[PATCH v2 0/6] Thread memory improvements and fixes

[PATCH v2 0/6] Thread memory improvements and fixes

[Ian Rogers]

The next 6 patches from:
https://lore.kernel.org/lkml/20240202061532.1939474-1-irogers@google.com/
now the initial maps fixes have landed:
https://lore.kernel.org/all/20240210031746.4057262-1-irogers@google.com/

Separate out and reimplement threads to use a hashmap for lower memory
consumption and faster look up. The fixes a regression in memory usage
where reference count checking switched to using non-invasive tree
nodes.  Reduce threads default size by 32 times and improve locking
discipline. Also, fix regressions where tids had become unordered to
make `perf report --tasks` and `perf trace --summary` output easier to
read.

v2: improve comments and a commit message.

Ian Rogers (6):
  perf report: Sort child tasks by tid
  perf trace: Ignore thread hashing in summary
  perf machine: Move fprintf to for_each loop and a callback
  perf threads: Move threads to its own files
  perf threads: Switch from rbtree to hashmap
  perf threads: Reduce table size from 256 to 8

 tools/perf/builtin-report.c           | 217 +++++++++-------
 tools/perf/builtin-trace.c            |  41 +--
 tools/perf/util/Build                 |   1 +
 tools/perf/util/bpf_lock_contention.c |   8 +-
 tools/perf/util/machine.c             | 344 +++++++-------------------
 tools/perf/util/machine.h             |  30 +--
 tools/perf/util/rb_resort.h           |   5 -
 tools/perf/util/thread.c              |   2 +-
 tools/perf/util/thread.h              |   6 -
 tools/perf/util/threads.c             | 186 ++++++++++++++
 tools/perf/util/threads.h             |  35 +++
 11 files changed, 477 insertions(+), 398 deletions(-)
 create mode 100644 tools/perf/util/threads.c
 create mode 100644 tools/perf/util/threads.h

-- 
2.44.0.rc1.240.g4c46232300-goog

[PATCH v2 1/6] perf report: Sort child tasks by tid

[Ian Rogers]

Commit 91e467bc568f ("perf machine: Use hashtable for machine
threads") made the iteration of thread tids unordered. The perf report
--tasks output now shows child threads in an order determined by the
hashing. For example, in this snippet tid 3 appears after tid 256 even
though they have the same ppid 2:

```
$ perf report --tasks
%      pid      tid     ppid  comm
         0        0       -1 |swapper
         2        2        0 | kthreadd
       256      256        2 |  kworker/12:1H-k
    693761   693761        2 |  kworker/10:1-mm
   1301762  1301762        2 |  kworker/1:1-mm_
   1302530  1302530        2 |  kworker/u32:0-k
         3        3        2 |  rcu_gp
...
```

The output is easier to read if threads appear numerically
increasing. To allow for this, read all threads into a list then sort
with a comparator that orders by the child task's of the first common
parent. The list creation and deletion are created as utilities on
machine.  The indentation is possible by counting the number of
parents a child has.

With this change the output for the same data file is now like:
```
$ perf report --tasks
%      pid      tid     ppid  comm
         0        0       -1 |swapper
         1        1        0 | systemd
       823      823        1 |  systemd-journal
       853      853        1 |  systemd-udevd
      3230     3230        1 |  systemd-timesyn
      3236     3236        1 |  auditd
      3239     3239     3236 |   audisp-syslog
      3321     3321        1 |  accounts-daemon
...
```

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/builtin-report.c | 217 +++++++++++++++++++++---------------
 tools/perf/util/machine.c   |  30 +++++
 tools/perf/util/machine.h   |  10 ++
 3 files changed, 168 insertions(+), 89 deletions(-)

diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 8e16fa261e6f..dcd93ee5fc24 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -59,6 +59,7 @@
 #include <linux/ctype.h>
 #include <signal.h>
 #include <linux/bitmap.h>
+#include <linux/list_sort.h>
 #include <linux/string.h>
 #include <linux/stringify.h>
 #include <linux/time64.h>
@@ -828,35 +829,6 @@ static void tasks_setup(struct report *rep)
 	rep->tool.no_warn = true;
 }
 
-struct task {
-	struct thread		*thread;
-	struct list_head	 list;
-	struct list_head	 children;
-};
-
-static struct task *tasks_list(struct task *task, struct machine *machine)
-{
-	struct thread *parent_thread, *thread = task->thread;
-	struct task   *parent_task;
-
-	/* Already listed. */
-	if (!list_empty(&task->list))
-		return NULL;
-
-	/* Last one in the chain. */
-	if (thread__ppid(thread) == -1)
-		return task;
-
-	parent_thread = machine__find_thread(machine, -1, thread__ppid(thread));
-	if (!parent_thread)
-		return ERR_PTR(-ENOENT);
-
-	parent_task = thread__priv(parent_thread);
-	thread__put(parent_thread);
-	list_add_tail(&task->list, &parent_task->children);
-	return tasks_list(parent_task, machine);
-}
-
 struct maps__fprintf_task_args {
 	int indent;
 	FILE *fp;
@@ -900,89 +872,156 @@ static size_t maps__fprintf_task(struct maps *maps, int indent, FILE *fp)
 	return args.printed;
 }
 
-static void task__print_level(struct task *task, FILE *fp, int level)
+static int thread_level(struct machine *machine, const struct thread *thread)
 {
-	struct thread *thread = task->thread;
-	struct task *child;
-	int comm_indent = fprintf(fp, "  %8d %8d %8d |%*s",
-				  thread__pid(thread), thread__tid(thread),
-				  thread__ppid(thread), level, "");
+	struct thread *parent_thread;
+	int res;
 
-	fprintf(fp, "%s\n", thread__comm_str(thread));
+	if (thread__tid(thread) <= 0)
+		return 0;
 
-	maps__fprintf_task(thread__maps(thread), comm_indent, fp);
+	if (thread__ppid(thread) <= 0)
+		return 1;
 
-	if (!list_empty(&task->children)) {
-		list_for_each_entry(child, &task->children, list)
-			task__print_level(child, fp, level + 1);
+	parent_thread = machine__find_thread(machine, -1, thread__ppid(thread));
+	if (!parent_thread) {
+		pr_err("Missing parent thread of %d\n", thread__tid(thread));
+		return 0;
 	}
+	res = 1 + thread_level(machine, parent_thread);
+	thread__put(parent_thread);
+	return res;
 }
 
-static int tasks_print(struct report *rep, FILE *fp)
+static void task__print_level(struct machine *machine, struct thread *thread, FILE *fp)
 {
-	struct perf_session *session = rep->session;
-	struct machine      *machine = &session->machines.host;
-	struct task *tasks, *task;
-	unsigned int nr = 0, itask = 0, i;
-	struct rb_node *nd;
-	LIST_HEAD(list);
+	int level = thread_level(machine, thread);
+	int comm_indent = fprintf(fp, "  %8d %8d %8d |%*s",
+				  thread__pid(thread), thread__tid(thread),
+				  thread__ppid(thread), level, "");
 
-	/*
-	 * No locking needed while accessing machine->threads,
-	 * because --tasks is single threaded command.
-	 */
+	fprintf(fp, "%s\n", thread__comm_str(thread));
 
-	/* Count all the threads. */
-	for (i = 0; i < THREADS__TABLE_SIZE; i++)
-		nr += machine->threads[i].nr;
+	maps__fprintf_task(thread__maps(thread), comm_indent, fp);
+}
 
