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posix semaphores patch

May 04, 2011 06:50AM
Прилагаемый патч использует ожидание на POSIX семафорах при доступе
к разделяемой памяти. Должно помочь уменьшить потребление процессора
при старте или он-лайн апгрэйде конфигураций с большими кэшами или
большим числом рабочих процессов.

Тестировалось на FreeBSD 8.2. На FreeBSD до версий 7.2 тестировать смысла
нет - там семафоры нерабочие. На 7.2+ нужно убедиться, что семафоров
достаточно: "sysctl p1003_1b.sem_nsems_max". По умолчанию их 32.
На 8.2+ их можно увеличивать на лету. На каждую зону нужно по одному
семафору. Текущее число семафоров можно увидеть с помощью
sysctl p1003_1b.nsems

Интересно также протестировать на других платформах - Линуксе и Солярисе.
В логах стоит обратить внимание на alert'ы.
nginx не удаляет семафоры по завершении работы. По идее, они должны
автоматически удаляться ядром. На это тоже нужно обратить внимание.


--
Игорь Сысоев
http://sysoev.ru
Index: src/event/ngx_event.c
===================================================================
--- src/event/ngx_event.c (revision 3907)
+++ src/event/ngx_event.c (working copy)
@@ -519,6 +519,7 @@
shared = shm.addr;

ngx_accept_mutex_ptr = (ngx_atomic_t *) shared;
+ ngx_accept_mutex.spin = (ngx_uint_t) -1;

if (ngx_shmtx_create(&ngx_accept_mutex, shared, cycle->lock_file.data)
!= NGX_OK)
Index: src/os/unix/ngx_posix_config.h
===================================================================
--- src/os/unix/ngx_posix_config.h (revision 3907)
+++ src/os/unix/ngx_posix_config.h (working copy)
@@ -96,6 +96,11 @@
#include <ngx_auto_config.h>


+#if (NGX_HAVE_POSIX_SEM)
+#include <semaphore.h>
+#endif
+
+
#if (NGX_HAVE_POLL)
#include <poll.h>
#endif
Index: src/os/unix/ngx_linux_config.h
===================================================================
--- src/os/unix/ngx_linux_config.h (revision 3907)
+++ src/os/unix/ngx_linux_config.h (working copy)
@@ -58,6 +58,11 @@
#include <ngx_auto_config.h>


+#if (NGX_HAVE_POSIX_SEM)
+#include <semaphore.h>
+#endif
+
+
#if (NGX_HAVE_SYS_PRCTL_H)
#include <sys/prctl.h>
#endif
Index: src/os/unix/ngx_freebsd_config.h
===================================================================
--- src/os/unix/ngx_freebsd_config.h (revision 3907)
+++ src/os/unix/ngx_freebsd_config.h (working copy)
@@ -68,6 +68,11 @@
#include <ngx_auto_config.h>


+#if (NGX_HAVE_POSIX_SEM)
+#include <semaphore.h>
+#endif
+
+
#if (NGX_HAVE_POLL)
#include <poll.h>
#endif
Index: src/os/unix/ngx_solaris_config.h
===================================================================
--- src/os/unix/ngx_solaris_config.h (revision 3907)
+++ src/os/unix/ngx_solaris_config.h (working copy)
@@ -57,6 +57,11 @@
#include <ngx_auto_config.h>


+#if (NGX_HAVE_POSIX_SEM)
+#include <semaphore.h>
+#endif
+
+
#if (NGX_HAVE_POLL)
#include <poll.h>
#endif
Index: src/os/unix/ngx_darwin_config.h
===================================================================
--- src/os/unix/ngx_darwin_config.h (revision 3907)
+++ src/os/unix/ngx_darwin_config.h (working copy)
@@ -56,6 +56,11 @@
#include <ngx_auto_config.h>


+#if (NGX_HAVE_POSIX_SEM)
+#include <semaphore.h>
+#endif
+
+
#if (NGX_HAVE_POLL)
#include <poll.h>
#endif
Index: src/core/ngx_shmtx.c
===================================================================
--- src/core/ngx_shmtx.c (revision 3907)
+++ src/core/ngx_shmtx.c (working copy)
@@ -16,9 +16,160 @@
{
mtx->lock = addr;

+ if (mtx->spin == (ngx_uint_t) -1) {
+ return NGX_OK;
+ }
+
+ mtx->spin = 2048;
+
+#if (NGX_HAVE_POSIX_SEM)
+
+ if (sem_init(&mtx->sem, 1, 0) == -1) {
+ ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, ngx_errno,
+ "sem_init() failed");
+ } else {
+ mtx->semaphore = 1;
+ }
+
+#endif
+
return NGX_OK;
}

