spinlock vs mutex benchmark

spinlock.c

//
// compile with:
// gcc -O2 -o spinlock spinlock.c -lpthread && ./spinlock
//
// verification and spinlock stats can be enabled with this:
// gcc -O2 -DSPINLOCK_VERIFY_AND_STATS=1 -o spinlock spinlock.c && ./spinlock

#define _GNU_SOURCE
#define __USE_GNU

#include <pthread.h>
#include <errno.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <stddef.h>
#include <ctype.h>
#include <string.h>
#include <strings.h>
#include <arpa/inet.h>
#include <netinet/tcp.h>
#include <sys/ioctl.h>
#include <libgen.h>
#include <dirent.h>
#include <fcntl.h>
#include <getopt.h>
#include <grp.h>
#include <pwd.h>
#include <limits.h>
#include <locale.h>
#include <net/if.h>
#include <poll.h>
#include <signal.h>
#include <syslog.h>
#include <sys/mman.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/un.h>
#include <time.h>
#include <unistd.h>
#include <uuid/uuid.h>
#include <spawn.h>
#include <uv.h>
#include <assert.h>

#define likely(x) __builtin_expect(!!(x), 1)
#define unlikely(x) __builtin_expect(!!(x), 0)

#define assert_with_message(x) for ( ; !(x) ; assert(x) )

pid_t gettid(void) {
    static __thread pid_t cached_tid = -1;

    if(unlikely(cached_tid == -1))
        cached_tid = (pid_t)syscall(SYS_gettid);

    return cached_tid;
}

#define USEC_PER_SEC    1000000ULL
#define NSEC_PER_SEC    1000000000ULL
#define NSEC_PER_USEC   1000ULL
typedef unsigned long long usec_t;
usec_t now_usec(clockid_t clk_id) {
    struct timespec ts = { 0, 0 };
    if(unlikely(clock_gettime(clk_id, &ts) == -1)) {
        printf("clock_gettime(%d, &timespec) failed.\n", clk_id);
        return 0;
    }
    return (usec_t)ts.tv_sec * USEC_PER_SEC + ((ts.tv_nsec % NSEC_PER_SEC) / NSEC_PER_USEC);
}

// static const struct timespec work_duration = { .tv_sec = 0, .tv_nsec = 1 * NSEC_PER_SEC / 1000 };
static const struct timespec work_duration = { .tv_sec = 0, .tv_nsec = 0 };

size_t counter = 0;
bool stop_stress = false;

// ----------------------------------------------------------------------------
// SPINLOCK

typedef struct netdata_spinlock {
    bool locked;
#ifdef SPINLOCK_VERIFY_AND_STATS
    size_t spins;
    size_t sleeps;
    pid_t locker_pid;
#endif
} SPINLOCK;

#define NETDATA_SPINLOCK_INITIALIZER (SPINLOCK) { .locked = false }

void __netdata_spinlock_init(SPINLOCK *spinlock) {
    *spinlock = NETDATA_SPINLOCK_INITIALIZER;
}

void __netdata_spinlock_lock(SPINLOCK *spinlock) {
    static const struct timespec ns = { .tv_sec = 0, .tv_nsec = 1 };
    size_t spins = 0;
#ifdef SPINLOCK_VERIFY_AND_STATS
    size_t sleeps = 0;
#endif

    while(__atomic_test_and_set(&spinlock->locked, __ATOMIC_ACQUIRE)) {

        do {
#ifdef SPINLOCK_VERIFY_AND_STATS
            if(unlikely((++spins % 8) == 0)) {
                ++sleeps;
                nanosleep(&ns, NULL);
            }
#else
            if(unlikely(++spins == 8)) {
                spins = 0;
                nanosleep(&ns, NULL);
            }
#endif
        } while(__atomic_load_n(&spinlock->locked, __ATOMIC_RELAXED));
    }

#ifdef SPINLOCK_VERIFY_AND_STATS
    pid_t last_locker_pid = spinlock->locker_pid;
    if(last_locker_pid != 0) {
        printf("spinlock locker pid is %d, but expected it to be unlocked, my pid is %d\n", last_locker_pid, gettid());
        abort();
    }

