Use spinlock for futures when possible.faster-futures

5 files changed, 156 insertions, 54 deletions

diff --git a/libdimension/bench/future.c b/libdimension/bench/future.c
index 5937c3c..3a9de4a 100644
--- a/libdimension/bench/future.c
+++ b/libdimension/bench/future.c
@@ -53,9 +53,9 @@ dmnsn_bench_thread(void *ptr)
   printf("dmnsn_future_increment(): %ld\n", sandglass.grains);
 
   /* Reset the progress. */
-  dmnsn_lock_mutex(&future->mutex);
+  dmnsn_lock_future(future);
     future->progress = 0;
-  dmnsn_unlock_mutex(&future->mutex);
+  dmnsn_unlock_future(future);
 
   /* Now run a bunch of increments concurrently. */
   return dmnsn_execute_concurrently(&dmnsn_bench_future, future, nthreads);
diff --git a/libdimension/future-impl.h b/libdimension/future-impl.h
index 4ec6f75..c8e5d63 100644
--- a/libdimension/future-impl.h
+++ b/libdimension/future-impl.h
@@ -42,6 +42,11 @@ struct dmnsn_future {
   /** The worker thread. */
   pthread_t thread;
 
+#if DMNSN_SPINLOCK
+  /** If spinlocks are supported, use them instead of mutexes. */
+  pthread_spinlock_t spinlock;
+#endif
+
   /** Mutex to guard progress and total. */
   pthread_mutex_t mutex;
 
diff --git a/libdimension/future.c b/libdimension/future.c
index 6ea15ae..555330f 100644
--- a/libdimension/future.c
+++ b/libdimension/future.c
@@ -41,6 +41,9 @@ dmnsn_new_future(void)
   future->progress = 0;
   future->total    = 1;
 
+#if DMNSN_SPINLOCK
+  dmnsn_initialize_spinlock(&future->spinlock, PTHREAD_PROCESS_PRIVATE);
+#endif
   dmnsn_initialize_mutex(&future->mutex);
   dmnsn_initialize_cond(&future->cond);
 
@@ -67,6 +70,9 @@ dmnsn_future_join(dmnsn_future *future)
     /* Free the future object */
     dmnsn_destroy_cond(&future->cond);
     dmnsn_destroy_mutex(&future->mutex);
+#if DMNSN_SPINLOCK
+    dmnsn_destroy_spinlock(&future->spinlock);
+#endif
     dmnsn_free(future);
   }
 
@@ -80,11 +86,49 @@ dmnsn_future_cancel(dmnsn_future *future)
   pthread_cancel(future->thread);
 }
 
-/**
- * Get the current progress, without locking anything.
- *
- * future->mutex must be locked for this call to be safe.
- */
+/** Lock the appropriate lock for a future. */
+static inline void
+dmnsn_lock_future(const dmnsn_future *future)
+{
+#if DMNSN_SPINLOCK
+  dmnsn_lock_spinlock(&MUTATE(future)->spinlock);
+#else
+  dmnsn_lock_mutex(&MUTATE(future)->mutex);
+#endif
+}
+
+/** Unlock the appropriate lock for a future. */
+static inline void
+dmnsn_unlock_future(const dmnsn_future *future)
+{
+#if DMNSN_SPINLOCK
+  dmnsn_unlock_spinlock(&MUTATE(future)->spinlock);
+#else
+  dmnsn_unlock_mutex(&MUTATE(future)->mutex);
+#endif
+}
+
+/** Lock the future's mutex specifically, if we have the spinlock already. */
+static inline void
+dmnsn_future_exchange_lock(const dmnsn_future *future)
+{
+#if DMNSN_SPINLOCK
+  dmnsn_unlock_spinlock(&MUTATE(future)->spinlock);
+  dmnsn_lock_mutex(&MUTATE(future)->mutex);
+#endif
+}
+
+/** Unlock the future's mutex specifically, if we have the spinlock already. */
+static inline void
+dmnsn_future_exchange_unlock(const dmnsn_future *future)
+{
+#if DMNSN_SPINLOCK
+  dmnsn_unlock_mutex(&MUTATE(future)->mutex);
+  dmnsn_lock_spinlock(&MUTATE(future)->spinlock);
+#endif
+}
+
+/** Get the current progress, without locking anything. */
 static inline double
 dmnsn_future_progress_unlocked(const dmnsn_future *future)
 {
@@ -95,12 +139,11 @@ dmnsn_future_progress_unlocked(const dmnsn_future *future)
 double
 dmnsn_future_progress(const dmnsn_future *future)
 {
-  dmnsn_future *mfuture = MUTATE(future);
   double progress;
 
