perf machine: Use hashtable for machine threads

To process any events, it needs to find the thread in the machine first.
The machine maintains a rb tree to store all threads. The rb tree is
protected by a rw lock.

It is not a problem for current perf which serially processing events.
However, it will have scalability performance issue to process events in
parallel, especially on a heavy load system which have many threads.

Introduce a hashtable to divide the big rb tree into many samll rb tree
for threads. The index is thread id % hashtable size. It can reduce the
lock contention.

Committer notes:

Renamed some variables and function names to reduce semantic confusion:

  'struct threads' pointers: thread -> threads
  threads hastable index: tid -> hash_bucket
  struct threads *machine__thread() -> machine__threads()
  Cast tid to (unsigned int) to handle -1 in machine__threads() (Kan Liang)

Signed-off-by: Kan Liang <kan.liang@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Lukasz Odzioba <lukasz.odzioba@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1505096603-215017-2-git-send-email-kan.liang@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-trace.c

@@ -2730,20 +2730,23 @@ DEFINE_RESORT_RB(threads, (thread__nr_events(a->thread->priv) < thread__nr_event
 
 static size_t trace__fprintf_thread_summary(struct trace *trace, FILE *fp)
 {
-	DECLARE_RESORT_RB_MACHINE_THREADS(threads, trace->host);
 	size_t printed = trace__fprintf_threads_header(fp);
 	struct rb_node *nd;
+	int i;
 
-	if (threads == NULL) {
-		fprintf(fp, "%s", "Error sorting output by nr_events!\n");
-		return 0;
-	}
+	for (i = 0; i < THREADS__TABLE_SIZE; i++) {
+		DECLARE_RESORT_RB_MACHINE_THREADS(threads, trace->host, i);
 
-	resort_rb__for_each_entry(nd, threads)
-		printed += trace__fprintf_thread(fp, threads_entry->thread, trace);
+		if (threads == NULL) {
+			fprintf(fp, "%s", "Error sorting output by nr_events!\n");
+			return 0;
+		}
 
-	resort_rb__delete(threads);
+		resort_rb__for_each_entry(nd, threads)
+			printed += trace__fprintf_thread(fp, threads_entry->thread, trace);
 
+		resort_rb__delete(threads);
+	}
 	return printed;
 }
 

tools/perf/util/machine.c

@@ -33,18 +33,28 @@ static void dsos__init(struct dsos *dsos)
 	pthread_rwlock_init(&dsos->lock, NULL);
 }
 
+static void machine__threads_init(struct machine *machine)
+{
+	int i;
+
+	for (i = 0; i < THREADS__TABLE_SIZE; i++) {
+		struct threads *threads = &machine->threads[i];
+		threads->entries = RB_ROOT;
+		pthread_rwlock_init(&threads->lock, NULL);
+		threads->nr = 0;
+		INIT_LIST_HEAD(&threads->dead);
+		threads->last_match = NULL;
+	}
+}
+
 int machine__init(struct machine *machine, const char *root_dir, pid_t pid)
 {
 	memset(machine, 0, sizeof(*machine));
 	map_groups__init(&machine->kmaps, machine);
 	RB_CLEAR_NODE(&machine->rb_node);
 	dsos__init(&machine->dsos);
 
-	machine->threads = RB_ROOT;
-	pthread_rwlock_init(&machine->threads_lock, NULL);
-	machine->nr_threads = 0;
-	INIT_LIST_HEAD(&machine->dead_threads);
-	machine->last_match = NULL;
+	machine__threads_init(machine);
 
 	machine->vdso_info = NULL;
 	machine->env = NULL;
@@ -141,27 +151,37 @@ static void dsos__exit(struct dsos *dsos)
 void machine__delete_threads(struct machine *machine)
 {
 	struct rb_node *nd;
+	int i;
 
-	pthread_rwlock_wrlock(&machine->threads_lock);
-	nd = rb_first(&machine->threads);
-	while (nd) {
-		struct thread *t = rb_entry(nd, struct thread, rb_node);
+	for (i = 0; i < THREADS__TABLE_SIZE; i++) {
+		struct threads *threads = &machine->threads[i];
+		pthread_rwlock_wrlock(&threads->lock);
+		nd = rb_first(&threads->entries);
+		while (nd) {
+			struct thread *t = rb_entry(nd, struct thread, rb_node);
 
-		nd = rb_next(nd);
-		__machine__remove_thread(machine, t, false);
+			nd = rb_next(nd);
+			__machine__remove_thread(machine, t, false);
+		}
+		pthread_rwlock_unlock(&threads->lock);
 	}
-	pthread_rwlock_unlock(&machine->threads_lock);
 }
 
 void machine__exit(struct machine *machine)
 {
+	int i;
+
 	machine__destroy_kernel_maps(machine);
 	map_groups__exit(&machine->kmaps);
 	dsos__exit(&machine->dsos);
 	machine__exit_vdso(machine);
 	zfree(&machine->root_dir);
 	zfree(&machine->current_tid);
-	pthread_rwlock_destroy(&machine->threads_lock);
+
+	for (i = 0; i < THREADS__TABLE_SIZE; i++) {
+		struct threads *threads = &machine->threads[i];
+		pthread_rwlock_destroy(&threads->lock);
+	}
 }
 
 void machine__delete(struct machine *machine)
@@ -382,7 +402,8 @@ static struct thread *____machine__findnew_thread(struct machine *machine,
 						  pid_t pid, pid_t tid,
 						  bool create)
 {
-	struct rb_node **p = &machine->threads.rb_node;
+	struct threads *threads = machine__threads(machine, tid);
+	struct rb_node **p = &threads->entries.rb_node;
 	struct rb_node *parent = NULL;
 	struct thread *th;
 
