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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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23
doc/jemalloc.xml.in
View File

@ -761,6 +761,18 @@ mallctl("arena." STRINGIFY(MALLCTL_ARENAS_ALL) ".decay",
selected pthread-based platforms.</para></listitem>
</varlistentry>
<varlistentry id="max_background_threads">
<term>
<mallctl>max_background_threads</mallctl>
(<type>size_t</type>)
<literal>rw</literal>
</term>
<listitem><para>Maximum number of background worker threads that will
be created. This value is capped at <link
linkend="opt.max_background_threads"><mallctl>opt.max_background_threads</mallctl></link> at
startup.</para></listitem>
</varlistentry>
<varlistentry id="config.cache_oblivious">
<term>
<mallctl>config.cache_oblivious</mallctl>
@ -1009,6 +1021,17 @@ mallctl("arena." STRINGIFY(MALLCTL_ARENAS_ALL) ".decay",
default.</para></listitem>
</varlistentry>
<varlistentry id="opt.max_background_threads">
<term>
<mallctl>opt.max_background_threads</mallctl>
(<type>const size_t</type>)
<literal>r-</literal>
</term>
<listitem><para>Maximum number of background threads that will be created
if <link linkend="background_thread">background_thread</link> is set.
Defaults to number of cpus.</para></listitem>
</varlistentry>
<varlistentry id="opt.dirty_decay_ms">
<term>
<mallctl>opt.dirty_decay_ms</mallctl>

2
include/jemalloc/internal/background_thread_externs.h
View File

@ -2,9 +2,11 @@
#define JEMALLOC_INTERNAL_BACKGROUND_THREAD_EXTERNS_H
extern bool opt_background_thread;
extern size_t opt_max_background_threads;
extern malloc_mutex_t background_thread_lock;
extern atomic_b_t background_thread_enabled_state;
extern size_t n_background_threads;
extern size_t max_background_threads;
extern background_thread_info_t *background_thread_info;
extern bool can_enable_background_thread;

1
include/jemalloc/internal/background_thread_structs.h
View File

@ -8,6 +8,7 @@
#endif
#define BACKGROUND_THREAD_INDEFINITE_SLEEP UINT64_MAX
#define MAX_BACKGROUND_THREAD_LIMIT MALLOCX_ARENA_LIMIT
typedef enum {
background_thread_stopped,

49
src/background_thread.c
View File

@ -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",

70
src/ctl.c
View File

@ -57,6 +57,7 @@ static const ctl_named_node_t *n##_index(tsdn_t *tsdn, \
CTL_PROTO(version)
CTL_PROTO(epoch)
CTL_PROTO(background_thread)
CTL_PROTO(max_background_threads)
CTL_PROTO(thread_tcache_enabled)
CTL_PROTO(thread_tcache_flush)
CTL_PROTO(thread_prof_name)
@ -85,6 +86,7 @@ CTL_PROTO(opt_dss)
CTL_PROTO(opt_narenas)
CTL_PROTO(opt_percpu_arena)
CTL_PROTO(opt_background_thread)
CTL_PROTO(opt_max_background_threads)
CTL_PROTO(opt_dirty_decay_ms)
CTL_PROTO(opt_muzzy_decay_ms)
CTL_PROTO(opt_stats_print)
@ -284,6 +286,7 @@ static const ctl_named_node_t opt_node[] = {
{NAME("narenas"), CTL(opt_narenas)},
{NAME("percpu_arena"), CTL(opt_percpu_arena)},
{NAME("background_thread"), CTL(opt_background_thread)},
{NAME("max_background_threads"), CTL(opt_max_background_threads)},
{NAME("dirty_decay_ms"), CTL(opt_dirty_decay_ms)},
{NAME("muzzy_decay_ms"), CTL(opt_muzzy_decay_ms)},
{NAME("stats_print"), CTL(opt_stats_print)},
@ -535,6 +538,7 @@ static const ctl_named_node_t root_node[] = {
{NAME("version"), CTL(version)},
{NAME("epoch"), CTL(epoch)},
{NAME("background_thread"), CTL(background_thread)},
{NAME("max_background_threads"), CTL(max_background_threads)},
{NAME("thread"), CHILD(named, thread)},
{NAME("config"), CHILD(named, config)},
{NAME("opt"), CHILD(named, opt)},
@ -1564,6 +1568,71 @@ label_return:
return ret;
}
static int
max_background_threads_ctl(tsd_t *tsd, const size_t *mib, size_t miblen,
void *oldp, size_t *oldlenp, void *newp, size_t newlen) {
int ret;
size_t oldval;
if (!have_background_thread) {
return ENOENT;
}
background_thread_ctl_init(tsd_tsdn(tsd));
malloc_mutex_lock(tsd_tsdn(tsd), &ctl_mtx);
malloc_mutex_lock(tsd_tsdn(tsd), &background_thread_lock);
if (newp == NULL) {
oldval = max_background_threads;
READ(oldval, size_t);
} else {
if (newlen != sizeof(size_t)) {
ret = EINVAL;
goto label_return;
}
oldval = max_background_threads;
READ(oldval, size_t);
size_t newval = *(size_t *)newp;
if (newval == oldval) {
ret = 0;
goto label_return;
}
if (newval > opt_max_background_threads) {
ret = EINVAL;
goto label_return;
}
if (background_thread_enabled()) {
if (!can_enable_background_thread) {
malloc_printf("<jemalloc>: Error in dlsym("
"RTLD_NEXT, \"pthread_create\"). Cannot "
"enable background_thread\n");
ret = EFAULT;
goto label_return;
}
background_thread_enabled_set(tsd_tsdn(tsd), false);
if (background_threads_disable(tsd)) {
ret = EFAULT;
goto label_return;
}
max_background_threads = newval;
background_thread_enabled_set(tsd_tsdn(tsd), true);
if (background_threads_enable(tsd)) {
ret = EFAULT;
goto label_return;
}
} else {
max_background_threads = newval;
}
}
ret = 0;
label_return:
malloc_mutex_unlock(tsd_tsdn(tsd), &background_thread_lock);
malloc_mutex_unlock(tsd_tsdn(tsd), &ctl_mtx);
return ret;
}
/******************************************************************************/
CTL_RO_CONFIG_GEN(config_cache_oblivious, bool)
@ -1590,6 +1659,7 @@ CTL_RO_NL_GEN(opt_narenas, opt_narenas, unsigned)
CTL_RO_NL_GEN(opt_percpu_arena, percpu_arena_mode_names[opt_percpu_arena],
const char *)
CTL_RO_NL_GEN(opt_background_thread, opt_background_thread, bool)
CTL_RO_NL_GEN(opt_max_background_threads, opt_max_background_threads, size_t)
CTL_RO_NL_GEN(opt_dirty_decay_ms, opt_dirty_decay_ms, ssize_t)
CTL_RO_NL_GEN(opt_muzzy_decay_ms, opt_muzzy_decay_ms, ssize_t)
CTL_RO_NL_GEN(opt_stats_print, opt_stats_print, bool)

