use condition locks to avoid polling/spinning

git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/performance/trunk@33251 72102866-910b-0410-8b05-ffd578937521

ChangeLog

@@ -1,3 +1,10 @@
+2011-06-05 Richard Frith-Macdonald  <rfm@gnu.org>
+
+	* GSFIFO.h:
+	* GSFIFO.m:
+	Use condition locks so that, if we have locking for both addition
+	and removal, we can signal threads waiting at the other end.
+
 2011-06-03 Richard Frith-Macdonald  <rfm@gnu.org>
 
 	* GSTicker.m: Thread safety fixes ... make date storage volatile and

GSFIFO.h

@@ -24,7 +24,7 @@
    */
 #import <Foundation/NSObject.h>
 
-@class NSLock;
+@class NSConditionLock;
 @class NSString;
 
 
@@ -42,12 +42,12 @@
  * each stage.<br />
  * Where there is a single consumer thread, a fast lock-fre algorthm is
  * used to get items from the FIFO, similarly, where there is a single
- * producer thread a the addition of items to the FIFO can be lock-free.<br />
+ * producer thread the addition of items to the FIFO can be lock-free.<br />
  * To minimise the overheads of using the FIFO, we provide inline functions
  * to support the addition of items in the single producer thread case and to
  * support the removal of items in the single consumer thread case.  When
  * operting that way, the overhead of using the FIFO is only a few CPU cycles
- * and it becomes reasonable to split sequentional procesing into a long
+ * and it becomes reasonable to split sequentional processing into a long
  * series of small operations each handled by a separate thread (making
  * effective use of a multi-cpu machine).<br />
  * The FIFO may also be useful where you don't have a strictly sequential
@@ -58,7 +58,12 @@
  * and multiple consumers.  In these rarer cases, some locking is required
  * and the use of the inline functions is not allowed (you must call the
  * -get method wherever you have multiple consumer threads, and must call
- * the -put: method wherever you have multiple producer threads).
+ * the -put: method wherever you have multiple producer threads).<br />
+ * Where both multiple producers and multiple consumers are configured,
+ * there are two locks used to coordinate access to the FIFO, and the
+ * addition of an item to an empty FIFO or removal of an item from a full
+ * FIFO signals any blocked threads to cmplete their access to the FIFO
+ * immediately.
  */
 @interface	GSFIFO : NSObject
 {
@@ -69,16 +74,16 @@
  */
   volatile uint64_t	_head;
   volatile uint64_t	_tail;
-  void		**_items;
-  uint32_t	_capacity;
+  void			**_items;
+  uint32_t		_capacity;
 @private
-  uint16_t	granularity;
-  uint16_t	timeout;
-  uint64_t	fullCount;
-  uint64_t	emptyCount;
-  NSLock	*getLock;
-  NSLock	*putLock;
-  NSString	*name;
+  uint16_t		granularity;
+  uint16_t		timeout;
+  uint64_t		fullCount;
+  uint64_t		emptyCount;
+  NSConditionLock	*getLock;
+  NSConditionLock	*putLock;
+  NSString		*name;
 }
 
 /** Returns the approximate number of items in the FIFO.
@@ -103,7 +108,12 @@
  * method) by using of locking while adding items to the FIFO.<br />
  * If the multiConsumer flag is YES, the FIFO is configured to support
  * multiple consumer threads (ie more than one thread using the -get
- * method) by using of locking while removng items from the FIFO.<br />
+ * method) by using of locking while removing items from the FIFO.<br />
+ * If both multiConsumer and multiProducer are set, cooperative use of
+ * locking by put and get methods means that no retries are required
+ * and the granularity is ignored (a -put: to an empty FIFO allows any
+ * blocked -get to proceed, and a -get from a full FIFO allows any
+ * blocked -put: to proceed immediately).<br />
  * The name string is simply used to identify the receiver when printing
  * diagnostics.
  */