@@ -391,22 +412,22 @@ static struct thread *____machine__findnew_thread(struct machine *machine,
 	 * so most of the time we dont have to look up
 	 * the full rbtree:
 	 */
-	th = machine->last_match;
+	th = threads->last_match;
 	if (th != NULL) {
 		if (th->tid == tid) {
 			machine__update_thread_pid(machine, th, pid);
 			return thread__get(th);
 		}
 
-		machine->last_match = NULL;
+		threads->last_match = NULL;
 	}
 
 	while (*p != NULL) {
 		parent = *p;
 		th = rb_entry(parent, struct thread, rb_node);
 
 		if (th->tid == tid) {
-			machine->last_match = th;
+			threads->last_match = th;
 			machine__update_thread_pid(machine, th, pid);
 			return thread__get(th);
 		}
@@ -423,7 +444,7 @@ static struct thread *____machine__findnew_thread(struct machine *machine,
 	th = thread__new(pid, tid);
 	if (th != NULL) {
 		rb_link_node(&th->rb_node, parent, p);
-		rb_insert_color(&th->rb_node, &machine->threads);
+		rb_insert_color(&th->rb_node, &threads->entries);
 
 		/*
 		 * We have to initialize map_groups separately
@@ -434,7 +455,7 @@ static struct thread *____machine__findnew_thread(struct machine *machine,
 		 * leader and that would screwed the rb tree.
 		 */
 		if (thread__init_map_groups(th, machine)) {
-			rb_erase_init(&th->rb_node, &machine->threads);
+			rb_erase_init(&th->rb_node, &threads->entries);
 			RB_CLEAR_NODE(&th->rb_node);
 			thread__put(th);
 			return NULL;
@@ -443,8 +464,8 @@ static struct thread *____machine__findnew_thread(struct machine *machine,
 		 * It is now in the rbtree, get a ref
 		 */
 		thread__get(th);
-		machine->last_match = th;
-		++machine->nr_threads;
+		threads->last_match = th;
+		++threads->nr;
 	}
 
 	return th;
@@ -458,21 +479,24 @@ struct thread *__machine__findnew_thread(struct machine *machine, pid_t pid, pid
 struct thread *machine__findnew_thread(struct machine *machine, pid_t pid,
 				       pid_t tid)
 {
+	struct threads *threads = machine__threads(machine, tid);
 	struct thread *th;
 
-	pthread_rwlock_wrlock(&machine->threads_lock);
+	pthread_rwlock_wrlock(&threads->lock);
 	th = __machine__findnew_thread(machine, pid, tid);
-	pthread_rwlock_unlock(&machine->threads_lock);
+	pthread_rwlock_unlock(&threads->lock);
 	return th;
 }
 
 struct thread *machine__find_thread(struct machine *machine, pid_t pid,
 				    pid_t tid)
 {
+	struct threads *threads = machine__threads(machine, tid);
 	struct thread *th;
-	pthread_rwlock_rdlock(&machine->threads_lock);
+
+	pthread_rwlock_rdlock(&threads->lock);
 	th =  ____machine__findnew_thread(machine, pid, tid, false);
-	pthread_rwlock_unlock(&machine->threads_lock);
+	pthread_rwlock_unlock(&threads->lock);
 	return th;
 }
 
@@ -719,21 +743,24 @@ size_t machine__fprintf_vmlinux_path(struct machine *machine, FILE *fp)
 
 size_t machine__fprintf(struct machine *machine, FILE *fp)
 {
-	size_t ret;
 	struct rb_node *nd;
+	size_t ret;
+	int i;
 
-	pthread_rwlock_rdlock(&machine->threads_lock);
-
-	ret = fprintf(fp, "Threads: %u\n", machine->nr_threads);
+	for (i = 0; i < THREADS__TABLE_SIZE; i++) {
+		struct threads *threads = &machine->threads[i];
+		pthread_rwlock_rdlock(&threads->lock);
 
-	for (nd = rb_first(&machine->threads); nd; nd = rb_next(nd)) {
-		struct thread *pos = rb_entry(nd, struct thread, rb_node);
+		ret = fprintf(fp, "Threads: %u\n", threads->nr);
 
-		ret += thread__fprintf(pos, fp);
-	}
+		for (nd = rb_first(&threads->entries); nd; nd = rb_next(nd)) {
+			struct thread *pos = rb_entry(nd, struct thread, rb_node);
 
-	pthread_rwlock_unlock(&machine->threads_lock);
+			ret += thread__fprintf(pos, fp);
+		}
 