+
+void
+ngx_shmtx_destory(ngx_shmtx_t *mtx)
+{
+#if (NGX_HAVE_POSIX_SEM)
+
+ if (mtx->semaphore) {
+ if (sem_destroy(&mtx->sem) == -1) {
+ ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, ngx_errno,
+ "sem_destroy() failed");
+ }
+ }
+
+#endif
+}
+
+
+ngx_uint_t
+ngx_shmtx_trylock(ngx_shmtx_t *mtx)
+{
+ ngx_atomic_uint_t val;
+
+ val = *mtx->lock;
+
+ return ((val & 0x80000000) == 0
+ && ngx_atomic_cmp_set(mtx->lock, val, val | 0x80000000));
+}
+
+
+void
+ngx_shmtx_lock(ngx_shmtx_t *mtx)
+{
+ ngx_uint_t i, n;
+ ngx_atomic_uint_t val;
+
+ ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0, "shmtx lock");
+
+ for ( ;; ) {
+
+ val = *mtx->lock;
+
+ if ((val & 0x80000000) == 0
+ && ngx_atomic_cmp_set(mtx->lock, val, val | 0x80000000))
+ {
+ return;
+ }
+
+ if (ngx_ncpu > 1) {
+
+ for (n = 1; n < mtx->spin; n <<= 1) {
+
+ for (i = 0; i < n; i++) {
+ ngx_cpu_pause();
+ }
+
+ val = *mtx->lock;
+
+ if ((val & 0x80000000) == 0
+ && ngx_atomic_cmp_set(mtx->lock, val, val | 0x80000000))
+ {
+ return;
+ }
+ }
+ }
+
+#if (NGX_HAVE_POSIX_SEM)
+
+ if (mtx->semaphore) {
+ val = *mtx->lock;
+
+ if ((val & 0x80000000)
+ && ngx_atomic_cmp_set(mtx->lock, val, val + 1))
+ {
+ ngx_log_debug1(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0,
+ "shmtx wait %XA", val);
+
+ if (sem_wait(&mtx->sem) == -1) {
+ ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, ngx_errno,
+ "sem_wait() failed while waiting on shmtx");
+ }
+
+ ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0,
+ "shmtx awoke");
+
+ continue;
+ }
+ }
+
+#endif
+
+ ngx_sched_yield();
+ }
+}
+
+
+void
+ngx_shmtx_unlock(ngx_shmtx_t *mtx)
+{
+ ngx_atomic_uint_t val, old, wait;
+
+ if (mtx->spin != (ngx_uint_t) -1) {
+ ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0, "shmtx unlock");
+ }
+
+ for ( ;; ) {
+
+ old = *mtx->lock;
+ wait = old & 0x7fffffff;
+ val = wait ? wait - 1 : 0;
+
+ if (ngx_atomic_cmp_set(mtx->lock, old, val)) {
+ break;
+ }
+ }
+
+#if (NGX_HAVE_POSIX_SEM)
+ {
+
+ if (wait == 0 || !mtx->semaphore) {
+ return;
+ }
+
+ ngx_log_debug1(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0,
+ "shmtx wake %XA", old);
+
+ if (sem_post(&mtx->sem) == -1) {
+ ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, ngx_errno,
+ "sem_post() failed while wake shmtx");
+ }
+ }
+#endif
+}
+
+
#else


@@ -65,4 +216,62 @@
}


+ngx_uint_t
+ngx_shmtx_trylock(ngx_shmtx_t *mtx)
+{
+ ngx_err_t err;
+
+ err = ngx_trylock_fd(mtx->fd);
+
+ if (err == 0) {
+ return 1;
+ }
+
+ if (err == NGX_EAGAIN) {
+ return 0;
+ }
+
+#if __osf__ /* Tru64 UNIX */
+
+ if (err == NGX_EACCESS) {
+ return 0;
+ }
+
#endif
+
+ ngx_log_abort(err, ngx_trylock_fd_n " %s failed", mtx->name);
+
+ return 0;
+}
+
+
+void
+ngx_shmtx_lock(ngx_shmtx_t *mtx)
+{
+ ngx_err_t err;
+
+ err = ngx_lock_fd(mtx->fd);
+
+ if (err == 0) {
+ return;
+ }
+
+ ngx_log_abort(err, ngx_lock_fd_n " %s failed", mtx->name);
+}
+
+
+void
+ngx_shmtx_unlock(ngx_shmtx_t *mtx)
+{
+ ngx_err_t err;
+
+ err = ngx_unlock_fd(mtx->fd);
+
+ if (err == 0) {
+ return;
+ }
+
+ ngx_log_abort(err, ngx_unlock_fd_n " %s failed", mtx->name);
+}
+
+#endif
Index: src/core/ngx_shmtx.h
===================================================================
--- src/core/ngx_shmtx.h (revision 3907)
+++ src/core/ngx_shmtx.h (working copy)
@@ -15,95 +15,23 @@
typedef struct {
#if (NGX_HAVE_ATOMIC_OPS)
ngx_atomic_t *lock;
+#if (NGX_HAVE_POSIX_SEM)
+ ngx_uint_t semaphore;
+ sem_t sem;
+#endif
#else
ngx_fd_t fd;
u_char *name;
#endif
+ ngx_uint_t spin;
} ngx_shmtx_t;