    // we have the lock
    spinlock->locker_pid = gettid();
    spinlock->spins += spins;
    spinlock->sleeps += sleeps;
#endif
}

void __netdata_spinlock_unlock(SPINLOCK *spinlock) {
#ifdef SPINLOCK_VERIFY_AND_STATS
    pid_t last_locker_pid = spinlock->locker_pid;
    if(last_locker_pid != gettid()) {
        printf("Spinlock should be locked by my pid %d, but it is locked by pid %d\n", gettid(), last_locker_pid);
        abort();
    }

    spinlock->locker_pid = 0;
#endif

    __atomic_clear(&spinlock->locked, __ATOMIC_RELEASE);
}

SPINLOCK sp = NETDATA_SPINLOCK_INITIALIZER;

size_t stress_test_spinlock(size_t id) {
    (void)id;
    //printf(" >> Thread %zu started as tid %d\n", id, gettid());

    size_t count = 0;
    while(!__atomic_load_n(&stop_stress, __ATOMIC_RELAXED)) {
        __netdata_spinlock_lock(&sp);
        
        if(work_duration.tv_nsec || work_duration.tv_sec)
            nanosleep(&work_duration, NULL);

        counter++;
        count++;
        __netdata_spinlock_unlock(&sp);
    }

    return count;
}

// ----------------------------------------------------------------------------
// PTHREAD MUTEX

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
size_t stress_test_mutex(size_t id) {
    (void)id;
    //printf(" >> Thread %zu started as tid %d\n", id, gettid());

    size_t count = 0;
    while(!__atomic_load_n(&stop_stress, __ATOMIC_RELAXED)) {
        pthread_mutex_lock(&mutex);
        
        if(work_duration.tv_nsec || work_duration.tv_sec)
            nanosleep(&work_duration, NULL);

        counter++;
        count++;
        pthread_mutex_unlock(&mutex);
    }

    return count;
}

// ----------------------------------------------------------------------------
// PTHREAD RWLOCK

pthread_rwlock_t rwlock = PTHREAD_RWLOCK_INITIALIZER;
size_t stress_test_rwlock(size_t id) {
    (void)id;
    //printf(" >> Thread %zu started as tid %d\n", id, gettid());

    size_t count = 0;
    while(!__atomic_load_n(&stop_stress, __ATOMIC_RELAXED)) {
        pthread_rwlock_wrlock(&rwlock);
        
        if(work_duration.tv_nsec || work_duration.tv_sec)
            nanosleep(&work_duration, NULL);

        counter++;
        count++;
        pthread_rwlock_unlock(&rwlock);
    }

    return count;
}

// ----------------------------------------------------------------------------
// PTHREAD SPIN

pthread_spinlock_t pspinlock;
size_t stress_test_pspinlock(size_t id) {
    (void)id;
    //printf(" >> Thread %zu started as tid %d\n", id, gettid());

    size_t count = 0;
    while(!__atomic_load_n(&stop_stress, __ATOMIC_RELAXED)) {
        pthread_spin_lock(&pspinlock);
        
        if(work_duration.tv_nsec || work_duration.tv_sec)
            nanosleep(&work_duration, NULL);

        counter++;
        count++;
        pthread_spin_unlock(&pspinlock);
    }

    return count;
}

// ----------------------------------------------------------------------------
// stress test controller

struct worker {
    size_t (*callback)(size_t id);
    pthread_t thread;
    size_t id;
    size_t count;
    usec_t duration_ut;
    double cpu_pc;
};

void *run_worker(void *ptr) {
    pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);

    struct worker *me = ptr;

    struct rusage start_ru, end_ru;

    usec_t start_ut = now_usec(CLOCK_MONOTONIC);
    getrusage(RUSAGE_THREAD, &start_ru);

    me->count = me->callback(me->id);

    getrusage(RUSAGE_THREAD, &end_ru);
    usec_t end_ut = now_usec(CLOCK_MONOTONIC);

    me->duration_ut = end_ut - start_ut;

