On 5/8/2019 4:13 PM, Harry van Haaren wrote:
This allows plugging-in of different subtable hash-lookup-verify
routines, and allows special casing of those functions based on
known context (eg: # of bits set) of the specific subtable.
Signed-off-by: Harry van Haaren <harry.van.haa...@intel.com>
---
v9:
- Use count_1bits in favour of __builtin_popcount (Ilya)
v6:
- Implement subtable effort per packet "lookups_match" counter (Ilya)
- Remove double newline (Eelco)
- Remove doubel * before comments (Eelco)
- Reword comments in dpcls_lookup() for clarity (Harry)
---
lib/dpif-netdev.c | 135 +++++++++++++++++++++++++++++++---------------
1 file changed, 93 insertions(+), 42 deletions(-)
diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index 5a6f2abac..e2e2c14e7 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -7572,6 +7572,27 @@ dpif_dummy_register(enum dummy_level level)
/* Datapath Classifier. */
+/* forward declaration for lookup_func typedef */
Minor nit above, general rule of thumb for comment style, start with
capital letter and finish with period.
+struct dpcls_subtable;
+
+/* Lookup function for a subtable in the dpcls. This function is called
+ * by each subtable with an array of packets, and a bitmask of
packets to
+ * perform the lookup on. Using a function pointer gives flexibility to
+ * optimize the lookup function based on subtable properties and the
+ * CPU instruction set available at runtime.
+ */
+typedef uint32_t (*dpcls_subtable_lookup_func)(struct dpcls_subtable
*subtable,
+ uint32_t keys_map, const struct netdev_flow_key *keys[],
+ struct dpcls_rule **rules);
Alignment for the arguments above looks odd, typically arguments are
kept vertically in line with one another *similar to
dpcls_subtable_lookup_generic below).
+
+/* Prototype for generic lookup func, using same code path as before */
Period at end of comment above.
+uint32_t
+dpcls_subtable_lookup_generic(struct dpcls_subtable *subtable,
+ uint32_t keys_map,
+ const struct netdev_flow_key *keys[],
+ struct dpcls_rule **rules);
+
+
/* A set of rules that all have the same fields wildcarded. */
struct dpcls_subtable {
/* The fields are only used by writers. */
@@ -7581,6 +7602,13 @@ struct dpcls_subtable {
struct cmap rules; /* Contains "struct dpcls_rule"s. */
uint32_t hit_cnt; /* Number of match hits in subtable
in current
optimization interval. */
+
+ /* the lookup function to use for this subtable. If there is a known
+ * property of the subtable (eg: only 3 bits of miniflow metadata is
+ * used for the lookup) then this can point at an optimized
version of
+ * the lookup function for this particular subtable. */
the -> The above.
+ dpcls_subtable_lookup_func lookup_func;
+
struct netdev_flow_key mask; /* Wildcards for fields (const). */
/* 'mask' must be the last field, additional space is allocated
here. */
};
@@ -7640,6 +7668,10 @@ dpcls_create_subtable(struct dpcls *cls, const
struct netdev_flow_key *mask)
cmap_init(&subtable->rules);
subtable->hit_cnt = 0;
netdev_flow_key_clone(&subtable->mask, mask);
+
+ /* decide which hash/lookup/verify function to use */
+ subtable->lookup_func = dpcls_subtable_lookup_generic;
So by default dpcls_subtable_lookup_generic is set as the look up
function. Makes sense as this is the only look up available at this
stage. I assume it's later in the series a mechanism to select a
different lookup is introduced. Or by default does the lookup always
start off as the generic option when a subtable is created even when
other options are possible?
+
cmap_insert(&cls->subtables_map, &subtable->cmap_node, mask->hash);
/* Add the new subtable at the end of the pvector (with no hits
yet) */
pvector_insert(&cls->subtables, subtable, 0);
@@ -7800,6 +7832,53 @@ dpcls_rule_matches_key(const struct dpcls_rule
*rule,
return true;
}
+uint32_t
+dpcls_subtable_lookup_generic(struct dpcls_subtable *subtable,
+ uint32_t keys_map,
+ const struct netdev_flow_key *keys[],
+ struct dpcls_rule **rules)
+{
+ int i;
+ /* Compute hashes for the remaining keys. Each search-key is
+ * masked with the subtable's mask to avoid hashing the
wildcarded
+ * bits. */
+ uint32_t hashes[NETDEV_MAX_BURST];
+ ULLONG_FOR_EACH_1(i, keys_map) {
+ hashes[i] = netdev_flow_key_hash_in_mask(keys[i],
+ &subtable->mask);
+ }
+
+ /* Lookup. */
+ const struct cmap_node *nodes[NETDEV_MAX_BURST];
+ uint32_t found_map =
Minor nit. Variable declaration. You may see a mix of approaches WRT
where variables are declared. Personally I prefer at the beginning of
the function to keep with the int variable you have already declared.
looking at the original dpcls_lookup() where this code is moved from it
looks like they also declared variables at the beginning. Would be good
to follow that example.
