- %pI4/%d %d %d %d\n", +- &prf, n->pos, n->bits, n->full_children, +- n->empty_children); ++ seq_indent(seq, iter->depth-1); ++ seq_printf(seq, " +-- %pI4/%zu %u %u %u\n", ++ &prf, KEYLENGTH - n->pos - n->bits, n->bits, ++ n->full_children, n->empty_children); + } else { + struct leaf_info *li; + __be32 val = htonl(n->key); |