GSFIFO.m

@@ -29,6 +29,105 @@
 
 @implementation	GSFIFO
 
+- (void*) _cooperatingGetShouldBlock: (BOOL)block
+{
+  void	*item;
+  BOOL	wasFull = NO;
+  BOOL	isEmpty = NO;
+
+  if (NO == block)
+    {
+      if (NO == [getLock tryLockWhenCondition: 1])
+	{
+	  return 0;
+	}
+    }
+  else if (0 == timeout)
+    {
+      [getLock lockWhenCondition: 1];
+    }
+  else
+    {
+      NSDate	*d;
+
+      d = [[NSDate alloc] initWithTimeIntervalSinceNow: 1000.0 * timeout];
+      if (NO == [getLock lockWhenCondition: 1 beforeDate: d])
+	{
+	  [d release];
+	  [NSException raise: NSGenericException
+		      format: @"Timeout waiting for new data in FIFO"];
+	}
+      [d release];
+    }
+
+  if (_head - _tail == _capacity)
+    {
+      wasFull = YES;
+    }
+  item = _items[_tail % _capacity];
+  _tail++;
+  if (_head - _tail == 0)
+    {
+      isEmpty = YES;
+    }
+  if (YES == wasFull)
+    {
+      [putLock lock];
+      [putLock unlockWithCondition: 1];
+    }
+  [getLock unlockWithCondition: isEmpty ? 0 : 1];
+  return item;
+}
+
+- (BOOL) _cooperatingPut: (void*)item shouldBlock: (BOOL)block
+{
+  BOOL	wasEmpty = NO;
+  BOOL	isFull = NO;
+
+  if (NO == block)
+    {
+      if (NO == [putLock tryLockWhenCondition: 1])
+	{
+	  return NO;
+	}
+    }
+  else if (0 == timeout)
+    {
+      [putLock lockWhenCondition: 1];
+    }
+  else
+    {
+      NSDate	*d;
+
+      d = [[NSDate alloc] initWithTimeIntervalSinceNow: 1000.0 * timeout];
+      if (NO == [putLock lockWhenCondition: 1 beforeDate: d])
+	{
+	  [d release];
+	  [NSException raise: NSGenericException
+		      format: @"Timeout waiting for space in FIFO"];
+	}
+      [d release];
+    }
+
+  if (_head - _tail == 0)
+    {
+      wasEmpty = YES;
+    }
+  _items[_head % _capacity] = item;
+  _head++;
+  if (_head - _tail == _capacity)
+    {
+      isFull = YES;
+    }
+  if (YES == wasEmpty)
+    {
+      [getLock lock];
+      [getLock unlockWithCondition: 1];
+    }
+  [putLock unlockWithCondition: isFull ? 0 : 1];
+  return YES;
+}
+
 - (void) dealloc
 {
   [name release];
@@ -74,6 +173,10 @@
 	}
       emptyCount++;
     }
+  else if (nil != putLock)
+    {
+      return [self _cooperatingGetShouldBlock: YES];
+    }
   else
     {
       [getLock lock];
@@ -99,7 +202,7 @@
 	{
 	  [getLock unlock];
 	  [NSException raise: NSGenericException
-		      format: @"Timout waiting for new data in FIFO"];
+		      format: @"Timeout waiting for new data in FIFO"];
 	}
       tmp = fib + old;
       old = fib;
@@ -134,8 +237,8 @@
   granularity = g;
   timeout = t;
   _items = (void*)NSZoneMalloc(NSDefaultMallocZone(), sizeof(void*) * c);
-  if (YES == mp) putLock = [NSLock new];
-  if (YES == mc) getLock = [NSLock new];
+  if (YES == mp) putLock = [[NSConditionLock alloc] initWithCondition: 1];
+  if (YES == mc) getLock = [[NSConditionLock alloc] initWithCondition: 0];
   name = [n copy];
   return self;
 }
@@ -156,6 +259,10 @@
 	}
       fullCount++;
     }
+  else if (nil != getLock)
+    {
+      [self _cooperatingPut: item shouldBlock: YES];
+    }
   else
     {
       [putLock lock];
@@ -181,7 +288,7 @@
 	{
 	  [putLock unlock];
 	  [NSException raise: NSGenericException
-		      format: @"Timout waiting for space in FIFO"];
+		      format: @"Timeout waiting for space in FIFO"];
 	}
       tmp = fib + old;
       old = fib;
@@ -213,6 +320,10 @@
 	}
       emptyCount++;
     }
+  else if (nil != putLock)
+    {
+      return [self _cooperatingGetShouldBlock: NO];
+    }
   else
     {
       [getLock lock];
@@ -241,6 +352,10 @@
 	}
       fullCount++;
     }
+  else if (nil != getLock)
+    {
+      return [self _cooperatingPut: item shouldBlock: NO];
+    }
   else
     {
       [putLock lock];