+ cmap_find_batch(&subtable->rules, keys_map, hashes,
nodes);
+ /* Check results. When the i-th bit of found_map is set, it
means
+ * that a set of nodes with a matching hash value was found
for the
+ * i-th search-key. Due to possible hash collisions we need
to check
+ * which of the found rules, if any, really matches our masked
+ * search-key. */
+ ULLONG_FOR_EACH_1(i, found_map) {
+ struct dpcls_rule *rule;
+
+ CMAP_NODE_FOR_EACH (rule, cmap_node, nodes[i]) {
+ if (OVS_LIKELY(dpcls_rule_matches_key(rule, keys[i]))) {
+ rules[i] = rule;
+ /* Even at 20 Mpps the 32-bit hit_cnt cannot wrap
+ * within one second optimization interval. */
+ subtable->hit_cnt++;
+ goto next;
+ }
+ }
+ /* None of the found rules was a match. Reset the i-th
bit to
+ * keep searching this key in the next subtable. */
+ ULLONG_SET0(found_map, i); /* Did not match. */
+ next:
+ ; /* Keep Sparse happy. */
+ }
+
+ return found_map;
+}
+
/* For each miniflow in 'keys' performs a classifier lookup writing
the result
* into the corresponding slot in 'rules'. If a particular entry in
'keys' is
* NULL it is skipped.
@@ -7818,16 +7897,12 @@ dpcls_lookup(struct dpcls *cls, const struct
netdev_flow_key *keys[],
/* The received 'cnt' miniflows are the search-keys that will be
processed
* to find a matching entry into the available subtables.
* The number of bits in map_type is equal to NETDEV_MAX_BURST. */
- typedef uint32_t map_type;
-#define MAP_BITS (sizeof(map_type) * CHAR_BIT)
+#define MAP_BITS (sizeof(uint32_t) * CHAR_BIT)
BUILD_ASSERT_DECL(MAP_BITS >= NETDEV_MAX_BURST);
struct dpcls_subtable *subtable;
- map_type keys_map = TYPE_MAXIMUM(map_type); /* Set all bits. */
- map_type found_map;
- uint32_t hashes[MAP_BITS];
- const struct cmap_node *nodes[MAP_BITS];
+ uint32_t keys_map = TYPE_MAXIMUM(uint32_t); /* Set all bits. */
if (cnt != MAP_BITS) {
keys_map >>= MAP_BITS - cnt; /* Clear extra bits. */
@@ -7844,52 +7919,28 @@ dpcls_lookup(struct dpcls *cls, const struct
netdev_flow_key *keys[],
* search-key, the search for that key can stop because the
rules are
* non-overlapping. */
PVECTOR_FOR_EACH (subtable, &cls->subtables) {
- int i;
+ /* call the subtable specific lookup function */
+ uint32_t found_map = subtable->lookup_func(subtable, keys_map,
+ keys, rules);
- /* Compute hashes for the remaining keys. Each search-key is
- * masked with the subtable's mask to avoid hashing the
wildcarded
- * bits. */
- ULLONG_FOR_EACH_1(i, keys_map) {
- hashes[i] = netdev_flow_key_hash_in_mask(keys[i],
- &subtable->mask);
- }
- /* Lookup. */
- found_map = cmap_find_batch(&subtable->rules, keys_map,
hashes, nodes);
- /* Check results. When the i-th bit of found_map is set, it
means
- * that a set of nodes with a matching hash value was found
for the
- * i-th search-key. Due to possible hash collisions we need
to check
- * which of the found rules, if any, really matches our masked
- * search-key. */
- ULLONG_FOR_EACH_1(i, found_map) {
- struct dpcls_rule *rule;
+ /* Count the number of subtables searched for this packet
match. This
+ * estimates the "spread" of subtables looked at per matched
packet */
Minor, missing period in comment above.
+ uint32_t pkts_matched = count_1bits(found_map);
Just to clarify, at this point found_map has been returned and it only
contains matches where packets were found? i.e. it doesn't contain
matches from possible hash collisions?
+ lookups_match += pkts_matched * subtable_pos;
- CMAP_NODE_FOR_EACH (rule, cmap_node, nodes[i]) {
- if (OVS_LIKELY(dpcls_rule_matches_key(rule, keys[i]))) {
- rules[i] = rule;
- /* Even at 20 Mpps the 32-bit hit_cnt cannot wrap
- * within one second optimization interval. */
- subtable->hit_cnt++;
- lookups_match += subtable_pos;
- goto next;
- }
- }
- /* None of the found rules was a match. Reset the i-th
bit to
- * keep searching this key in the next subtable. */
- ULLONG_SET0(found_map, i); /* Did not match. */
- next:
- ; /* Keep Sparse happy. */
- }
- keys_map &= ~found_map; /* Clear the found rules. */
+ /* Clear the found rules, and return early if all packets are
found */
Missing period in comment above.
+ keys_map &= ~found_map;
if (!keys_map) {
if (num_lookups_p) {
*num_lookups_p = lookups_match;
}
- return true; /* All found. */
+ return true;
}
subtable_pos++;
}
+
if (num_lookups_p) {
*num_lookups_p = lookups_match;
}
- return false; /* Some misses. */
+ return false;
}
I've also run some performance tests on this patch but I didn't see any
notable performance degradation from the function implementation which
is good.
Ian
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