+		pthread_rwlock_unlock(&threads->lock);
+	}
 	return ret;
 }
 
@@ -1479,23 +1506,25 @@ int machine__process_mmap_event(struct machine *machine, union perf_event *event
 
 static void __machine__remove_thread(struct machine *machine, struct thread *th, bool lock)
 {
-	if (machine->last_match == th)
-		machine->last_match = NULL;
+	struct threads *threads = machine__threads(machine, th->tid);
+
+	if (threads->last_match == th)
+		threads->last_match = NULL;
 
 	BUG_ON(refcount_read(&th->refcnt) == 0);
 	if (lock)
-		pthread_rwlock_wrlock(&machine->threads_lock);
-	rb_erase_init(&th->rb_node, &machine->threads);
+		pthread_rwlock_wrlock(&threads->lock);
+	rb_erase_init(&th->rb_node, &threads->entries);
 	RB_CLEAR_NODE(&th->rb_node);
-	--machine->nr_threads;
+	--threads->nr;
 	/*
 	 * Move it first to the dead_threads list, then drop the reference,
 	 * if this is the last reference, then the thread__delete destructor
 	 * will be called and we will remove it from the dead_threads list.
 	 */
-	list_add_tail(&th->node, &machine->dead_threads);
+	list_add_tail(&th->node, &threads->dead);
 	if (lock)
-		pthread_rwlock_unlock(&machine->threads_lock);
+		pthread_rwlock_unlock(&threads->lock);
 	thread__put(th);
 }
 
@@ -2140,21 +2169,26 @@ int machine__for_each_thread(struct machine *machine,
 			     int (*fn)(struct thread *thread, void *p),
 			     void *priv)
 {
+	struct threads *threads;
 	struct rb_node *nd;
 	struct thread *thread;
 	int rc = 0;
+	int i;
 
-	for (nd = rb_first(&machine->threads); nd; nd = rb_next(nd)) {
-		thread = rb_entry(nd, struct thread, rb_node);
-		rc = fn(thread, priv);
-		if (rc != 0)
-			return rc;
-	}
+	for (i = 0; i < THREADS__TABLE_SIZE; i++) {
+		threads = &machine->threads[i];
+		for (nd = rb_first(&threads->entries); nd; nd = rb_next(nd)) {
+			thread = rb_entry(nd, struct thread, rb_node);
+			rc = fn(thread, priv);
+			if (rc != 0)
+				return rc;
+		}
 
-	list_for_each_entry(thread, &machine->dead_threads, node) {
-		rc = fn(thread, priv);
-		if (rc != 0)
-			return rc;
+		list_for_each_entry(thread, &threads->dead, node) {
+			rc = fn(thread, priv);
+			if (rc != 0)
+				return rc;
+		}
 	}
 	return rc;
 }

tools/perf/util/machine.h

@@ -23,18 +23,25 @@ extern const char *ref_reloc_sym_names[];
 
 struct vdso_info;
 
+#define THREADS__TABLE_BITS	8
+#define THREADS__TABLE_SIZE	(1 << THREADS__TABLE_BITS)
+
+struct threads {
+	struct rb_root	  entries;
+	pthread_rwlock_t  lock;
+	unsigned int	  nr;
+	struct list_head  dead;
+	struct thread	  *last_match;
+};
+
 struct machine {
 	struct rb_node	  rb_node;
 	pid_t		  pid;
 	u16		  id_hdr_size;
 	bool		  comm_exec;
 	bool		  kptr_restrict_warned;
 	char		  *root_dir;
-	struct rb_root	  threads;
-	pthread_rwlock_t  threads_lock;
-	unsigned int	  nr_threads;
-	struct list_head  dead_threads;
-	struct thread	  *last_match;
+	struct threads    threads[THREADS__TABLE_SIZE];
 	struct vdso_info  *vdso_info;
 	struct perf_env   *env;
 	struct dsos	  dsos;
@@ -48,6 +55,12 @@ struct machine {
 	};
 };
 
+static inline struct threads *machine__threads(struct machine *machine, pid_t tid)
+{
+	/* Cast it to handle tid == -1 */
+	return &machine->threads[(unsigned int)tid % THREADS__TABLE_SIZE];
+}
+
 static inline
 struct map *__machine__kernel_map(struct machine *machine, enum map_type type)
 {

tools/perf/util/rb_resort.h

@@ -143,7 +143,8 @@ struct __name##_sorted *__name = __name##_sorted__new
 				  __ilist->rblist.nr_entries)
 
 /* For 'struct machine->threads' */
-#define DECLARE_RESORT_RB_MACHINE_THREADS(__name, __machine)			\
-	DECLARE_RESORT_RB(__name)(&__machine->threads, __machine->nr_threads)
+#define DECLARE_RESORT_RB_MACHINE_THREADS(__name, __machine, hash_bucket)	\
+	DECLARE_RESORT_RB(__name)(&__machine->threads[hash_bucket].entries,	\
+				  __machine->threads[hash_bucket].nr)
 
 #endif /* _PERF_RESORT_RB_H_ */