    unsigned long long user_cpu   = end_ru.ru_utime.tv_sec * 1000000ULL + end_ru.ru_utime.tv_usec - start_ru.ru_utime.tv_sec * 1000000ULL + start_ru.ru_utime.tv_usec;
    unsigned long long system_cpu = end_ru.ru_stime.tv_sec * 1000000ULL + end_ru.ru_stime.tv_usec - start_ru.ru_stime.tv_sec * 1000000ULL + start_ru.ru_stime.tv_usec;
    me->cpu_pc  = (double)(user_cpu + system_cpu) * 100.0 / (double)me->duration_ut;

    return me;
}

void run_test(size_t (*function)(size_t id), const char *name) {
    int threads_num[] = { 1, 2, 3, 4, 8, 16, 24, 48, 96, 128 };
    int runs = sizeof(threads_num) / sizeof(int);

    static const struct timespec ns  = { .tv_sec = 5, .tv_nsec = 0 };
 
    printf("\n%s:\n", name);
    for(int i = 0; i < runs ; i++) {
        int threads = threads_num[i];

        struct worker workers[threads];
        memset(workers, 0, sizeof(workers));

        sp = NETDATA_SPINLOCK_INITIALIZER;
        stop_stress = false;
        counter = 0;

        for(int p = 0; p < threads ;p++) {
            struct worker *w = &workers[p];
            w->callback = function;
            w->id = p;

            int ret = pthread_create(&w->thread, NULL, *run_worker, (void *)w);
            if(ret != 0) {
                fprintf(stderr, "failed to create thread %d, pthread_create() failed with code %d\n", p, ret);
                exit(1);
            }
        }

        nanosleep(&ns, NULL);
        __atomic_store_n(&stop_stress, true, __ATOMIC_RELAXED);
 
        size_t total_count = 0, min = 0, max = 0, avg = 0, deviation = 0;
        double total_cpu = 0.0;
        usec_t duration_ut = ns.tv_sec * USEC_PER_SEC;
        for(int p = 0; p < threads ;p++) {
            struct worker *w = &workers[p];

            int ret = pthread_join(w->thread, NULL);
            if(ret != 0) {
                fprintf(stderr, "failed to join thread %d, pthread_join() failed with code %d\n", p, ret);
                exit(1);
            }
            total_count += w->count;
            total_cpu += w->cpu_pc;

            if(w->duration_ut > duration_ut)
                duration_ut = w->duration_ut;

            if(!p) {
                min = w->count;
                max = w->count;
            }
            else {
                if(w->count < min)
                    min = w->count;
                if(w->count > max)
                    max = w->count;
            }
        }
        avg = total_count / threads;
        deviation = (max - min) * 100 / avg;

        printf( "Run No %3d: %3d threads, locks %10zu (%10zu %s), "
#ifdef SPINLOCK_VERIFY_AND_STATS
                "spins %10zu, sleeps %10zu, "
#endif
                "rate %8.2f Mlocks/s, cpu %8.2f %%, deviation %5zu %%\n",
            i + 1, threads, counter, total_count, (counter == total_count) ? "   OK" : "ERROR",
#ifdef SPINLOCK_VERIFY_AND_STATS
            sp.spins, sp.sleeps,
#endif
            (double)total_count / (double)duration_ut,
            total_cpu,
            deviation
        );
    }
}

int main(int argc, char **argv) {
    (void)argc; (void)argv;

    pthread_spin_init(&pspinlock, PTHREAD_PROCESS_PRIVATE);

    run_test(stress_test_spinlock, "SPINLOCK");
    run_test(stress_test_pspinlock, "PTHREAD SPIN");
    run_test(stress_test_mutex, "PTHREAD MUTEX");
    run_test(stress_test_rwlock, "PTHREAD RWLOCK");