-	tasks = malloc(sizeof(*tasks) * nr);
-	if (!tasks)
-		return -ENOMEM;
+/*
+ * Sort two thread list nodes such that they form a tree. The first node is the
+ * root of the tree, its children are ordered numerically after it. If a child
+ * has children itself then they appear immediately after their parent. For
+ * example, the 4 threads in the order they'd appear in the list:
+ * - init with a TID 1 and a parent of 0
+ * - systemd with a TID 3000 and a parent of init/1
+ * - systemd child thread with TID 4000, the parent is 3000
+ * - NetworkManager is a child of init with a TID of 3500.
+ */
+static int task_list_cmp(void *priv, const struct list_head *la, const struct list_head *lb)
+{
+	struct machine *machine = priv;
+	struct thread_list *task_a = list_entry(la, struct thread_list, list);
+	struct thread_list *task_b = list_entry(lb, struct thread_list, list);
+	struct thread *a = task_a->thread;
+	struct thread *b = task_b->thread;
+	int level_a, level_b, res;
+
+	/* Same thread? */
+	if (thread__tid(a) == thread__tid(b))
+		return 0;
 
-	for (i = 0; i < THREADS__TABLE_SIZE; i++) {
-		struct threads *threads = &machine->threads[i];
+	/* Compare a and b to root. */
+	if (thread__tid(a) == 0)
+		return -1;
 
-		for (nd = rb_first_cached(&threads->entries); nd;
-		     nd = rb_next(nd)) {
-			task = tasks + itask++;
+	if (thread__tid(b) == 0)
+		return 1;
 
-			task->thread = rb_entry(nd, struct thread_rb_node, rb_node)->thread;
-			INIT_LIST_HEAD(&task->children);
-			INIT_LIST_HEAD(&task->list);
-			thread__set_priv(task->thread, task);
-		}
-	}
+	/* If parents match sort by tid. */
+	if (thread__ppid(a) == thread__ppid(b))
+		return thread__tid(a) < thread__tid(b) ? -1 : 1;
 
 	/*
-	 * Iterate every task down to the unprocessed parent
-	 * and link all in task children list. Task with no
-	 * parent is added into 'list'.
+	 * Find a and b such that if they are a child of each other a and b's
+	 * tid's match, otherwise a and b have a common parent and distinct
+	 * tid's to sort by. First make the depths of the threads match.
 	 */
-	for (itask = 0; itask < nr; itask++) {
-		task = tasks + itask;
-
-		if (!list_empty(&task->list))
-			continue;
-
-		task = tasks_list(task, machine);
-		if (IS_ERR(task)) {
-			pr_err("Error: failed to process tasks\n");
-			free(tasks);
-			return PTR_ERR(task);
+	level_a = thread_level(machine, a);
+	level_b = thread_level(machine, b);
+	a = thread__get(a);
+	b = thread__get(b);
+	for (int i = level_a; i > level_b; i--) {
+		struct thread *parent = machine__find_thread(machine, -1, thread__ppid(a));
+
+		thread__put(a);
+		if (!parent) {
+			pr_err("Missing parent thread of %d\n", thread__tid(a));
+			thread__put(b);
+			return -1;
 		}
+		a = parent;
+	}
+	for (int i = level_b; i > level_a; i--) {
+		struct thread *parent = machine__find_thread(machine, -1, thread__ppid(b));
 
-		if (task)
-			list_add_tail(&task->list, &list);
+		thread__put(b);
+		if (!parent) {
+			pr_err("Missing parent thread of %d\n", thread__tid(b));
+			thread__put(a);
+			return 1;
+		}
+		b = parent;
+	}
+	/* Search up to a common parent. */
+	while (thread__ppid(a) != thread__ppid(b)) {
+		struct thread *parent;
+
+		parent = machine__find_thread(machine, -1, thread__ppid(a));
+		thread__put(a);
+		if (!parent)
+			pr_err("Missing parent thread of %d\n", thread__tid(a));
+		a = parent;
+		parent = machine__find_thread(machine, -1, thread__ppid(b));
+		thread__put(b);
+		if (!parent)
+			pr_err("Missing parent thread of %d\n", thread__tid(b));
+		b = parent;
+		if (!a || !b) {
+			/* Handle missing parent (unexpected) with some sanity. */
+			thread__put(a);
+			thread__put(b);
+			return !a && !b ? 0 : (!a ? -1 : 1);
+		}
+	}
+	if (thread__tid(a) == thread__tid(b)) {
+		/* a is a child of b or vice-versa, deeper levels appear later. */
+		res = level_a < level_b ? -1 : (level_a > level_b ? 1 : 0);
+	} else {
+		/* Sort by tid now the parent is the same. */
+		res = thread__tid(a) < thread__tid(b) ? -1 : 1;
 	}
+	thread__put(a);
+	thread__put(b);
+	return res;
+}
 
-	fprintf(fp, "# %8s %8s %8s  %s\n", "pid", "tid", "ppid", "comm");
+static int tasks_print(struct report *rep, FILE *fp)
+{
+	struct machine *machine = &rep->session->machines.host;
+	LIST_HEAD(tasks);
+	int ret;
 
-	list_for_each_entry(task, &list, list)
-		task__print_level(task, fp, 0);
+	ret = machine__thread_list(machine, &tasks);
+	if (!ret) {
+		struct thread_list *task;
 
-	free(tasks);
-	return 0;
+		list_sort(machine, &tasks, task_list_cmp);
+
+		fprintf(fp, "# %8s %8s %8s  %s\n", "pid", "tid", "ppid", "comm");
+
+		list_for_each_entry(task, &tasks, list)
+			task__print_level(machine, task->thread, fp);
+	}
+	thread_list__delete(&tasks);
+	return ret;
 }
 
 static int __cmd_report(struct report *rep)
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 3da92f18814a..7872ce92c9fc 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -3261,6 +3261,36 @@ int machines__for_each_thread(struct machines *machines,
 	return rc;
 }
 
+
+static int thread_list_cb(struct thread *thread, void *data)
+{
+	struct list_head *list = data;
+	struct thread_list *entry = malloc(sizeof(*entry));
+
+	if (!entry)
+		return -ENOMEM;
+
+	entry->thread = thread__get(thread);
+	list_add_tail(&entry->list, list);
+	return 0;
+}
+
+int machine__thread_list(struct machine *machine, struct list_head *list)
+{
+	return machine__for_each_thread(machine, thread_list_cb, list);
+}
+
+void thread_list__delete(struct list_head *list)
+{
+	struct thread_list *pos, *next;
+
+	list_for_each_entry_safe(pos, next, list, list) {
+		thread__zput(pos->thread);
+		list_del(&pos->list);
+		free(pos);
+	}
+}
+
 pid_t machine__get_current_tid(struct machine *machine, int cpu)
 {
 	if (cpu < 0 || (size_t)cpu >= machine->current_tid_sz)
diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
index 1279acda6a8a..b738ce84817b 100644
--- a/tools/perf/util/machine.h
+++ b/tools/perf/util/machine.h
@@ -280,6 +280,16 @@ int machines__for_each_thread(struct machines *machines,
 			      int (*fn)(struct thread *thread, void *p),
 			      void *priv);
 
+struct thread_list {
+	struct list_head	 list;
+	struct thread		*thread;
+};
+
+/* Make a list of struct thread_list based on threads in the machine. */
+int machine__thread_list(struct machine *machine, struct list_head *list);
+/* Free up the nodes within the thread_list list. */
+void thread_list__delete(struct list_head *list);
+
 pid_t machine__get_current_tid(struct machine *machine, int cpu);
 int machine__set_current_tid(struct machine *machine, int cpu, pid_t pid,
 			     pid_t tid);
-- 
2.44.0.rc1.240.g4c46232300-goog

