From 412a2ff473ac01b195eb38c0853ce065b524b2e2 Mon Sep 17 00:00:00 2001 From: Ian Rogers Date: Thu, 29 Feb 2024 21:36:44 -0800 Subject: [PATCH] perf threads: Switch from rbtree to hashmap 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 Acked-by: Namhyung Kim Cc: Yang Jihong Cc: Oliver Upton Signed-off-by: Namhyung Kim Link: https://lore.kernel.org/r/20240301053646.1449657-7-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 db52d233c2de..ff2b169e0085 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); + hashmap__for_each_entry_safe((&table->shard), cur, tmp, bkt) { + struct thread *old_value; - 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); + 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); } @@ -229,12 +171,12 @@ 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; down_read(&table->lock); - 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) { up_read(&table->lock); 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 +#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; };