ngx_int_t ngx_shmtx_create(ngx_shmtx_t *mtx, void *addr, u_char *name);
-
-
-#if (NGX_HAVE_ATOMIC_OPS)
-
-static ngx_inline ngx_uint_t
-ngx_shmtx_trylock(ngx_shmtx_t *mtx)
-{
- return (*mtx->lock == 0 && ngx_atomic_cmp_set(mtx->lock, 0, ngx_pid));
-}
-
-#define ngx_shmtx_lock(mtx) ngx_spinlock((mtx)->lock, ngx_pid, 1024)
-
-#define ngx_shmtx_unlock(mtx) (void) ngx_atomic_cmp_set((mtx)->lock, ngx_pid, 0)
-
-#define ngx_shmtx_destory(mtx)
-
-
-#else
-
-static ngx_inline ngx_uint_t
-ngx_shmtx_trylock(ngx_shmtx_t *mtx)
-{
- ngx_err_t err;
-
- err = ngx_trylock_fd(mtx->fd);
-
- if (err == 0) {
- return 1;
- }
-
- if (err == NGX_EAGAIN) {
- return 0;
- }
-
-#if __osf__ /* Tru64 UNIX */
-
- if (err == NGX_EACCESS) {
- return 0;
- }
-
-#endif
-
- ngx_log_abort(err, ngx_trylock_fd_n " %s failed", mtx->name);
-
- return 0;
-}
-
-
-static ngx_inline void
-ngx_shmtx_lock(ngx_shmtx_t *mtx)
-{
- ngx_err_t err;
-
- err = ngx_lock_fd(mtx->fd);
-
- if (err == 0) {
- return;
- }
-
- ngx_log_abort(err, ngx_lock_fd_n " %s failed", mtx->name);
-}
-
-
-static ngx_inline void
-ngx_shmtx_unlock(ngx_shmtx_t *mtx)
-{
- ngx_err_t err;
-
- err = ngx_unlock_fd(mtx->fd);
-
- if (err == 0) {
- return;
- }
-
- ngx_log_abort(err, ngx_unlock_fd_n " %s failed", mtx->name);
-}
-
-
void ngx_shmtx_destory(ngx_shmtx_t *mtx);
+ngx_uint_t ngx_shmtx_trylock(ngx_shmtx_t *mtx);
+void ngx_shmtx_lock(ngx_shmtx_t *mtx);
+void ngx_shmtx_unlock(ngx_shmtx_t *mtx);

-#endif

-
#endif /* _NGX_SHMTX_H_INCLUDED_ */
Index: auto/os/freebsd
===================================================================
--- auto/os/freebsd (revision 3907)
+++ auto/os/freebsd (working copy)
@@ -49,7 +49,16 @@
have=NGX_HAVE_AIO_SENDFILE . auto/have
fi

+# POSIX semaphores
+# http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/127545

+if [ $osreldate -ge 701106 ]; then
+ echo " + POSIX semaphores should work"
+else
+ have=NGX_HAVE_POSIX_SEM . auto/nohave
+fi
+
+
# kqueue

if [ \( $osreldate -lt 500000 -a $osreldate -ge 410000 \) \
Index: auto/unix
===================================================================
--- auto/unix (revision 3907)
+++ auto/unix (working copy)
@@ -234,6 +234,18 @@
. auto/feature


+ngx_feature="POSIX semaphores"
+ngx_feature_name="NGX_HAVE_POSIX_SEM"
+ngx_feature_run=yes
+ngx_feature_incs="#include <semaphore.h>"
+ngx_feature_path=
+ngx_feature_libs=
+ngx_feature_test="sem_t sem;
+ if (sem_init(&sem, 1, 0) == -1) return 1;
+ sem_destroy(&sem);"
+. auto/feature
+
+
ngx_feature="struct msghdr.msg_control"
ngx_feature_name="NGX_HAVE_MSGHDR_MSG_CONTROL"
ngx_feature_run=no
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Subject Author Posted

posix semaphores patch

Igor Sysoev May 04, 2011 06:50AM



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