[PATCH v2 2/6] perf trace: Ignore thread hashing in summary

[Ian Rogers]

Commit 91e467bc568f ("perf machine: Use hashtable for machine
threads") made the iteration of thread tids unordered. The perf trace
--summary output sorts and prints each hash bucket, rather than all
threads globally. Change this behavior by turn all threads into a
list, sort the list by number of trace events then by tids, finally
print the list. This also allows the rbtree in threads to be not
accessed outside of machine.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/builtin-trace.c  | 41 +++++++++++++++++++++----------------
 tools/perf/util/rb_resort.h |  5 -----
 2 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 109b8e64fe69..90eaff8c0f6e 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -74,6 +74,7 @@
 #include <linux/err.h>
 #include <linux/filter.h>
 #include <linux/kernel.h>
+#include <linux/list_sort.h>
 #include <linux/random.h>
 #include <linux/stringify.h>
 #include <linux/time64.h>
@@ -4312,34 +4313,38 @@ static unsigned long thread__nr_events(struct thread_trace *ttrace)
 	return ttrace ? ttrace->nr_events : 0;
 }
 
-DEFINE_RESORT_RB(threads,
-		(thread__nr_events(thread__priv(a->thread)) <
-		 thread__nr_events(thread__priv(b->thread))),
-	struct thread *thread;
-)
+static int trace_nr_events_cmp(void *priv __maybe_unused,
+			       const struct list_head *la,
+			       const struct list_head *lb)
 {
-	entry->thread = rb_entry(nd, struct thread_rb_node, rb_node)->thread;
+	struct thread_list *a = list_entry(la, struct thread_list, list);
+	struct thread_list *b = list_entry(lb, struct thread_list, list);
+	unsigned long a_nr_events = thread__nr_events(thread__priv(a->thread));
+	unsigned long b_nr_events = thread__nr_events(thread__priv(b->thread));
+
+	if (a_nr_events != b_nr_events)
+		return a_nr_events < b_nr_events ? -1 : 1;
+
+	/* Identical number of threads, place smaller tids first. */
+	return thread__tid(a->thread) < thread__tid(b->thread)
+		? -1
+		: (thread__tid(a->thread) > thread__tid(b->thread) ? 1 : 0);
 }
 
 static size_t trace__fprintf_thread_summary(struct trace *trace, FILE *fp)
 {
 	size_t printed = trace__fprintf_threads_header(fp);
-	struct rb_node *nd;
-	int i;
-
-	for (i = 0; i < THREADS__TABLE_SIZE; i++) {
-		DECLARE_RESORT_RB_MACHINE_THREADS(threads, trace->host, i);
+	LIST_HEAD(threads);
 
-		if (threads == NULL) {
-			fprintf(fp, "%s", "Error sorting output by nr_events!\n");
-			return 0;
-		}
+	if (machine__thread_list(trace->host, &threads) == 0) {
+		struct thread_list *pos;
 
-		resort_rb__for_each_entry(nd, threads)
-			printed += trace__fprintf_thread(fp, threads_entry->thread, trace);
+		list_sort(NULL, &threads, trace_nr_events_cmp);
 
-		resort_rb__delete(threads);
+		list_for_each_entry(pos, &threads, list)
+			printed += trace__fprintf_thread(fp, pos->thread, trace);
 	}
+	thread_list__delete(&threads);
 	return printed;
 }
 
diff --git a/tools/perf/util/rb_resort.h b/tools/perf/util/rb_resort.h
index 376e86cb4c3c..d927a0d25052 100644
--- a/tools/perf/util/rb_resort.h
+++ b/tools/perf/util/rb_resort.h
@@ -143,9 +143,4 @@ struct __name##_sorted *__name = __name##_sorted__new
 	DECLARE_RESORT_RB(__name)(&__ilist->rblist.entries.rb_root,		\
 				  __ilist->rblist.nr_entries)
 
-/* For 'struct machine->threads' */
-#define DECLARE_RESORT_RB_MACHINE_THREADS(__name, __machine, hash_bucket)    \
- DECLARE_RESORT_RB(__name)(&__machine->threads[hash_bucket].entries.rb_root, \
-			   __machine->threads[hash_bucket].nr)
-
 #endif /* _PERF_RESORT_RB_H_ */
-- 
2.44.0.rc1.240.g4c46232300-goog

[PATCH v2 3/6] perf machine: Move fprintf to for_each loop and a callback

[Ian Rogers]

Avoid exposing the threads data structure by switching to the callback
machine__for_each_thread approach. machine__fprintf is only used in
tests and verbose >3 output so don't turn to list and sort. Add
machine__threads_nr to be refactored later.

Note, all existing *_fprintf routines ignore fprintf errors.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/machine.c | 43 ++++++++++++++++++++++++---------------
 1 file changed, 27 insertions(+), 16 deletions(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 7872ce92c9fc..e072b2115b64 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1113,29 +1113,40 @@ size_t machine__fprintf_vmlinux_path(struct machine *machine, FILE *fp)
 	return printed;
 }
 
-size_t machine__fprintf(struct machine *machine, FILE *fp)
+struct machine_fprintf_cb_args {
+	FILE *fp;
+	size_t printed;
+};
+
+static int machine_fprintf_cb(struct thread *thread, void *data)
 {
-	struct rb_node *nd;
-	size_t ret;
-	int i;
+	struct machine_fprintf_cb_args *args = data;
 
-	for (i = 0; i < THREADS__TABLE_SIZE; i++) {
-		struct threads *threads = &machine->threads[i];
+	/* TODO: handle fprintf errors. */
+	args->printed += thread__fprintf(thread, args->fp);
+	return 0;
+}
 
-		down_read(&threads->lock);
+static size_t machine__threads_nr(const struct machine *machine)
+{
+	size_t nr = 0;
 
-		ret = fprintf(fp, "Threads: %u\n", threads->nr);
+	for (int i = 0; i < THREADS__TABLE_SIZE; i++)
+		nr += machine->threads[i].nr;
 
-		for (nd = rb_first_cached(&threads->entries); nd;
-		     nd = rb_next(nd)) {
-			struct thread *pos = rb_entry(nd, struct thread_rb_node, rb_node)->thread;
+	return nr;
+}
 
-			ret += thread__fprintf(pos, fp);
-		}
+size_t machine__fprintf(struct machine *machine, FILE *fp)
+{
+	struct machine_fprintf_cb_args args = {
+		.fp = fp,
+		.printed = 0,
+	};
+	size_t ret = fprintf(fp, "Threads: %zu\n", machine__threads_nr(machine));
 
-		up_read(&threads->lock);
-	}
-	return ret;
+	machine__for_each_thread(machine, machine_fprintf_cb, &args);
+	return ret + args.printed;
 }
 
 static struct dso *machine__get_kernel(struct machine *machine)
-- 
2.44.0.rc1.240.g4c46232300-goog

[PATCH v2 4/6] perf threads: Move threads to its own files

[Ian Rogers]

Move threads out of machine and move thread_rb_node into the C
file. This hides the implementation of threads from the rest of the
code allowing for it to be refactored. Note, the implementation here
is removed in the next patch in the series which moves to a hashtable.

Locking discipline is tightened up in this change. When a function is
added to threads.c care is taken that the threads lock is held
appropriately. This replaces somewhat adhoc use of the lock in
machine, and adds the lock in places it was missed primarily
threads__nr. In the previous code it was the caller's responsibility
to hold the right lock before calling an internal "__" version of the
function.

