From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
The lookups need to be extremely fast. Instead of doing a linear search
across all entries (which could be thousands), do a hash lookup instead.
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
include/traceeval-hist.h | 7 ++
src/histograms.c | 166 +++++++++++++++++++++++++++++++++------
2 files changed, 147 insertions(+), 26 deletions(-)
diff --git a/include/traceeval-hist.h b/include/traceeval-hist.h
index d7ffe42f3231..1edda56a712f 100644
--- a/include/traceeval-hist.h
+++ b/include/traceeval-hist.h
@@ -74,6 +74,12 @@ typedef int (*traceeval_data_cmp_fn)(struct traceeval *teval,
const struct traceeval_type *type,
const union traceeval_data *A,
const union traceeval_data *B);
+
+/* make a unique value */
+typedef int (*traceeval_data_hash_fn)(struct traceeval *teval,
+ const struct traceeval_type *type,
+ const union traceeval_data *data);
+
/*
* struct traceeval_type - Describes the type of a traceevent_data instance
* @type: The enum type that describes the traceeval_data
@@ -117,6 +123,7 @@ struct traceeval_type {
size_t id;
traceeval_data_release_fn release;
traceeval_data_cmp_fn cmp;
+ traceeval_data_hash_fn hash;
};
/* Statistics about a given entry element */
diff --git a/src/histograms.c b/src/histograms.c
index a40bfedc3cb4..54d156791193 100644
--- a/src/histograms.c
+++ b/src/histograms.c
@@ -3,6 +3,7 @@
* libtraceeval histogram interface implementation.
*
* Copyright (C) 2023 Google Inc, Stevie Alvarez <stevie.6strings@xxxxxxxxx>
+ * Copyright (C) 2023 Google Inc, Steven Rostedt <rostedt@xxxxxxxxxxx>
*/
#include <stdbool.h>
@@ -12,6 +13,14 @@
#include <traceeval-hist.h>
+#define offset_of(type, field) ((size_t)(&(((type *)(NULL))->field)))
+#define container_of(ptr, type, field) \
+ (type *)((void *)(ptr) - (void *)offset_of(type, field))
+
+#define HASH_BITS 10 /* Start with 1K of buckets */
+#define HASH_SIZE(bits) (1 << (bits))
+#define HASH_MASK(bits) (HASH_SIZE(bits) - 1)
+
/*
* Compare two integers of variable length.
*
@@ -25,23 +34,31 @@ do { \
return (a) != (b); \
} while (0) \
+
+struct hash_item {
+ struct hash_item *next;
+ unsigned key;
+};
+
+/* A hash of key-value entries */
+struct hash_table {
+ struct hash_item **hash;
+ unsigned bits;
+ size_t nr_items;
+};
+
/* A key-value pair */
struct entry {
+ struct hash_item hash;
union traceeval_data *keys;
union traceeval_data *vals;
};
-/* A table of key-value entries */
-struct hist_table {
- struct entry *map;
- size_t nr_entries;
-};
-
/* Histogram */
struct traceeval {
struct traceeval_type *key_types;
struct traceeval_type *val_types;
- struct hist_table *hist;
+ struct hash_table *hist;
size_t nr_key_types;
size_t nr_val_types;
};
@@ -299,6 +316,11 @@ struct traceeval *traceeval_init(const struct traceeval_type *keys,
err_msg = "Failed to allocate memory for histogram";
goto fail_release;
}
+ teval->hist->bits = HASH_BITS;
+ teval->hist->hash = calloc(HASH_SIZE(teval->hist->bits),
+ sizeof(*teval->hist->hash));
+ if (!teval->hist->hash)
+ goto fail_release;
return teval;
@@ -350,7 +372,7 @@ static void clean_data_set(union traceeval_data *data, struct traceeval_type *de
/*
* Free all possible data stored within the entry.
