Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/tools/perf/util/sharded_mutex.h b/tools/perf/util/sharded_mutex.h
new file mode 100644
index 0000000000..7325e969ee
--- /dev/null
+++ b/tools/perf/util/sharded_mutex.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef PERF_SHARDED_MUTEX_H
+#define PERF_SHARDED_MUTEX_H
+
+#include "mutex.h"
+#include "hashmap.h"
+
+/*
+ * In a situation where a lock is needed per object, having a mutex can be
+ * relatively memory expensive (40 bytes on x86-64). If the object can be
+ * constantly hashed, a sharded mutex is an alternative global pool of mutexes
+ * where the mutex is looked up from a hash value. This can lead to collisions
+ * if the number of shards isn't large enough.
+ */
+struct sharded_mutex {
+	/* mutexes array is 1<<cap_bits in size. */
+	unsigned int cap_bits;
+	struct mutex mutexes[];
+};
+
+struct sharded_mutex *sharded_mutex__new(size_t num_shards);
+void sharded_mutex__delete(struct sharded_mutex *sm);
+
+static inline struct mutex *sharded_mutex__get_mutex(struct sharded_mutex *sm, size_t hash)
+{
+	return &sm->mutexes[hash_bits(hash, sm->cap_bits)];
+}
+
+#endif  /* PERF_SHARDED_MUTEX_H */