As the lock is now encapsulated in threads, the findnew function
requires holding it (as it already did in machine). Rather than do
conditionals with locks based on whether the thread should be created
(which could potentially be error prone with a read lock match with a
write unlock), have a separate threads__find that won't create the
thread and only holds the read lock. This effectively duplicates the
findnew logic, with the existing findnew logic only operating under a
write lock assuming creation is necessary as a previous find
failed. The creation may still fail with the write lock due to another
thread. The duplication is removed in the next patch that delegates
the implementation to hashtable.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/Build                 |   1 +
 tools/perf/util/bpf_lock_contention.c |   8 +-
 tools/perf/util/machine.c             | 287 ++++----------------------
 tools/perf/util/machine.h             |  20 +-
 tools/perf/util/thread.c              |   2 +-
 tools/perf/util/thread.h              |   6 -
 tools/perf/util/threads.c             | 244 ++++++++++++++++++++++
 tools/perf/util/threads.h             |  35 ++++
 8 files changed, 325 insertions(+), 278 deletions(-)
 create mode 100644 tools/perf/util/threads.c
 create mode 100644 tools/perf/util/threads.h

diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index 2cbeeb79b6ef..e0a723e24503 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -72,6 +72,7 @@ perf-y += ordered-events.o
 perf-y += namespaces.o
 perf-y += comm.o
 perf-y += thread.o
+perf-y += threads.o
 perf-y += thread_map.o
 perf-y += parse-events-flex.o
 perf-y += parse-events-bison.o
diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c
index 31ff19afc20c..3992c8a9fd96 100644
--- a/tools/perf/util/bpf_lock_contention.c
+++ b/tools/perf/util/bpf_lock_contention.c
@@ -210,7 +210,7 @@ static const char *lock_contention_get_name(struct lock_contention *con,
 
 		/* do not update idle comm which contains CPU number */
 		if (pid) {
-			struct thread *t = __machine__findnew_thread(machine, /*pid=*/-1, pid);
+			struct thread *t = machine__findnew_thread(machine, /*pid=*/-1, pid);
 
 			if (t == NULL)
 				return name;
@@ -302,9 +302,9 @@ int lock_contention_read(struct lock_contention *con)
 		return -1;
 
 	if (con->aggr_mode == LOCK_AGGR_TASK) {
-		struct thread *idle = __machine__findnew_thread(machine,
-								/*pid=*/0,
-								/*tid=*/0);
+		struct thread *idle = machine__findnew_thread(machine,
+							      /*pid=*/0,
+							      /*tid=*/0);
 		thread__set_comm(idle, "swapper", /*timestamp=*/0);
 	}
 
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index e072b2115b64..e668a97255f8 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -43,9 +43,6 @@
 #include <linux/string.h>
 #include <linux/zalloc.h>
 
-static void __machine__remove_thread(struct machine *machine, struct thread_rb_node *nd,
-				     struct thread *th, bool lock);
-
 static struct dso *machine__kernel_dso(struct machine *machine)
 {
 	return map__dso(machine->vmlinux_map);
@@ -58,35 +55,6 @@ static void dsos__init(struct dsos *dsos)
 	init_rwsem(&dsos->lock);
 }
 
-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_CACHED;
-		init_rwsem(&threads->lock);
-		threads->nr = 0;
-		threads->last_match = NULL;
-	}
-}
-
-static int thread_rb_node__cmp_tid(const void *key, const struct rb_node *nd)
-{
-	int to_find = (int) *((pid_t *)key);
-
-	return to_find - (int)thread__tid(rb_entry(nd, struct thread_rb_node, rb_node)->thread);
-}
-
-static struct thread_rb_node *thread_rb_node__find(const struct thread *th,
-						   struct rb_root *tree)
-{
-	pid_t to_find = thread__tid(th);
-	struct rb_node *nd = rb_find(&to_find, tree, thread_rb_node__cmp_tid);
-
-	return rb_entry(nd, struct thread_rb_node, rb_node);
-}
-
 static int machine__set_mmap_name(struct machine *machine)
 {
 	if (machine__is_host(machine))
@@ -120,7 +88,7 @@ int machine__init(struct machine *machine, const char *root_dir, pid_t pid)
 	RB_CLEAR_NODE(&machine->rb_node);
 	dsos__init(&machine->dsos);
 
-	machine__threads_init(machine);
+	threads__init(&machine->threads);
 
 	machine->vdso_info = NULL;
 	machine->env = NULL;
@@ -221,27 +189,11 @@ static void dsos__exit(struct dsos *dsos)
 
 void machine__delete_threads(struct machine *machine)
 {
-	struct rb_node *nd;
-	int i;
-
-	for (i = 0; i < THREADS__TABLE_SIZE; i++) {
-		struct threads *threads = &machine->threads[i];
-		down_write(&threads->lock);
-		nd = rb_first_cached(&threads->entries);
-		while (nd) {
-			struct thread_rb_node *trb = rb_entry(nd, struct thread_rb_node, rb_node);
-
-			nd = rb_next(nd);
-			__machine__remove_thread(machine, trb, trb->thread, false);
-		}
-		up_write(&threads->lock);
-	}
+	threads__remove_all_threads(&machine->threads);
 }
 
 void machine__exit(struct machine *machine)
 {
-	int i;
-
 	if (machine == NULL)
 		return;
 
@@ -254,12 +206,7 @@ void machine__exit(struct machine *machine)
 	zfree(&machine->current_tid);
 	zfree(&machine->kallsyms_filename);
 
-	machine__delete_threads(machine);
-	for (i = 0; i < THREADS__TABLE_SIZE; i++) {
-		struct threads *threads = &machine->threads[i];
-
-		exit_rwsem(&threads->lock);
-	}
+	threads__exit(&machine->threads);
 }
 
 void machine__delete(struct machine *machine)
@@ -526,7 +473,7 @@ static void machine__update_thread_pid(struct machine *machine,
 	if (thread__pid(th) == thread__tid(th))
 		return;
 
-	leader = __machine__findnew_thread(machine, thread__pid(th), thread__pid(th));
+	leader = machine__findnew_thread(machine, thread__pid(th), thread__pid(th));
 	if (!leader)
 		goto out_err;
 
@@ -560,160 +507,55 @@ static void machine__update_thread_pid(struct machine *machine,
 	goto out_put;
 }
 
-/*
- * Front-end cache - TID lookups come in blocks,
- * so most of the time we dont have to look up
- * the full rbtree:
- */
-static struct thread*
-__threads__get_last_match(struct threads *threads, struct machine *machine,
-			  int pid, int tid)
-{
-	struct thread *th;
-
-	th = threads->last_match;
-	if (th != NULL) {
-		if (thread__tid(th) == tid) {
-			machine__update_thread_pid(machine, th, pid);
-			return thread__get(th);
-		}
-		thread__put(threads->last_match);
-		threads->last_match = NULL;
-	}
-
-	return NULL;
-}
-
-static struct thread*
-threads__get_last_match(struct threads *threads, struct machine *machine,
-			int pid, int tid)
-{
-	struct thread *th = NULL;
-
-	if (perf_singlethreaded)
-		th = __threads__get_last_match(threads, machine, pid, tid);
-
-	return th;
-}
-
-static void
-__threads__set_last_match(struct threads *threads, struct thread *th)
-{
-	thread__put(threads->last_match);
-	threads->last_match = thread__get(th);
-}
-
-static void
-threads__set_last_match(struct threads *threads, struct thread *th)
-{
-	if (perf_singlethreaded)
-		__threads__set_last_match(threads, th);
-}
-
 /*
  * Caller must eventually drop thread->refcnt returned with a successful
  * lookup/new thread inserted.
  */
-static struct thread *____machine__findnew_thread(struct machine *machine,
-						  struct threads *threads,
-						  pid_t pid, pid_t tid,
-						  bool create)
+static struct thread *__machine__findnew_thread(struct machine *machine,
+						pid_t pid,
+						pid_t tid,
+						bool create)
 {
-	struct rb_node **p = &threads->entries.rb_root.rb_node;
-	struct rb_node *parent = NULL;
-	struct thread *th;
-	struct thread_rb_node *nd;
-	bool leftmost = true;
+	struct thread *th = threads__find(&machine->threads, tid);
+	bool created;
 
