Revert "Improve Windows threading performance scaling"

Author: martin-frbg

CONTRIBUTORS.md

@@ -216,8 +216,3 @@ In chronological order:
 
 * Pablo Romero <https://github.com/pablorcum>
   * [2022-08] Fix building from sources for QNX
-
-* Mark Seminatore <https://github.com/mseminatore>
-  * [2023-06-23] Fix bounds issue in goto_set_num_threads
-  * [2023-06-23] Improve Windows threading performance scaling
-  

driver/others/blas_server_win32.c

@@ -50,19 +50,11 @@
 
 /* This is a thread implementation for Win32 lazy implementation */
 
-#if defined (__GNUC__) && (__GNUC__ < 6)
-	#define WIN_CAS(dest, exch, comp) __sync_val_compare_and_swap(dest, comp, exch)
-#else
-	#if defined(_WIN64)
-		#define WIN_CAS(dest, exch, comp) InterlockedCompareExchange64(dest, exch, comp)
-	#else
-		#define WIN_CAS(dest, exch, comp) InterlockedCompareExchange(dest, exch, comp)
-	#endif
-#endif
-
 /* Thread server common information */
 typedef struct{
-  HANDLE taskSemaphore;
+  CRITICAL_SECTION lock;
+  HANDLE filled;
+  HANDLE killed;
 
   blas_queue_t	*queue;    /* Parameter Pointer */
   int		shutdown;  /* server shutdown flag */
@@ -79,6 +71,8 @@ static blas_pool_t   pool;
 static HANDLE	    blas_threads   [MAX_CPU_NUMBER];
 static DWORD	    blas_threads_id[MAX_CPU_NUMBER];
 
+
+
 static void legacy_exec(void *func, int mode, blas_arg_t *args, void *sb){
 
       if (!(mode & BLAS_COMPLEX)){
@@ -204,6 +198,7 @@ static void legacy_exec(void *func, int mode, blas_arg_t *args, void *sb){
 
 /* This is a main routine of threads. Each thread waits until job is */
 /* queued.                                                           */
+
 static DWORD WINAPI blas_thread_server(void *arg){
 
   /* Thread identifier */
@@ -212,7 +207,9 @@ static DWORD WINAPI blas_thread_server(void *arg){
 #endif
 
   void *buffer, *sa, *sb;
-  volatile blas_queue_t	*queue;
+  blas_queue_t	*queue;
+  DWORD action;
+  HANDLE handles[] = {pool.filled, pool.killed};
 
   /* Each server needs each buffer */
   buffer   = blas_memory_alloc(2);
@@ -229,32 +226,28 @@ static DWORD WINAPI blas_thread_server(void *arg){
     fprintf(STDERR, "Server[%2ld] Waiting for Queue.\n", cpu);
 #endif
 
-	// all worker threads wait on the semaphore
-	WaitForSingleObject(pool.taskSemaphore, INFINITE);
+    do {
+      action = WaitForMultipleObjects(2, handles, FALSE, INFINITE);
+    } while ((action != WAIT_OBJECT_0) && (action != WAIT_OBJECT_0 + 1));
+
+    if (action == WAIT_OBJECT_0 + 1) break;
 
-	// kill the thread if we are shutting down the server
-	if (pool.shutdown)
-		break;
-    
 #ifdef SMP_DEBUG
     fprintf(STDERR, "Server[%2ld] Got it.\n", cpu);
 #endif
 
-	// grab a queued task and update the list
-	volatile blas_queue_t* queue_next;
-	INT_PTR prev_value;
-	do {
-		queue = (volatile blas_queue_t*)pool.queue;
-		if (!queue)
-			break;
+    EnterCriticalSection(&pool.lock);
+
+    queue = pool.queue;
+    if (queue) pool.queue = queue->next;
 