4
src/jemalloc.c
View File

@ -1175,6 +1175,10 @@ malloc_conf_init(void) {
}
CONF_HANDLE_BOOL(opt_background_thread,
"background_thread");
CONF_HANDLE_SIZE_T(opt_max_background_threads,
"max_background_threads", 1,
opt_max_background_threads, yes, yes,
true);
if (config_prof) {
CONF_HANDLE_BOOL(opt_prof, "prof")
CONF_HANDLE_CHAR_P(opt_prof_prefix,

50
test/unit/background_thread_enable.c
View File

@ -1,6 +1,6 @@
#include "test/jemalloc_test.h"
const char *malloc_conf = "background_thread:false,narenas:1";
const char *malloc_conf = "background_thread:false,narenas:1,max_background_threads:20";
TEST_BEGIN(test_deferred) {
test_skip_if(!have_background_thread);
@ -30,8 +30,54 @@ TEST_BEGIN(test_deferred) {
}
TEST_END
TEST_BEGIN(test_max_background_threads) {
test_skip_if(!have_background_thread);
size_t maxt;
size_t opt_maxt;
size_t sz_m = sizeof(maxt);
assert_d_eq(mallctl("opt.max_background_threads",
&opt_maxt, &sz_m, NULL, 0), 0,
"Failed to get opt.max_background_threads");
assert_d_eq(mallctl("max_background_threads", &maxt, &sz_m, NULL, 0), 0,
"Failed to get max background threads");
assert_zu_eq(20, maxt, "should be ncpus");
assert_zu_eq(opt_maxt, maxt,
"max_background_threads and "
"opt.max_background_threads should match");
assert_d_eq(mallctl("max_background_threads", NULL, NULL, &maxt, sz_m),
0, "Failed to set max background threads");
unsigned id;
size_t sz_u = sizeof(unsigned);
for (unsigned i = 0; i < 10 * ncpus; i++) {
assert_d_eq(mallctl("arenas.create", &id, &sz_u, NULL, 0), 0,
"Failed to create arena");
}
bool enable = true;
size_t sz_b = sizeof(bool);
assert_d_eq(mallctl("background_thread", NULL, NULL, &enable, sz_b), 0,
"Failed to enable background threads");
assert_zu_eq(n_background_threads, maxt,
"Number of background threads should be 3.\n");
maxt = 10;
assert_d_eq(mallctl("max_background_threads", NULL, NULL, &maxt, sz_m),
0, "Failed to set max background threads");
assert_zu_eq(n_background_threads, maxt,
"Number of background threads should be 10.\n");
maxt = 3;
assert_d_eq(mallctl("max_background_threads", NULL, NULL, &maxt, sz_m),
0, "Failed to set max background threads");
assert_zu_eq(n_background_threads, maxt,
"Number of background threads should be 3.\n");
}
TEST_END
int
main(void) {
return test_no_reentrancy(
test_deferred);
test_deferred,
test_max_background_threads);
}