From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Sun, 29 Apr 2012 20:49:10 +0000 (-0400)
Subject: rculfhash tests: add long hash chains tests
X-Git-Tag: v0.7.0~23
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=495913bfaec0ff19107f0cc903ba1d6eade03709;p=urcu.git

rculfhash tests: add long hash chains tests

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/tests/test_urcu_hash.c b/tests/test_urcu_hash.c
index 3c7cc35..accf3c1 100644
--- a/tests/test_urcu_hash.c
+++ b/tests/test_urcu_hash.c
@@ -114,6 +114,7 @@ unsigned long init_pool_size = DEFAULT_RAND_POOL,
 	lookup_pool_size = DEFAULT_RAND_POOL,
 	write_pool_size = DEFAULT_RAND_POOL;
 int validate_lookup;
+unsigned long nr_hash_chains;	/* 0: normal table, other: number of hash chains */
 
 int count_pipe[2];
 
@@ -290,6 +291,7 @@ printf("        [not -u nor -s] Add entries (supports redundant keys).\n");
 	printf("        [-O size] Init pool size.\n");
 	printf("        [-V] Validate lookups of init values (use with filled init pool, same lookup range, with different write range).\n");
 	printf("	[-U] Uniqueness test.\n");
+	printf("	[-C] Number of hash chains.\n");
 	printf("\n\n");
 }
 
@@ -456,6 +458,9 @@ int main(int argc, char **argv)
 		case 'U':
 			test_choice = TEST_HASH_UNIQUE;
 			break;
+		case 'C':
+			nr_hash_chains = atol(argv[++i]);
+			break;
 		}
 	}
 
@@ -528,6 +533,8 @@ int main(int argc, char **argv)
 		lookup_pool_offset, lookup_pool_size);
 	printf_verbose("Update pool size offset %lu size %lu.\n",
 		write_pool_offset, write_pool_size);
+	printf_verbose("Number of hash chains: %lu.\n",
+		nr_hash_chains);
 	printf_verbose("thread %-6s, thread id : %lx, tid %lu\n",
 			"main", pthread_self(), (unsigned long)gettid());
 
diff --git a/tests/test_urcu_hash.h b/tests/test_urcu_hash.h
index a935e94..083e71c 100644
--- a/tests/test_urcu_hash.h
+++ b/tests/test_urcu_hash.h
@@ -169,6 +169,8 @@ extern unsigned long init_pool_size,
 	write_pool_size;
 extern int validate_lookup;
 
+extern unsigned long nr_hash_chains;
+
 extern int count_pipe[2];
 
 static inline void loop_sleep(unsigned long l)
@@ -323,7 +325,7 @@ void hashword2(
 
 #if (CAA_BITS_PER_LONG == 32)
 static inline
-unsigned long test_hash(const void *_key, size_t length, unsigned long seed)
+unsigned long test_hash_mix(const void *_key, size_t length, unsigned long seed)
 {
 	unsigned int key = (unsigned int) _key;
 
@@ -332,7 +334,7 @@ unsigned long test_hash(const void *_key, size_t length, unsigned long seed)
 }
 #else
 static inline
-unsigned long test_hash(const void *_key, size_t length, unsigned long seed)
+unsigned long test_hash_mix(const void *_key, size_t length, unsigned long seed)
 {
 	union {
 		uint64_t v64;
@@ -351,6 +353,29 @@ unsigned long test_hash(const void *_key, size_t length, unsigned long seed)
 }
 #endif
 
+/*
+ * Hash function with nr_hash_chains != 0 for testing purpose only!
+ * Creates very long hash chains, deteriorating the hash table into a
+ * few linked lists, depending on the nr_hash_chains value. The purpose
+ * of this test is to check how the hash table behaves with hash chains
+ * containing different values, which is a rare case in a normal hash
+ * table.
+ */
+static inline
+unsigned long test_hash(const void *_key, size_t length,
+			unsigned long seed)
+{
+	if (nr_hash_chains == 0) {
+		return test_hash_mix(_key, length, seed);
+	} else {
+		unsigned long v;
+
+		assert(length == sizeof(unsigned long));
+		v = (unsigned long) _key;
+		return v % nr_hash_chains;
+	}
+}
+
 unsigned long test_compare(const void *key1, size_t key1_len,
                            const void *key2, size_t key2_len);