-	th = threads__get_last_match(threads, machine, pid, tid);
-	if (th)
+	if (th) {
+		machine__update_thread_pid(machine, th, pid);
 		return th;
-
-	while (*p != NULL) {
-		parent = *p;
-		th = rb_entry(parent, struct thread_rb_node, rb_node)->thread;
-
-		if (thread__tid(th) == tid) {
-			threads__set_last_match(threads, th);
-			machine__update_thread_pid(machine, th, pid);
-			return thread__get(th);
-		}
-
-		if (tid < thread__tid(th))
-			p = &(*p)->rb_left;
-		else {
-			p = &(*p)->rb_right;
-			leftmost = false;
-		}
 	}
-
 	if (!create)
 		return NULL;
 
-	th = thread__new(pid, tid);
-	if (th == NULL)
-		return NULL;
-
-	nd = malloc(sizeof(*nd));
-	if (nd == NULL) {
-		thread__put(th);
-		return NULL;
-	}
-	nd->thread = th;
-
-	rb_link_node(&nd->rb_node, parent, p);
-	rb_insert_color_cached(&nd->rb_node, &threads->entries, leftmost);
-	/*
-	 * We have to initialize maps separately after rb tree is updated.
-	 *
-	 * The reason is that we call machine__findnew_thread within
-	 * thread__init_maps to find the thread leader and that would screwed
-	 * the rb tree.
-	 */
-	if (thread__init_maps(th, machine)) {
-		pr_err("Thread init failed thread %d\n", pid);
-		rb_erase_cached(&nd->rb_node, &threads->entries);
-		RB_CLEAR_NODE(&nd->rb_node);
-		free(nd);
-		thread__put(th);
-		return NULL;
-	}
-	/*
-	 * It is now in the rbtree, get a ref
-	 */
-	threads__set_last_match(threads, th);
-	++threads->nr;
-
-	return thread__get(th);
-}
+	th = threads__findnew(&machine->threads, pid, tid, &created);
+	if (created) {
+		/*
+		 * We have to initialize maps separately after rb tree is
+		 * updated.
+		 *
+		 * The reason is that we call machine__findnew_thread within
+		 * thread__init_maps to find the thread leader and that would
+		 * screwed the rb tree.
+		 */
+		if (thread__init_maps(th, machine)) {
+			pr_err("Thread init failed thread %d\n", pid);
+			threads__remove(&machine->threads, th);
+			thread__put(th);
+			return NULL;
+		}
+	} else
+		machine__update_thread_pid(machine, th, pid);
 
-struct thread *__machine__findnew_thread(struct machine *machine, pid_t pid, pid_t tid)
-{
-	return ____machine__findnew_thread(machine, machine__threads(machine, tid), pid, tid, true);
+	return th;
 }
 
-struct thread *machine__findnew_thread(struct machine *machine, pid_t pid,
-				       pid_t tid)
+struct thread *machine__findnew_thread(struct machine *machine, pid_t pid, pid_t tid)
 {
-	struct threads *threads = machine__threads(machine, tid);
-	struct thread *th;
-
-	down_write(&threads->lock);
-	th = __machine__findnew_thread(machine, pid, tid);
-	up_write(&threads->lock);
-	return th;
+	return __machine__findnew_thread(machine, pid, tid, /*create=*/true);
 }
 
-struct thread *machine__find_thread(struct machine *machine, pid_t pid,
-				    pid_t tid)
+struct thread *machine__find_thread(struct machine *machine, pid_t pid, pid_t tid)
 {
-	struct threads *threads = machine__threads(machine, tid);
-	struct thread *th;
-
-	down_read(&threads->lock);
-	th =  ____machine__findnew_thread(machine, threads, pid, tid, false);
-	up_read(&threads->lock);
-	return th;
+	return __machine__findnew_thread(machine, pid, tid, /*create=*/false);
 }
 
 /*
@@ -1127,23 +969,13 @@ static int machine_fprintf_cb(struct thread *thread, void *data)
 	return 0;
 }
 
-static size_t machine__threads_nr(const struct machine *machine)
-{
-	size_t nr = 0;
-
-	for (int i = 0; i < THREADS__TABLE_SIZE; i++)
-		nr += machine->threads[i].nr;
-
-	return nr;
-}
-
 size_t machine__fprintf(struct machine *machine, FILE *fp)
 {
 	struct machine_fprintf_cb_args args = {
 		.fp = fp,
 		.printed = 0,
 	};
-	size_t ret = fprintf(fp, "Threads: %zu\n", machine__threads_nr(machine));
+	size_t ret = fprintf(fp, "Threads: %zu\n", threads__nr(&machine->threads));
 
 	machine__for_each_thread(machine, machine_fprintf_cb, &args);
 	return ret + args.printed;
@@ -2069,36 +1901,9 @@ int machine__process_mmap_event(struct machine *machine, union perf_event *event
 	return 0;
 }
 
-static void __machine__remove_thread(struct machine *machine, struct thread_rb_node *nd,
-				     struct thread *th, bool lock)
-{
-	struct threads *threads = machine__threads(machine, thread__tid(th));
-
-	if (!nd)
-		nd = thread_rb_node__find(th, &threads->entries.rb_root);
-
-	if (threads->last_match && RC_CHK_EQUAL(threads->last_match, th))
-		threads__set_last_match(threads, NULL);
-
-	if (lock)
-		down_write(&threads->lock);
-
-	BUG_ON(refcount_read(thread__refcnt(th)) == 0);
-
-	thread__put(nd->thread);
-	rb_erase_cached(&nd->rb_node, &threads->entries);
-	RB_CLEAR_NODE(&nd->rb_node);
-	--threads->nr;
-
-	free(nd);
-
-	if (lock)
-		up_write(&threads->lock);
-}
-
 void machine__remove_thread(struct machine *machine, struct thread *th)
 {
-	return __machine__remove_thread(machine, NULL, th, true);
+	return threads__remove(&machine->threads, th);
 }
 
 int machine__process_fork_event(struct machine *machine, union perf_event *event,
@@ -3232,23 +3037,7 @@ int machine__for_each_thread(struct machine *machine,
 			     int (*fn)(struct thread *thread, void *p),
 			     void *priv)
 {
-	struct threads *threads;
-	struct rb_node *nd;
-	int rc = 0;
-	int i;
-
-	for (i = 0; i < THREADS__TABLE_SIZE; i++) {
-		threads = &machine->threads[i];
-		for (nd = rb_first_cached(&threads->entries); nd;
-		     nd = rb_next(nd)) {
-			struct thread_rb_node *trb = rb_entry(nd, struct thread_rb_node, rb_node);
-
-			rc = fn(trb->thread, priv);
-			if (rc != 0)
-				return rc;
-		}
-	}
-	return rc;
+	return threads__for_each_thread(&machine->threads, fn, priv);
 }
 
 int machines__for_each_thread(struct machines *machines,
diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
index b738ce84817b..e28c787616fe 100644
--- a/tools/perf/util/machine.h
+++ b/tools/perf/util/machine.h
@@ -7,6 +7,7 @@
 #include "maps.h"
 #include "dsos.h"
 #include "rwsem.h"
+#include "threads.h"
 
 struct addr_location;
 struct branch_stack;
@@ -28,16 +29,6 @@ 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_cached  entries;
-	struct rw_semaphore    lock;
-	unsigned int	       nr;
-	struct thread	       *last_match;
-};
-
 struct machine {
 	struct rb_node	  rb_node;
 	pid_t		  pid;
@@ -48,7 +39,7 @@ struct machine {
 	char		  *root_dir;
 	char		  *mmap_name;
 	char		  *kallsyms_filename;
-	struct threads    threads[THREADS__TABLE_SIZE];
+	struct threads    threads;
 	struct vdso_info  *vdso_info;
 	struct perf_env   *env;
 	struct dsos	  dsos;
@@ -69,12 +60,6 @@ struct machine {
 	bool		  trampolines_mapped;
 };
 