-  dmnsn_lock_mutex(&mfuture->mutex);
-    progress = dmnsn_future_progress_unlocked(mfuture);
-  dmnsn_unlock_mutex(&mfuture->mutex);
+  dmnsn_lock_future(future);
+    progress = dmnsn_future_progress_unlocked(future);
+  dmnsn_unlock_future(future);
 
   return progress;
 }
@@ -111,24 +154,26 @@ dmnsn_future_wait(const dmnsn_future *future, double progress)
 {
   dmnsn_future *mfuture = MUTATE(future);
 
-  dmnsn_lock_mutex(&mfuture->mutex);
+  dmnsn_lock_future(mfuture);
     while (dmnsn_future_progress_unlocked(mfuture) < progress) {
       /* Set the minimum waited-on value */
       if (progress < mfuture->min_wait)
         mfuture->min_wait = progress;
 
-      dmnsn_cond_wait(&mfuture->cond, &mfuture->mutex);
+      dmnsn_future_exchange_lock(mfuture);
+        dmnsn_cond_wait(&mfuture->cond, &mfuture->mutex);
+      dmnsn_future_exchange_unlock(mfuture);
     }
-  dmnsn_unlock_mutex(&mfuture->mutex);
+  dmnsn_unlock_future(mfuture);
 }
 
 /* Set the total number of loop iterations */
 void
 dmnsn_future_set_total(dmnsn_future *future, size_t total)
 {
-  dmnsn_lock_mutex(&future->mutex);
+  dmnsn_lock_future(future);
     future->total = total;
-  dmnsn_unlock_mutex(&future->mutex);
+  dmnsn_unlock_future(future);
 }
 
 /* Increment the number of completed loop iterations */
@@ -140,22 +185,26 @@ dmnsn_future_increment(dmnsn_future *future)
      on cancellation */
   pthread_testcancel();
 
-  dmnsn_lock_mutex(&future->mutex);
+  dmnsn_lock_future(future);
     ++future->progress;
 
     if (dmnsn_future_progress_unlocked(future) >= future->min_wait) {
       future->min_wait = 1.0;
-      dmnsn_cond_broadcast(&future->cond);
+      dmnsn_future_exchange_lock(future);
+        dmnsn_cond_broadcast(&future->cond);
+      dmnsn_future_exchange_unlock(future);
     }
-  dmnsn_unlock_mutex(&future->mutex);
+  dmnsn_unlock_future(future);
 }
 
 /* Immediately set to 100% completion */
 void
 dmnsn_future_done(dmnsn_future *future)
 {
-  dmnsn_lock_mutex(&future->mutex);
+  dmnsn_lock_future(future);
     future->progress = future->total;
-    dmnsn_cond_broadcast(&future->cond);
-  dmnsn_unlock_mutex(&future->mutex);
+    dmnsn_future_exchange_lock(future);
+      dmnsn_cond_broadcast(&future->cond);
+    dmnsn_future_exchange_unlock(future);
+  dmnsn_unlock_future(future);
 }
diff --git a/libdimension/threads.c b/libdimension/threads.c
index 0aed16d..9749976 100644
--- a/libdimension/threads.c
+++ b/libdimension/threads.c
@@ -1,5 +1,5 @@
 /*************************************************************************
- * Copyright (C) 2010-2011 Tavian Barnes <tavianator@tavianator.com>     *
+ * Copyright (C) 2010-2013 Tavian Barnes <tavianator@tavianator.com>     *
  *                                                                       *
  * This file is part of The Dimension Library.                           *
  *                                                                       *
@@ -169,7 +169,7 @@ dmnsn_initialize_mutex(pthread_mutex_t *mutex)
 }
 
 void
-dmnsn_lock_mutex_impl(pthread_mutex_t *mutex)
+dmnsn_lock_mutex(pthread_mutex_t *mutex)
 {
   if (pthread_mutex_lock(mutex) != 0) {
     dmnsn_error("Couldn't lock mutex.");
@@ -177,7 +177,7 @@ dmnsn_lock_mutex_impl(pthread_mutex_t *mutex)
 }
 
