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Date: Mon, 26 Feb 2024 23:24:27 -0800
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>, Oliver Upton <oliver.upton@...ux.dev>,
Yang Jihong <yangjihong1@...wei.com>, linux-kernel@...r.kernel.org,
linux-perf-users@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v1 4/6] perf threads: Move threads to its own files
On Mon, Feb 26, 2024 at 11:07 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> On Tue, Feb 13, 2024 at 10:37 PM Ian Rogers <irogers@...gle.com> wrote:
> >
> > 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.
> >
> > Locking discipline is tightened up in this change.
>
> Doesn't look like a simple code move. Can we split the locking
> change from the move to make the reviewer's life a bit easier? :)
Not sure I follow. Take threads_nr as an example.
The old code is in machine.c, so:
-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;
-}
The new code is in threads.c:
+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;
+}
So it is a copy paste from one file to the other. The only difference
is that the old code failed to take a lock when reading "nr" so the
locking is added. I wanted to make sure all the functions in threads.c
were properly correct wrt locking, semaphore creation and destruction,
etc. We could have a broken threads.c and fix it in the next change,
but given that's a bug it could make bisection more difficult.
Ultimately I thought the locking changes were small enough to not
warrant being on their own compared to the advantages of having a sane
threads abstraction.
Thanks,
Ian
> Thanks,
> Namhyung
>
> >
> > Signed-off-by: Ian Rogers <irogers@...gle.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 8027f450fa3e..a0e8cd68d490 100644
> > --- a/tools/perf/util/Build
> > +++ b/tools/perf/util/Build
> > @@ -71,6 +71,7 @@ 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 0df775b5c110..4b8f3e9e513b 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>
> > @@ -30,11 +29,6 @@ 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 */
> > --
> > 2.43.0.687.g38aa6559b0-goog
> >
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