-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];
-}
-
 /*
  * The main kernel (vmlinux) map
  */
@@ -220,7 +205,6 @@ bool machine__is(struct machine *machine, const char *arch);
 bool machine__normalized_is(struct machine *machine, const char *arch);
 int machine__nr_cpus_avail(struct machine *machine);
 
-struct thread *__machine__findnew_thread(struct machine *machine, pid_t pid, pid_t tid);
 struct thread *machine__findnew_thread(struct machine *machine, pid_t pid, pid_t tid);
 
 struct dso *machine__findnew_dso_id(struct machine *machine, const char *filename, struct dso_id *id);
diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index c59ab4d79163..1aa8962dcf52 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -26,7 +26,7 @@ int thread__init_maps(struct thread *thread, struct machine *machine)
 	if (pid == thread__tid(thread) || pid == -1) {
 		thread__set_maps(thread, maps__new(machine));
 	} else {
-		struct thread *leader = __machine__findnew_thread(machine, pid, pid);
+		struct thread *leader = machine__findnew_thread(machine, pid, pid);
 
 		if (leader) {
 			thread__set_maps(thread, maps__get(thread__maps(leader)));
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index df344262eaee..8b4a3c69bad1 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -3,7 +3,6 @@
 #define __PERF_THREAD_H
 
 #include <linux/refcount.h>
-#include <linux/rbtree.h>
 #include <linux/list.h>
 #include <stdio.h>
 #include <unistd.h>
@@ -29,11 +28,6 @@ struct lbr_stitch {
 	struct callchain_cursor_node	*prev_lbr_cursor;
 };
 
-struct thread_rb_node {
-	struct rb_node rb_node;
-	struct thread *thread;
-};
-
 DECLARE_RC_STRUCT(thread) {
 	/** @maps: mmaps associated with this thread. */
 	struct maps		*maps;
diff --git a/tools/perf/util/threads.c b/tools/perf/util/threads.c
new file mode 100644
index 000000000000..d984ec939c7b
--- /dev/null
+++ b/tools/perf/util/threads.c
@@ -0,0 +1,244 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "threads.h"
+#include "machine.h"
+#include "thread.h"
+
+struct thread_rb_node {
+	struct rb_node rb_node;
+	struct thread *thread;
+};
+
+static struct threads_table_entry *threads__table(struct threads *threads, pid_t tid)
+{
+	/* Cast it to handle tid == -1 */
+	return &threads->table[(unsigned int)tid % THREADS__TABLE_SIZE];
+}
+
+void threads__init(struct threads *threads)
+{
+	for (int i = 0; i < THREADS__TABLE_SIZE; i++) {
+		struct threads_table_entry *table = &threads->table[i];
+
+		table->entries = RB_ROOT_CACHED;
+		init_rwsem(&table->lock);
+		table->nr = 0;
+		table->last_match = NULL;
+	}
+}
+
+void threads__exit(struct threads *threads)
+{
+	threads__remove_all_threads(threads);
+	for (int i = 0; i < THREADS__TABLE_SIZE; i++) {
+		struct threads_table_entry *table = &threads->table[i];
+
+		exit_rwsem(&table->lock);
+	}
+}
+
+size_t threads__nr(struct threads *threads)
+{
+	size_t nr = 0;
+
+	for (int i = 0; i < THREADS__TABLE_SIZE; i++) {
+		struct threads_table_entry *table = &threads->table[i];
+
+		down_read(&table->lock);
+		nr += table->nr;
+		up_read(&table->lock);
+	}
+	return nr;
+}
+
+/*
+ * Front-end cache - TID lookups come in blocks,
+ * so most of the time we dont have to look up
+ * the full rbtree:
+ */
+static struct thread *__threads_table_entry__get_last_match(struct threads_table_entry *table,
+							    pid_t tid)
+{
+	struct thread *th, *res = NULL;
+
+	th = table->last_match;
+	if (th != NULL) {
+		if (thread__tid(th) == tid)
+			res = thread__get(th);
+	}
+	return res;
+}
+
+static void __threads_table_entry__set_last_match(struct threads_table_entry *table,
+						  struct thread *th)
+{
+	thread__put(table->last_match);
+	table->last_match = thread__get(th);
+}
+
+static void threads_table_entry__set_last_match(struct threads_table_entry *table,
+						struct thread *th)
+{
+	down_write(&table->lock);
+	__threads_table_entry__set_last_match(table, th);
+	up_write(&table->lock);
+}
+
+struct thread *threads__find(struct threads *threads, pid_t tid)
+{
+	struct threads_table_entry *table  = threads__table(threads, tid);
+	struct rb_node **p;
+	struct thread *res = NULL;
+
+	down_read(&table->lock);
+	res = __threads_table_entry__get_last_match(table, tid);
+	if (res)
+		return res;
+
+	p = &table->entries.rb_root.rb_node;
+	while (*p != NULL) {
+		struct rb_node *parent = *p;
+		struct thread *th = rb_entry(parent, struct thread_rb_node, rb_node)->thread;
+
+		if (thread__tid(th) == tid) {
+			res = thread__get(th);
+			break;
+		}
+
+		if (tid < thread__tid(th))
+			p = &(*p)->rb_left;
+		else
+			p = &(*p)->rb_right;
+	}
+	up_read(&table->lock);
+	if (res)
+		threads_table_entry__set_last_match(table, res);
+	return res;
+}
+
+struct thread *threads__findnew(struct threads *threads, pid_t pid, pid_t tid, bool *created)
+{
+	struct threads_table_entry *table  = threads__table(threads, tid);
+	struct rb_node **p;
+	struct rb_node *parent = NULL;
+	struct thread *res = NULL;
+	struct thread_rb_node *nd;
+	bool leftmost = true;
+
+	*created = false;
+	down_write(&table->lock);
+	p = &table->entries.rb_root.rb_node;
+	while (*p != NULL) {
+		struct thread *th;
+
+		parent = *p;
+		th = rb_entry(parent, struct thread_rb_node, rb_node)->thread;
+
+		if (thread__tid(th) == tid) {
+			__threads_table_entry__set_last_match(table, th);
+			res = thread__get(th);
+			goto out_unlock;
+		}
+
+		if (tid < thread__tid(th))
+			p = &(*p)->rb_left;
+		else {
+			leftmost = false;
+			p = &(*p)->rb_right;
+		}
+	}
+	nd = malloc(sizeof(*nd));
+	if (nd == NULL)
+		goto out_unlock;
+	res = thread__new(pid, tid);
+	if (!res)
+		free(nd);
+	else {
+		*created = true;
+		nd->thread = thread__get(res);
+		rb_link_node(&nd->rb_node, parent, p);
+		rb_insert_color_cached(&nd->rb_node, &table->entries, leftmost);
+		++table->nr;
+		__threads_table_entry__set_last_match(table, res);
+	}
+out_unlock:
+	up_write(&table->lock);
+	return res;
+}
+
+void threads__remove_all_threads(struct threads *threads)
+{
+	for (int i = 0; i < THREADS__TABLE_SIZE; i++) {
+		struct threads_table_entry *table = &threads->table[i];
+		struct rb_node *nd;
+
+		down_write(&table->lock);
+		__threads_table_entry__set_last_match(table, NULL);
+		nd = rb_first_cached(&table->entries);
+		while (nd) {
+			struct thread_rb_node *trb = rb_entry(nd, struct thread_rb_node, rb_node);
+
+			nd = rb_next(nd);
+			thread__put(trb->thread);
+			rb_erase_cached(&trb->rb_node, &table->entries);
+			RB_CLEAR_NODE(&trb->rb_node);
+			--table->nr;
+
+			free(trb);
+		}
+		assert(table->nr == 0);
+		up_write(&table->lock);
+	}
+}
+
+void threads__remove(struct threads *threads, struct thread *thread)
+{
+	struct rb_node **p;
+	struct threads_table_entry *table  = threads__table(threads, thread__tid(thread));
+	pid_t tid = thread__tid(thread);
+
+	down_write(&table->lock);
+	if (table->last_match && RC_CHK_EQUAL(table->last_match, thread))
+		__threads_table_entry__set_last_match(table, NULL);
+
+	p = &table->entries.rb_root.rb_node;
+	while (*p != NULL) {
+		struct rb_node *parent = *p;
+		struct thread_rb_node *nd = rb_entry(parent, struct thread_rb_node, rb_node);
+		struct thread *th = nd->thread;
+
+		if (RC_CHK_EQUAL(th, thread)) {
+			thread__put(nd->thread);
+			rb_erase_cached(&nd->rb_node, &table->entries);
+			RB_CLEAR_NODE(&nd->rb_node);
+			--table->nr;
+			free(nd);
+			break;
+		}
+
+		if (tid < thread__tid(th))
+			p = &(*p)->rb_left;
+		else
+			p = &(*p)->rb_right;
+	}
+	up_write(&table->lock);
+}
+
+int threads__for_each_thread(struct threads *threads,
+			     int (*fn)(struct thread *thread, void *data),
+			     void *data)
+{
+	for (int i = 0; i < THREADS__TABLE_SIZE; i++) {
+		struct threads_table_entry *table = &threads->table[i];
+		struct rb_node *nd;
+
+		for (nd = rb_first_cached(&table->entries); nd; nd = rb_next(nd)) {
+			struct thread_rb_node *trb = rb_entry(nd, struct thread_rb_node, rb_node);
+			int rc = fn(trb->thread, data);
+
+			if (rc != 0)
+				return rc;
+		}
+	}
+	return 0;
+
+}
diff --git a/tools/perf/util/threads.h b/tools/perf/util/threads.h
new file mode 100644
index 000000000000..ed67de627578
--- /dev/null
+++ b/tools/perf/util/threads.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PERF_THREADS_H
+#define __PERF_THREADS_H
+
+#include <linux/rbtree.h>
+#include "rwsem.h"
+
+struct thread;
+
+#define THREADS__TABLE_BITS	8
+#define THREADS__TABLE_SIZE	(1 << THREADS__TABLE_BITS)
+
+struct threads_table_entry {
+	struct rb_root_cached  entries;
+	struct rw_semaphore    lock;
+	unsigned int	       nr;
+	struct thread	       *last_match;
+};
+
+struct threads {
+	struct threads_table_entry table[THREADS__TABLE_SIZE];
+};
+
+void threads__init(struct threads *threads);
+void threads__exit(struct threads *threads);
+size_t threads__nr(struct threads *threads);
+struct thread *threads__find(struct threads *threads, pid_t tid);
+struct thread *threads__findnew(struct threads *threads, pid_t pid, pid_t tid, bool *created);
+void threads__remove_all_threads(struct threads *threads);
+void threads__remove(struct threads *threads, struct thread *thread);
+int threads__for_each_thread(struct threads *threads,
+			     int (*fn)(struct thread *thread, void *data),
+			     void *data);
+
+#endif	/* __PERF_THREADS_H */
-- 
2.44.0.rc1.240.g4c46232300-goog