 void
-dmnsn_unlock_mutex_impl(pthread_mutex_t *mutex)
+dmnsn_unlock_mutex(pthread_mutex_t *mutex)
 {
   if (pthread_mutex_unlock(mutex) != 0) {
     dmnsn_error("Couldn't unlock mutex.");
@@ -201,7 +201,7 @@ dmnsn_initialize_rwlock(pthread_rwlock_t *rwlock)
 }
 
 void
-dmnsn_read_lock_impl(pthread_rwlock_t *rwlock)
+dmnsn_read_lock(pthread_rwlock_t *rwlock)
 {
   if (pthread_rwlock_rdlock(rwlock) != 0) {
     dmnsn_error("Couldn't acquire read lock.");
@@ -209,7 +209,7 @@ dmnsn_read_lock_impl(pthread_rwlock_t *rwlock)
 }
 
 void
-dmnsn_write_lock_impl(pthread_rwlock_t *rwlock)
+dmnsn_write_lock(pthread_rwlock_t *rwlock)
 {
   if (pthread_rwlock_wrlock(rwlock) != 0) {
     dmnsn_error("Couldn't acquire write lock.");
@@ -217,7 +217,7 @@ dmnsn_write_lock_impl(pthread_rwlock_t *rwlock)
 }
 
 void
-dmnsn_unlock_rwlock_impl(pthread_rwlock_t *rwlock)
+dmnsn_unlock_rwlock(pthread_rwlock_t *rwlock)
 {
   if (pthread_rwlock_unlock(rwlock) != 0) {
     dmnsn_error("Couldn't unlock read-write lock.");
@@ -232,6 +232,42 @@ dmnsn_destroy_rwlock(pthread_rwlock_t *rwlock)
   }
 }
 
+#if DMNSN_SPINLOCK
+
+void
+dmnsn_initialize_spinlock(pthread_spinlock_t *lock, int pshared)
+{
+  if (pthread_spin_init(lock, pshared) != 0) {
+    dmnsn_error("Couldn't initialize spinlock.");
+  }
+}
+
+void
+dmnsn_lock_spinlock(pthread_spinlock_t *lock)
+{
+  if (pthread_spin_lock(lock) != 0) {
+    dmnsn_error("Couldn't lock spinlock.");
+  }
+}
+
+void
+dmnsn_unlock_spinlock(pthread_spinlock_t *lock)
+{
+  if (pthread_spin_unlock(lock) != 0) {
+    dmnsn_error("Couldn't unlock spinlock.");
+  }
+}
+
+void
+dmnsn_destroy_spinlock(pthread_spinlock_t *lock)
+{
+  if (pthread_spin_destroy(lock) != 0) {
+    dmnsn_warning("Couldn't destroy spinlock.");
+  }
+}
+
+#endif /* DMNSN_SPINLOCK */
+
 void
 dmnsn_initialize_cond(pthread_cond_t *cond)
 {
diff --git a/libdimension/threads.h b/libdimension/threads.h
index ea9fb2a..7b7aae6 100644
--- a/libdimension/threads.h
+++ b/libdimension/threads.h
@@ -1,5 +1,5 @@
 /*************************************************************************
- * Copyright (C) 2010-2011 Tavian Barnes <tavianator@tavianator.com>     *
+ * Copyright (C) 2010-2013 Tavian Barnes <tavianator@tavianator.com>     *
  *                                                                       *
  * This file is part of The Dimension Library.                           *
  *                                                                       *
@@ -67,24 +67,17 @@ DMNSN_INTERNAL int dmnsn_execute_concurrently(dmnsn_ccthread_fn *ccthread_fn,
  */
 DMNSN_INTERNAL void dmnsn_initialize_mutex(pthread_mutex_t *mutex);
 
-/** dmnsn_lock_mutex() implementation. */
-DMNSN_INTERNAL void dmnsn_lock_mutex_impl(pthread_mutex_t *mutex);
-/** dmnsn_unlock_mutex() implementation. */
-DMNSN_INTERNAL void dmnsn_unlock_mutex_impl(pthread_mutex_t *mutex);
-
 /**
  * Lock a mutex, bailing out on failure.
- * Contains a {, so must be used in the same block as dmnsn_unlock_mutex().
  * @param[in,out] mutex  The mutex to lock.
  */
-#define dmnsn_lock_mutex(mutex) dmnsn_lock_mutex_impl((mutex)); {
+DMNSN_INTERNAL void dmnsn_lock_mutex(pthread_mutex_t *mutex);
 