*/
-static void clean_entry(struct entry *entry, struct traceeval *teval)
+static void free_entry(struct traceeval *teval, struct entry *entry)
{
if (!entry)
return;
@@ -358,6 +380,19 @@ static void clean_entry(struct entry *entry, struct traceeval *teval)
/* free dynamic traceeval_data */
clean_data_set(entry->keys, teval->key_types, teval->nr_key_types);
clean_data_set(entry->vals, teval->val_types, teval->nr_val_types);
+
+ free(entry);
+}
+
+static void free_entries(struct traceeval *teval, struct hash_item *item)
+{
+ struct entry *entry;
+
+ while (item) {
+ entry = container_of(item, struct entry, hash);
+ item = item->next;
+ free_entry(teval, entry);
+ }
}
/*
@@ -365,16 +400,19 @@ static void clean_entry(struct entry *entry, struct traceeval *teval)
*/
static void hist_table_release(struct traceeval *teval)
{
- struct hist_table *hist = teval->hist;
+ struct hash_table *hist = teval->hist;
if (!hist)
return;
- for (size_t i = 0; i < hist->nr_entries; i++) {
- clean_entry(hist->map + i, teval);
+ for (size_t i = 0; i < HASH_SIZE(hist->bits); i++) {
+ if (!hist->hash[i])
+ continue;
+
+ free_entries(teval, hist->hash[i]);
}
- free(hist->map);
+ free(hist->hash);
free(hist);
teval->hist = NULL;
}
@@ -403,6 +441,58 @@ void traceeval_release(struct traceeval *teval)
free(teval);
}
+static unsigned long long hash_string(const char *str)
+{
+ unsigned long long key = 0;
+ int len = strlen(str);
+ int i;
+
+ for (i = 0; i < len; i++)
+ key += (unsigned long long)str[i] << ((i & 7) * 8);
+
+ return key;
+}
+
+static unsigned make_hash(struct traceeval *teval, const union traceeval_data *keys,
+ int bits)
+{
+ const struct traceeval_type *types = teval->key_types;
+ unsigned long long val;
+ unsigned key = 0;
+ int nr = teval->nr_key_types;
+
+ for (int i = 0; i < nr; i++) {
+ if (types[i].hash) {
+ key += types[i].hash(teval, &types[i], &keys[i]);
+ continue;
+ }
+
+ switch (types[i].type) {
+ case TRACEEVAL_TYPE_NUMBER_8:
+ case TRACEEVAL_TYPE_NUMBER_16:
+ case TRACEEVAL_TYPE_NUMBER_32:
+ case TRACEEVAL_TYPE_NUMBER_64:
+ case TRACEEVAL_TYPE_NUMBER:
+ val = keys[i].number_64;
+ break;
+ case TRACEEVAL_TYPE_STRING:
+ val = hash_string(keys[i].cstring);
+ break;
+ default:
+ val = 0;
+ }
+ /*
+ * This is a quick hashing function adapted from Donald E. Knuth's 32
+ * bit multiplicative hash. See The Art of Computer Programming (TAOCP).
+ * Multiplication by the Prime number, closest to the golden ratio of
+ * 2^32.
+ */
+ key += val * 2654435761;
+ }
+
+ return key & HASH_MASK(bits);
+}
+
/*
* Find the entry that @keys corresponds to within @teval.
*
@@ -411,21 +501,24 @@ void traceeval_release(struct traceeval *teval)
static int get_entry(struct traceeval *teval, const union traceeval_data *keys,
struct entry **result)
{
- struct hist_table *hist;
+ struct hash_table *hist = teval->hist;
struct entry *entry;
+ unsigned key;
int check = 0;
- int i;
if (!teval || !keys)
return -1;
+ key = make_hash(teval, keys, hist->bits);
+
hist = teval->hist;
- for (i = 0, entry = hist->map; i < hist->nr_entries; entry = &hist->map[++i]) {
+
+ for (struct hash_item *item = hist->hash[key]; item; item = item->next) {
+ entry = container_of(item, struct entry, hash);
check = compare_traceeval_data_set(teval, teval->key_types,
entry->keys, keys, teval->nr_key_types);
- if (!check)
- continue;
- break;
+ if (check)
+ break;
}
if (check > 0)
@@ -536,6 +629,7 @@ int traceeval_query(struct traceeval *teval, const union traceeval_data *keys,
/* find key and copy its corresponding value pair */
if ((check = get_entry(teval, keys, &entry)) < 1)
return check;
+
return dup_traceeval_data_set(teval->nr_val_types, teval->val_types,
entry->vals, results);
}
@@ -563,6 +657,28 @@ void traceeval_results_release(struct traceeval *teval,
data_release(teval->nr_val_types, &results, teval->val_types);
}
+static struct entry *create_hist_entry(struct traceeval *teval,
+ const union traceeval_data *keys)
+{
+ struct hash_table *hist = teval->hist;
+ struct hash_item *item;
+ unsigned key = make_hash(teval, keys, hist->bits);
+ struct entry *entry;
+
+ entry = calloc(1, sizeof(*entry));
+ if (!entry)
+ return NULL;
+
+ item = &entry->hash;
+ item->next = hist->hash[key];
+ hist->hash[key] = item;
+ item->key = key;
+
+ hist->nr_items++;
+
+ return entry;
+}
+
/*
* Create a new entry in @teval with respect to @keys and @vals.
*
@@ -574,8 +690,7 @@ static int create_entry(struct traceeval *teval,
{
union traceeval_data *new_keys;
union traceeval_data *new_vals;
- struct entry *tmp_map;
- struct hist_table *hist = teval->hist;
+ struct entry *entry;
/* copy keys */
if (dup_traceeval_data_set(teval->nr_key_types, teval->key_types,
@@ -587,13 +702,12 @@ static int create_entry(struct traceeval *teval,
vals, &new_vals) == -1)
goto fail_vals;
- /* create new entry */
- tmp_map = realloc(hist->map, ++hist->nr_entries * sizeof(*tmp_map));
- if (!tmp_map)
+ entry = create_hist_entry(teval, keys);
+ if (!entry)
goto fail;
- tmp_map->keys = new_keys;
- tmp_map->vals = new_vals;
- hist->map = tmp_map;
+
+ entry->keys = new_keys;
+ entry->vals = new_vals;
return 0;
--
2.40.1
|