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background_thread: add max thread count config

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Looking at the thread counts in our services, jemalloc's background thread
is useful, but mostly idle.  Add a config option to tune down the number of threads.
This commit is contained in:
Dave Watson
2018-03-29 12:58:13 -07:00
parent 4be74d5112
commit 8b14f3abc0
7 changed files with 177 additions and 22 deletions
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49
src/background_thread.c
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@@ -11,12 +11,14 @@
#define BACKGROUND_THREAD_DEFAULT false
/* Read-only after initialization. */
bool opt_background_thread = BACKGROUND_THREAD_DEFAULT;
size_t opt_max_background_threads = MAX_BACKGROUND_THREAD_LIMIT;
/* Used for thread creation, termination and stats. */
malloc_mutex_t background_thread_lock;
/* Indicates global state. Atomic because decay reads this w/o locking. */
atomic_b_t background_thread_enabled_state;
size_t n_background_threads;
size_t max_background_threads;
/* Thread info per-index. */
background_thread_info_t *background_thread_info;
@@ -287,7 +289,7 @@ background_work_sleep_once(tsdn_t *tsdn, background_thread_info_t *info, unsigne
uint64_t min_interval = BACKGROUND_THREAD_INDEFINITE_SLEEP;
unsigned narenas = narenas_total_get();
for (unsigned i = ind; i < narenas; i += ncpus) {
for (unsigned i = ind; i < narenas; i += max_background_threads) {
arena_t *arena = arena_get(tsdn, i, false);
if (!arena) {
continue;
@@ -390,7 +392,7 @@ check_background_thread_creation(tsd_t *tsd, unsigned *n_created,
tsdn_t *tsdn = tsd_tsdn(tsd);
malloc_mutex_unlock(tsdn, &background_thread_info[0].mtx);
for (unsigned i = 1; i < ncpus; i++) {
for (unsigned i = 1; i < max_background_threads; i++) {
if (created_threads[i]) {
continue;
}
@@ -430,9 +432,9 @@ check_background_thread_creation(tsd_t *tsd, unsigned *n_created,
static void
background_thread0_work(tsd_t *tsd) {
/* Thread0 is also responsible for launching / terminating threads. */
VARIABLE_ARRAY(bool, created_threads, ncpus);
VARIABLE_ARRAY(bool, created_threads, max_background_threads);
unsigned i;
for (i = 1; i < ncpus; i++) {
for (i = 1; i < max_background_threads; i++) {
created_threads[i] = false;
}
/* Start working, and create more threads when asked. */
@@ -455,7 +457,7 @@ background_thread0_work(tsd_t *tsd) {
* the global background_thread mutex (and is waiting) for us.
*/
assert(!background_thread_enabled());
for (i = 1; i < ncpus; i++) {
for (i = 1; i < max_background_threads; i++) {
background_thread_info_t *info = &background_thread_info[i];
assert(info->state != background_thread_paused);
if (created_threads[i]) {
@@ -502,7 +504,7 @@ background_work(tsd_t *tsd, unsigned ind) {
static void *
background_thread_entry(void *ind_arg) {
unsigned thread_ind = (unsigned)(uintptr_t)ind_arg;
assert(thread_ind < ncpus);
assert(thread_ind < max_background_threads);
#ifdef JEMALLOC_HAVE_PTHREAD_SETNAME_NP
pthread_setname_np(pthread_self(), "jemalloc_bg_thd");
#endif
@@ -536,7 +538,7 @@ background_thread_create(tsd_t *tsd, unsigned arena_ind) {
malloc_mutex_assert_owner(tsd_tsdn(tsd), &background_thread_lock);
/* We create at most NCPUs threads. */
size_t thread_ind = arena_ind % ncpus;
size_t thread_ind = arena_ind % max_background_threads;
background_thread_info_t *info = &background_thread_info[thread_ind];
bool need_new_thread;
@@ -590,9 +592,9 @@ background_threads_enable(tsd_t *tsd) {
assert(background_thread_enabled());
malloc_mutex_assert_owner(tsd_tsdn(tsd), &background_thread_lock);
VARIABLE_ARRAY(bool, marked, ncpus);