 /**
- * Lock a mutex, bailing out on failure.
- * Contains a }, so must be used in the same block as dmnsn_lock_mutex().
+ * Unlock a mutex, bailing out on failure.
  * @param[in,out] mutex  The mutex to unlock.
  */
-#define dmnsn_unlock_mutex(mutex) dmnsn_unlock_mutex_impl((mutex)); }
+DMNSN_INTERNAL void dmnsn_unlock_mutex(pthread_mutex_t *mutex);
 
 /**
  * Destroy a mutex, warning on failure.
@@ -98,34 +91,23 @@ DMNSN_INTERNAL void dmnsn_destroy_mutex(pthread_mutex_t *mutex);
  */
 DMNSN_INTERNAL void dmnsn_initialize_rwlock(pthread_rwlock_t *rwlock);
 
-/** dmnsn_read_lock() implementation. */
-DMNSN_INTERNAL void dmnsn_read_lock_impl(pthread_rwlock_t *rwlock);
-/** dmnsn_write_lock() implementation. */
-DMNSN_INTERNAL void dmnsn_write_lock_impl(pthread_rwlock_t *rwlock);
-/** dmnsn_unlock_rwlock() implementation. */
-DMNSN_INTERNAL void dmnsn_unlock_rwlock_impl(pthread_rwlock_t *rwlock);
-
 /**
  * Lock a read-write lock, bailing out on failure.
- * Contains a {, so must be used in the same block as dmnsn_unlock_rwlock().
  * @param[in,out] rwlock  The read-write lock to lock.
  */
-#define dmnsn_read_lock(rwlock) dmnsn_read_lock_impl((rwlock)); {
+DMNSN_INTERNAL void dmnsn_read_lock(pthread_rwlock_t *rwlock);
 
 /**
  * Lock a read-write lock, bailing out on failure.
- * Contains a {, so must be used in the same block as dmnsn_unlock_rwlock().
  * @param[in,out] rwlock  The read-write lock to lock.
  */
-#define dmnsn_write_lock(rwlock) dmnsn_write_lock_impl((rwlock)); {
+DMNSN_INTERNAL void dmnsn_write_lock(pthread_rwlock_t *rwlock);
 
 /**
- * Lock a read-write lock, bailing out on failure.
- * Contains a }, so must be used in the same block as dmnsn_read_lock() or
- * dmnsn_write_lock().
+ * Unlock a read-write lock, bailing out on failure.
  * @param[in,out] rwlock  The read-write lock to lock.
  */
-#define dmnsn_unlock_rwlock(rwlock) dmnsn_unlock_rwlock_impl((rwlock)); }
+DMNSN_INTERNAL void dmnsn_unlock_rwlock(pthread_rwlock_t *rwlock);
 
 /**
  * Destroy a read-write lock, warning on failure.
@@ -133,6 +115,36 @@ DMNSN_INTERNAL void dmnsn_unlock_rwlock_impl(pthread_rwlock_t *rwlock);
  */
 DMNSN_INTERNAL void dmnsn_destroy_rwlock(pthread_rwlock_t *rwlock);
 
+#if DMNSN_SPINLOCK
+
+/**
+ * Initialize a read-write lock, bailing out on failure.
+ * @param[out] lock     The spinlock to initialize.
+ * @param[in]  pshared  The process-specific flag (PTHREAD_PROCESS_SHARED or
+ *                      PTHREAD_PROCESS_PRIVATE).
+ */
+DMNSN_INTERNAL void dmnsn_initialize_spinlock(pthread_spinlock_t *lock, int pshared);
+
+/**
+ * Lock the given spinlock, bailing out on failure.
+ * @param[in] lock  The spinlock to lock.
+ */
+DMNSN_INTERNAL void dmnsn_lock_spinlock(pthread_spinlock_t *lock);
+
+/**
+ * Unlock the given spinlock, bailing out on failure.
+ * @param[in] lock  The spinlock to unlock.
+ */
+DMNSN_INTERNAL void dmnsn_unlock_spinlock(pthread_spinlock_t *lock);
+
+/**
+ * Destroy a spinlock lock, warning on failure.
+ * @param[in,out] lock  The spinlock to destroy.
+ */
+DMNSN_INTERNAL void dmnsn_destroy_spinlock(pthread_spinlock_t *lock);
+
+#endif /* DMNSN_SPINLOCK */
+
 /**
  * Initialize a condition variable, bailing out on failure.
  * @param[out] cond  The condition variable to initialize.