    pthread_spin_destroy(&pspinlock);
    return 0;
}

On an RPI 4+

SPINLOCK:
Run No   1:   1 threads, locks   92182117 (  92182117    OK), rate    18.44 Mlocks/s, cpu    99.81 %, deviation     0 %
Run No   2:   2 threads, locks   59658463 (  59658463    OK), rate    11.93 Mlocks/s, cpu   191.27 %, deviation    56 %
Run No   3:   3 threads, locks   59882611 (  59882611    OK), rate    11.98 Mlocks/s, cpu   276.56 %, deviation   192 %
Run No   4:   4 threads, locks   63552957 (  63552957    OK), rate    12.70 Mlocks/s, cpu   224.98 %, deviation    64 %
Run No   5:   8 threads, locks   61393948 (  61393948    OK), rate    12.26 Mlocks/s, cpu   248.45 %, deviation    43 %
Run No   6:  16 threads, locks   61009991 (  61009991    OK), rate    12.19 Mlocks/s, cpu   285.23 %, deviation    49 %
Run No   7:  24 threads, locks   60709171 (  60709171    OK), rate    12.13 Mlocks/s, cpu   317.08 %, deviation    62 %
Run No   8:  48 threads, locks   60131966 (  60131966    OK), rate    12.01 Mlocks/s, cpu   372.52 %, deviation    78 %
Run No   9:  96 threads, locks   58410348 (  58410348    OK), rate    11.59 Mlocks/s, cpu   391.49 %, deviation   116 %
Run No  10: 128 threads, locks   56704705 (  56704705    OK), rate    11.32 Mlocks/s, cpu   390.62 %, deviation   123 %

PTHREAD SPIN:
Run No   1:   1 threads, locks   98550825 (  98550825    OK), rate    19.71 Mlocks/s, cpu    99.90 %, deviation     0 %
Run No   2:   2 threads, locks   63753623 (  63753623    OK), rate    12.75 Mlocks/s, cpu   199.43 %, deviation    35 %
Run No   3:   3 threads, locks   62321257 (  62321257    OK), rate    12.46 Mlocks/s, cpu   297.98 %, deviation   161 %
Run No   4:   4 threads, locks   61779458 (  61779458    OK), rate    12.36 Mlocks/s, cpu   389.21 %, deviation    72 %
Run No   5:   8 threads, locks   41167905 (  41167905    OK), rate     8.23 Mlocks/s, cpu   390.50 %, deviation    73 %
Run No   6:  16 threads, locks   22802569 (  22802569    OK), rate     4.53 Mlocks/s, cpu   391.58 %, deviation   188 %
Run No   7:  24 threads, locks   19540682 (  19540682    OK), rate     3.87 Mlocks/s, cpu   392.49 %, deviation   168 %
Run No   8:  48 threads, locks    8723803 (   8723803    OK), rate     1.74 Mlocks/s, cpu   396.04 %, deviation   399 %
Run No   9:  96 threads, locks    4007949 (   4007949    OK), rate     0.79 Mlocks/s, cpu   402.18 %, deviation  1672 %
Run No  10: 128 threads, locks    4631627 (   4631627    OK), rate     0.82 Mlocks/s, cpu   401.91 %, deviation  2025 %

PTHREAD MUTEX:
Run No   1:   1 threads, locks   79463948 (  79463948    OK), rate    15.89 Mlocks/s, cpu    99.64 %, deviation     0 %
Run No   2:   2 threads, locks   50387733 (  50387733    OK), rate    10.08 Mlocks/s, cpu   199.13 %, deviation    52 %
Run No   3:   3 threads, locks   34536291 (  34536291    OK), rate     6.91 Mlocks/s, cpu   271.45 %, deviation    38 %
Run No   4:   4 threads, locks   31658401 (  31658401    OK), rate     6.33 Mlocks/s, cpu   339.27 %, deviation    34 %
Run No   5:   8 threads, locks   30807647 (  30807647    OK), rate     6.16 Mlocks/s, cpu   358.45 %, deviation    55 %
Run No   6:  16 threads, locks   29003236 (  29003236    OK), rate     5.80 Mlocks/s, cpu   375.16 %, deviation    32 %
Run No   7:  24 threads, locks   28085728 (  28085728    OK), rate     5.61 Mlocks/s, cpu   382.81 %, deviation    37 %
Run No   8:  48 threads, locks   27706029 (  27706029    OK), rate     5.54 Mlocks/s, cpu   386.49 %, deviation    62 %
Run No   9:  96 threads, locks   27796542 (  27796542    OK), rate     5.50 Mlocks/s, cpu   392.30 %, deviation    97 %
Run No  10: 128 threads, locks   27495238 (  27495238    OK), rate     5.49 Mlocks/s, cpu   390.32 %, deviation    67 %