VARIABLE_ARRAY(bool, marked, max_background_threads);
unsigned i, nmarked;
for (i = 0; i < ncpus; i++) {
for (i = 0; i < max_background_threads; i++) {
marked[i] = false;
}
nmarked = 0;
@@ -601,18 +603,18 @@ background_threads_enable(tsd_t *tsd) {
/* Mark the threads we need to create for thread 0. */
unsigned n = narenas_total_get();
for (i = 1; i < n; i++) {
if (marked[i % ncpus] ||
if (marked[i % max_background_threads] ||
arena_get(tsd_tsdn(tsd), i, false) == NULL) {
continue;
}
background_thread_info_t *info = &background_thread_info[
i % ncpus];
i % max_background_threads];
malloc_mutex_lock(tsd_tsdn(tsd), &info->mtx);
assert(info->state == background_thread_stopped);
background_thread_init(tsd, info);
malloc_mutex_unlock(tsd_tsdn(tsd), &info->mtx);
marked[i % ncpus] = true;
if (++nmarked == ncpus) {
marked[i % max_background_threads] = true;
if (++nmarked == max_background_threads) {
break;
}
}
@@ -727,14 +729,14 @@ background_thread_prefork0(tsdn_t *tsdn) {
void
background_thread_prefork1(tsdn_t *tsdn) {
for (unsigned i = 0; i < ncpus; i++) {
for (unsigned i = 0; i < max_background_threads; i++) {
malloc_mutex_prefork(tsdn, &background_thread_info[i].mtx);
}
}
void
background_thread_postfork_parent(tsdn_t *tsdn) {
for (unsigned i = 0; i < ncpus; i++) {
for (unsigned i = 0; i < max_background_threads; i++) {
malloc_mutex_postfork_parent(tsdn,
&background_thread_info[i].mtx);
}
@@ -743,7 +745,7 @@ background_thread_postfork_parent(tsdn_t *tsdn) {
void
background_thread_postfork_child(tsdn_t *tsdn) {
for (unsigned i = 0; i < ncpus; i++) {
for (unsigned i = 0; i < max_background_threads; i++) {
malloc_mutex_postfork_child(tsdn,
&background_thread_info[i].mtx);
}
@@ -756,7 +758,7 @@ background_thread_postfork_child(tsdn_t *tsdn) {
malloc_mutex_lock(tsdn, &background_thread_lock);
n_background_threads = 0;
background_thread_enabled_set(tsdn, false);
for (unsigned i = 0; i < ncpus; i++) {
for (unsigned i = 0; i < max_background_threads; i++) {
background_thread_info_t *info = &background_thread_info[i];
malloc_mutex_lock(tsdn, &info->mtx);
info->state = background_thread_stopped;
@@ -780,7 +782,7 @@ background_thread_stats_read(tsdn_t *tsdn, background_thread_stats_t *stats) {
stats->num_threads = n_background_threads;
uint64_t num_runs = 0;
nstime_init(&stats->run_interval, 0);
for (unsigned i = 0; i < ncpus; i++) {
for (unsigned i = 0; i < max_background_threads; i++) {
background_thread_info_t *info = &background_thread_info[i];
malloc_mutex_lock(tsdn, &info->mtx);
if (info->state != background_thread_stopped) {
@@ -848,6 +850,12 @@ background_thread_boot1(tsdn_t *tsdn) {
assert(have_background_thread);
assert(narenas_total_get() > 0);
if (opt_max_background_threads == MAX_BACKGROUND_THREAD_LIMIT &&
ncpus < MAX_BACKGROUND_THREAD_LIMIT) {
opt_max_background_threads = ncpus;
}
max_background_threads = opt_max_background_threads;
background_thread_enabled_set(tsdn, opt_background_thread);
if (malloc_mutex_init(&background_thread_lock,
"background_thread_global",
@@ -857,12 +865,13 @@ background_thread_boot1(tsdn_t *tsdn) {
}
background_thread_info = (background_thread_info_t *)base_alloc(tsdn,
b0get(), ncpus * sizeof(background_thread_info_t), CACHELINE);
b0get(), opt_max_background_threads *
sizeof(background_thread_info_t), CACHELINE);
if (background_thread_info == NULL) {
return true;
}
for (unsigned i = 0; i < ncpus; i++) {
for (unsigned i = 0; i < max_background_threads; i++) {
background_thread_info_t *info = &background_thread_info[i];
/* Thread mutex is rank_inclusive because of thread0. */
if (malloc_mutex_init(&info->mtx, "background_thread",