[PATCH v2 5/6] perf threads: Switch from rbtree to hashmap

[Ian Rogers]

The rbtree provides a sorting on entries but this is unused. Switch to
using hashmap for O(1) rather than O(log n) find/insert/remove
complexity.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/threads.c | 146 ++++++++++++--------------------------
 tools/perf/util/threads.h |   6 +-
 2 files changed, 47 insertions(+), 105 deletions(-)

diff --git a/tools/perf/util/threads.c b/tools/perf/util/threads.c
index d984ec939c7b..55923be53180 100644
--- a/tools/perf/util/threads.c
+++ b/tools/perf/util/threads.c
@@ -3,25 +3,30 @@
 #include "machine.h"
 #include "thread.h"
 
-struct thread_rb_node {
-	struct rb_node rb_node;
-	struct thread *thread;
-};
-
 static struct threads_table_entry *threads__table(struct threads *threads, pid_t tid)
 {
 	/* Cast it to handle tid == -1 */
 	return &threads->table[(unsigned int)tid % THREADS__TABLE_SIZE];
 }
 
+static size_t key_hash(long key, void *ctx __maybe_unused)
+{
+	/* The table lookup removes low bit entropy, but this is just ignored here. */
+	return key;
+}
+
+static bool key_equal(long key1, long key2, void *ctx __maybe_unused)
+{
+	return key1 == key2;
+}
+
 void threads__init(struct threads *threads)
 {
 	for (int i = 0; i < THREADS__TABLE_SIZE; i++) {
 		struct threads_table_entry *table = &threads->table[i];
 
-		table->entries = RB_ROOT_CACHED;
+		hashmap__init(&table->shard, key_hash, key_equal, NULL);
 		init_rwsem(&table->lock);
-		table->nr = 0;
 		table->last_match = NULL;
 	}
 }
@@ -32,6 +37,7 @@ void threads__exit(struct threads *threads)
 	for (int i = 0; i < THREADS__TABLE_SIZE; i++) {
 		struct threads_table_entry *table = &threads->table[i];
 
+		hashmap__clear(&table->shard);
 		exit_rwsem(&table->lock);
 	}
 }
@@ -44,7 +50,7 @@ size_t threads__nr(struct threads *threads)
 		struct threads_table_entry *table = &threads->table[i];
 
 		down_read(&table->lock);
-		nr += table->nr;
+		nr += hashmap__size(&table->shard);
 		up_read(&table->lock);
 	}
 	return nr;
@@ -86,28 +92,13 @@ static void threads_table_entry__set_last_match(struct threads_table_entry *tabl
 struct thread *threads__find(struct threads *threads, pid_t tid)
 {
 	struct threads_table_entry *table  = threads__table(threads, tid);
-	struct rb_node **p;
-	struct thread *res = NULL;
+	struct thread *res;
 
 	down_read(&table->lock);
 	res = __threads_table_entry__get_last_match(table, tid);
-	if (res)
-		return res;
-
-	p = &table->entries.rb_root.rb_node;
-	while (*p != NULL) {
-		struct rb_node *parent = *p;
-		struct thread *th = rb_entry(parent, struct thread_rb_node, rb_node)->thread;
-
-		if (thread__tid(th) == tid) {
-			res = thread__get(th);
-			break;
-		}
-
-		if (tid < thread__tid(th))
-			p = &(*p)->rb_left;
-		else
-			p = &(*p)->rb_right;
+	if (!res) {
+		if (hashmap__find(&table->shard, tid, &res))
+			res = thread__get(res);
 	}
 	up_read(&table->lock);
 	if (res)
@@ -118,49 +109,25 @@ struct thread *threads__find(struct threads *threads, pid_t tid)
 struct thread *threads__findnew(struct threads *threads, pid_t pid, pid_t tid, bool *created)
 {
 	struct threads_table_entry *table  = threads__table(threads, tid);
-	struct rb_node **p;
-	struct rb_node *parent = NULL;
 	struct thread *res = NULL;
-	struct thread_rb_node *nd;
-	bool leftmost = true;
 