PTHREAD RWLOCK:
Run No   1:   1 threads, locks   51373623 (  51373623    OK), rate    10.27 Mlocks/s, cpu    99.39 %, deviation     0 %
Run No   2:   2 threads, locks   25639442 (  25639442    OK), rate     5.13 Mlocks/s, cpu   199.21 %, deviation    22 %
Run No   3:   3 threads, locks   20128989 (  20128989    OK), rate     4.03 Mlocks/s, cpu   291.42 %, deviation    66 %
Run No   4:   4 threads, locks   20635529 (  20635529    OK), rate     4.11 Mlocks/s, cpu   372.38 %, deviation    27 %
Run No   5:   8 threads, locks   16451104 (  16451104    OK), rate     3.29 Mlocks/s, cpu   374.42 %, deviation    26 %
Run No   6:  16 threads, locks    9515592 (   9515592    OK), rate     1.90 Mlocks/s, cpu   384.34 %, deviation    75 %
Run No   7:  24 threads, locks    8266489 (   8266489    OK), rate     1.64 Mlocks/s, cpu   384.88 %, deviation   118 %
Run No   8:  48 threads, locks    3699839 (   3699839    OK), rate     0.74 Mlocks/s, cpu   392.39 %, deviation   219 %
Run No   9:  96 threads, locks    2860329 (   2860329    OK), rate     0.56 Mlocks/s, cpu   398.97 %, deviation   359 %
Run No  10: 128 threads, locks    1474116 (   1474116    OK), rate     0.29 Mlocks/s, cpu   404.24 %, deviation   405 %

AMD EPYC 7453 28-Core Processor x 2 processors (not an idle machine)

SPINLOCK:
Run No   1:   1 threads, locks 1326569716 (1326569716    OK), rate   265.31 Mlocks/s, cpu    99.94 %, deviation     0 %
Run No   2:   2 threads, locks 1286590410 (1286590410    OK), rate   257.31 Mlocks/s, cpu   108.32 %, deviation    12 %
Run No   3:   3 threads, locks 1280099869 (1280099869    OK), rate   256.01 Mlocks/s, cpu   114.07 %, deviation    16 %
Run No   4:   4 threads, locks 1266448441 (1266448441    OK), rate   253.28 Mlocks/s, cpu   120.24 %, deviation    15 %
Run No   5:   8 threads, locks 1216662420 (1216662420    OK), rate   243.32 Mlocks/s, cpu   145.78 %, deviation    21 %
Run No   6:  16 threads, locks 1143276728 (1143276728    OK), rate   228.63 Mlocks/s, cpu   194.09 %, deviation    17 %
Run No   7:  24 threads, locks 1075294625 (1075294625    OK), rate   215.03 Mlocks/s, cpu   246.64 %, deviation    27 %
Run No   8:  48 threads, locks  906365377 ( 906365377    OK), rate   181.23 Mlocks/s, cpu   402.08 %, deviation    30 %
Run No   9:  96 threads, locks  639875022 ( 639875022    OK), rate   127.86 Mlocks/s, cpu   759.73 %, deviation    56 %
Run No  10: 128 threads, locks  509513168 ( 509513168    OK), rate   101.68 Mlocks/s, cpu  1065.38 %, deviation    65 %

PTHREAD SPIN:
Run No   1:   1 threads, locks  836470739 ( 836470739    OK), rate   167.29 Mlocks/s, cpu    99.97 %, deviation     0 %
Run No   2:   2 threads, locks  129801675 ( 129801675    OK), rate    25.96 Mlocks/s, cpu   199.67 %, deviation    48 %
Run No   3:   3 threads, locks   72699405 (  72699405    OK), rate    14.54 Mlocks/s, cpu   299.75 %, deviation    24 %
Run No   4:   4 threads, locks   56771941 (  56771941    OK), rate    11.35 Mlocks/s, cpu   399.80 %, deviation    61 %
Run No   5:   8 threads, locks   36946464 (  36946464    OK), rate     7.39 Mlocks/s, cpu   799.49 %, deviation   147 %
Run No   6:  16 threads, locks   22213483 (  22213483    OK), rate     4.44 Mlocks/s, cpu  1598.50 %, deviation   238 %
Run No   7:  24 threads, locks   18294873 (  18294873    OK), rate     3.66 Mlocks/s, cpu  2397.35 %, deviation   201 %
Run No   8:  48 threads, locks   12448019 (  12448019    OK), rate     2.49 Mlocks/s, cpu  4739.11 %, deviation   646 %
Run No   9:  96 threads, locks    6482798 (   6482798    OK), rate     1.29 Mlocks/s, cpu  8355.59 %, deviation   288 %
Run No  10: 128 threads, locks    4678594 (   4678594    OK), rate     0.93 Mlocks/s, cpu  8336.90 %, deviation   449 %

PTHREAD MUTEX:
Run No   1:   1 threads, locks  592234293 ( 592234293    OK), rate   118.44 Mlocks/s, cpu    99.91 %, deviation     0 %
Run No   2:   2 threads, locks  169372770 ( 169372770    OK), rate    33.87 Mlocks/s, cpu   190.04 %, deviation    34 %
Run No   3:   3 threads, locks  149135010 ( 149135010    OK), rate    29.83 Mlocks/s, cpu   277.78 %, deviation    16 %
Run No   4:   4 threads, locks  137290923 ( 137290923    OK), rate    27.46 Mlocks/s, cpu   372.87 %, deviation    17 %
Run No   5:   8 threads, locks  139647828 ( 139647828    OK), rate    27.93 Mlocks/s, cpu   766.50 %, deviation    14 %
Run No   6:  16 threads, locks  138530171 ( 138530171    OK), rate    27.70 Mlocks/s, cpu  1561.10 %, deviation    53 %
Run No   7:  24 threads, locks  135833156 ( 135833156    OK), rate    27.16 Mlocks/s, cpu  2341.83 %, deviation    41 %
Run No   8:  48 threads, locks  125167604 ( 125167604    OK), rate    25.03 Mlocks/s, cpu  4533.17 %, deviation    60 %
Run No   9:  96 threads, locks  122419292 ( 122419292    OK), rate    24.47 Mlocks/s, cpu  7532.81 %, deviation    44 %
Run No  10: 128 threads, locks  119881917 ( 119881917    OK), rate    23.95 Mlocks/s, cpu  7419.06 %, deviation    41 %

PTHREAD RWLOCK:
Run No   1:   1 threads, locks  577515489 ( 577515489    OK), rate   115.50 Mlocks/s, cpu    99.97 %, deviation     0 %
Run No   2:   2 threads, locks   70897773 (  70897773    OK), rate    14.18 Mlocks/s, cpu   197.97 %, deviation     2 %
Run No   3:   3 threads, locks  100096016 ( 100096016    OK), rate    20.02 Mlocks/s, cpu   269.59 %, deviation     4 %
Run No   4:   4 threads, locks   73535306 (  73535306    OK), rate    14.71 Mlocks/s, cpu   357.71 %, deviation    11 %
Run No   5:   8 threads, locks   65474954 (  65474954    OK), rate    13.09 Mlocks/s, cpu   734.34 %, deviation    14 %
Run No   6:  16 threads, locks   62848407 (  62848407    OK), rate    12.57 Mlocks/s, cpu  1508.38 %, deviation    25 %
Run No   7:  24 threads, locks   57507160 (  57507160    OK), rate    11.50 Mlocks/s, cpu  2262.38 %, deviation    12 %
Run No   8:  48 threads, locks   56545326 (  56545326    OK), rate    11.31 Mlocks/s, cpu  4475.63 %, deviation    40 %
Run No   9:  96 threads, locks   25148992 (  25148992    OK), rate     5.02 Mlocks/s, cpu  7403.88 %, deviation    35 %
Run No  10: 128 threads, locks   15254280 (  15254280    OK), rate     3.05 Mlocks/s, cpu  7664.81 %, deviation    65 %