 	*created = false;
 	down_write(&table->lock);
-	p = &table->entries.rb_root.rb_node;
-	while (*p != NULL) {
-		struct thread *th;
-
-		parent = *p;
-		th = rb_entry(parent, struct thread_rb_node, rb_node)->thread;
-
-		if (thread__tid(th) == tid) {
-			__threads_table_entry__set_last_match(table, th);
-			res = thread__get(th);
-			goto out_unlock;
-		}
-
-		if (tid < thread__tid(th))
-			p = &(*p)->rb_left;
-		else {
-			leftmost = false;
-			p = &(*p)->rb_right;
-		}
-	}
-	nd = malloc(sizeof(*nd));
-	if (nd == NULL)
-		goto out_unlock;
 	res = thread__new(pid, tid);
-	if (!res)
-		free(nd);
-	else {
-		*created = true;
-		nd->thread = thread__get(res);
-		rb_link_node(&nd->rb_node, parent, p);
-		rb_insert_color_cached(&nd->rb_node, &table->entries, leftmost);
-		++table->nr;
-		__threads_table_entry__set_last_match(table, res);
+	if (res) {
+		if (hashmap__add(&table->shard, tid, res)) {
+			/* Add failed. Assume a race so find other entry. */
+			thread__put(res);
+			res = NULL;
+			if (hashmap__find(&table->shard, tid, &res))
+				res = thread__get(res);
+		} else {
+			res = thread__get(res);
+			*created = true;
+		}
+		if (res)
+			__threads_table_entry__set_last_match(table, res);
 	}
-out_unlock:
 	up_write(&table->lock);
 	return res;
 }
@@ -169,57 +136,32 @@ void threads__remove_all_threads(struct threads *threads)
 {
 	for (int i = 0; i < THREADS__TABLE_SIZE; i++) {
 		struct threads_table_entry *table = &threads->table[i];
-		struct rb_node *nd;
+		struct hashmap_entry *cur, *tmp;
+		size_t bkt;
 
 		down_write(&table->lock);
 		__threads_table_entry__set_last_match(table, NULL);
-		nd = rb_first_cached(&table->entries);
-		while (nd) {
-			struct thread_rb_node *trb = rb_entry(nd, struct thread_rb_node, rb_node);
-
-			nd = rb_next(nd);
-			thread__put(trb->thread);
-			rb_erase_cached(&trb->rb_node, &table->entries);
-			RB_CLEAR_NODE(&trb->rb_node);
-			--table->nr;
+		hashmap__for_each_entry_safe((&table->shard), cur, tmp, bkt) {
+			struct thread *old_value;
 
-			free(trb);
+			hashmap__delete(&table->shard, cur->key, /*old_key=*/NULL, &old_value);
+			thread__put(old_value);
 		}
-		assert(table->nr == 0);
 		up_write(&table->lock);
 	}
 }
 
 void threads__remove(struct threads *threads, struct thread *thread)
 {
-	struct rb_node **p;
 	struct threads_table_entry *table  = threads__table(threads, thread__tid(thread));
-	pid_t tid = thread__tid(thread);
+	struct thread *old_value;
 
 	down_write(&table->lock);
 	if (table->last_match && RC_CHK_EQUAL(table->last_match, thread))
 		__threads_table_entry__set_last_match(table, NULL);
 
-	p = &table->entries.rb_root.rb_node;
-	while (*p != NULL) {
-		struct rb_node *parent = *p;
-		struct thread_rb_node *nd = rb_entry(parent, struct thread_rb_node, rb_node);
-		struct thread *th = nd->thread;
-
-		if (RC_CHK_EQUAL(th, thread)) {
-			thread__put(nd->thread);
-			rb_erase_cached(&nd->rb_node, &table->entries);
-			RB_CLEAR_NODE(&nd->rb_node);
-			--table->nr;
-			free(nd);
-			break;
-		}
-
-		if (tid < thread__tid(th))
-			p = &(*p)->rb_left;
-		else
-			p = &(*p)->rb_right;
-	}
+	hashmap__delete(&table->shard, thread__tid(thread), /*old_key=*/NULL, &old_value);
+	thread__put(old_value);
 	up_write(&table->lock);
 }
 
@@ -229,11 +171,11 @@ int threads__for_each_thread(struct threads *threads,
 {
 	for (int i = 0; i < THREADS__TABLE_SIZE; i++) {
 		struct threads_table_entry *table = &threads->table[i];
-		struct rb_node *nd;
+		struct hashmap_entry *cur;
+		size_t bkt;
 
-		for (nd = rb_first_cached(&table->entries); nd; nd = rb_next(nd)) {
-			struct thread_rb_node *trb = rb_entry(nd, struct thread_rb_node, rb_node);
-			int rc = fn(trb->thread, data);
+		hashmap__for_each_entry((&table->shard), cur, bkt) {
+			int rc = fn((struct thread *)cur->pvalue, data);
 
 			if (rc != 0)
 				return rc;
diff --git a/tools/perf/util/threads.h b/tools/perf/util/threads.h
index ed67de627578..d03bd91a7769 100644
--- a/tools/perf/util/threads.h
+++ b/tools/perf/util/threads.h
@@ -2,7 +2,7 @@
 #ifndef __PERF_THREADS_H
 #define __PERF_THREADS_H
 
-#include <linux/rbtree.h>
+#include "hashmap.h"
 #include "rwsem.h"
 
 struct thread;
@@ -11,9 +11,9 @@ struct thread;
 #define THREADS__TABLE_SIZE	(1 << THREADS__TABLE_BITS)
 
 struct threads_table_entry {
-	struct rb_root_cached  entries;
+	/* Key is tid, value is struct thread. */
+	struct hashmap	       shard;
 	struct rw_semaphore    lock;
-	unsigned int	       nr;
 	struct thread	       *last_match;
 };
 
-- 
2.44.0.rc1.240.g4c46232300-goog

[PATCH v2 6/6] perf threads: Reduce table size from 256 to 8

[Ian Rogers]

The threads data structure is an array of hashmaps, previously
rbtrees. The two levels allows for a fixed outer array where access is
guarded by rw_semaphores. Commit 91e467bc568f ("perf machine: Use
hashtable for machine threads") sized the outer table at 256 entries
to avoid future scalability problems, however, this means the threads
struct is sized at 30,720 bytes. As the hashmaps allow O(1) access for
the common find/insert/remove operations, lower the number of entries
to 8. This reduces the size overhead to 960 bytes.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/threads.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/threads.h b/tools/perf/util/threads.h
index d03bd91a7769..da68d2223f18 100644
--- a/tools/perf/util/threads.h
+++ b/tools/perf/util/threads.h
@@ -7,7 +7,7 @@
 
 struct thread;
 
-#define THREADS__TABLE_BITS	8
+#define THREADS__TABLE_BITS	3
 #define THREADS__TABLE_SIZE	(1 << THREADS__TABLE_BITS)
 
 struct threads_table_entry {
-- 
2.44.0.rc1.240.g4c46232300-goog