-		queue_next = (volatile blas_queue_t*)queue->next;
-		prev_value = WIN_CAS((INT_PTR*)&pool.queue, (INT_PTR)queue_next, (INT_PTR)queue);
-	} while (prev_value != queue);
+    LeaveCriticalSection(&pool.lock);
 
     if (queue)  {
       int (*routine)(blas_arg_t *, void *, void *, void *, void *, BLASLONG) = queue -> routine;
 
+      if (pool.queue) SetEvent(pool.filled);
+
       sa = queue -> sa;
       sb = queue -> sb;
 
@@ -339,8 +332,13 @@ static DWORD WINAPI blas_thread_server(void *arg){
     fprintf(STDERR, "Server[%2ld] Finished!\n", cpu);
 #endif
 
-	// mark our sub-task as complete
-	InterlockedDecrement(&queue->status);
+    EnterCriticalSection(&queue->lock);
+
+    queue -> status = BLAS_STATUS_FINISHED;
+
+    LeaveCriticalSection(&queue->lock);
+
+    SetEvent(queue->finish);
   }
 
   /* Shutdown procedure */
@@ -355,7 +353,7 @@ static DWORD WINAPI blas_thread_server(void *arg){
   }
 
 /* Initializing routine */
-  int blas_thread_init(void){
+int blas_thread_init(void){
   BLASLONG i;
 
   if (blas_server_avail || (blas_cpu_number <= 1)) return 0;
@@ -369,7 +367,9 @@ static DWORD WINAPI blas_thread_server(void *arg){
 
   if (!blas_server_avail){
 
-	pool.taskSemaphore = CreateSemaphore(NULL, 0, blas_cpu_number - 1, NULL);
+    InitializeCriticalSection(&pool.lock);
+    pool.filled = CreateEvent(NULL, FALSE, FALSE, NULL);
+    pool.killed = CreateEvent(NULL, TRUE,  FALSE, NULL);
 
     pool.shutdown = 0;
     pool.queue    = NULL;
@@ -391,10 +391,11 @@ static DWORD WINAPI blas_thread_server(void *arg){
 /*
    User can call one of two routines.
 
-	 exec_blas_async ... immediately returns after jobs are queued.
+     exec_blas_async ... immediately returns after jobs are queued.
 
-	 exec_blas       ... returns after jobs are finished.
+     exec_blas       ... returns after jobs are finished.
 */
+
 int exec_blas_async(BLASLONG pos, blas_queue_t *queue){
 
 #if defined(SMP_SERVER)
@@ -408,7 +409,8 @@ int exec_blas_async(BLASLONG pos, blas_queue_t *queue){
   current = queue;
 
   while (current) {
-	current->status = 1;
+    InitializeCriticalSection(&current -> lock);
+    current -> finish = CreateEvent(NULL, FALSE, FALSE, NULL);
     current -> position = pos;
 
 #ifdef CONSISTENT_FPCSR
@@ -420,10 +422,19 @@ int exec_blas_async(BLASLONG pos, blas_queue_t *queue){
     pos ++;
   }
 
-  pool.queue = queue;
+  EnterCriticalSection(&pool.lock);
+
+  if (pool.queue) {
+    current = pool.queue;
+    while (current -> next) current = current -> next;
+    current -> next = queue;
+  } else {
+    pool.queue = queue;
+  }
+
+  LeaveCriticalSection(&pool.lock);
 
-  // start up worker threads
-  ReleaseSemaphore(pool.taskSemaphore, pos - 1, NULL);
+  SetEvent(pool.filled);
 
   return 0;
 }
@@ -439,9 +450,10 @@ int exec_blas_async_wait(BLASLONG num, blas_queue_t *queue){
     fprintf(STDERR, "Waiting Queue ..\n");
 #endif
 
-	// spin-wait on each sub-task to finish
-	while (*((volatile int*)&queue->status))
-		YIELDING;
+      WaitForSingleObject(queue->finish, INFINITE);
+
+      CloseHandle(queue->finish);
+      DeleteCriticalSection(&queue -> lock);
 
       queue = queue -> next;
       num --;
@@ -489,21 +501,18 @@ int exec_blas(BLASLONG num, blas_queue_t *queue){
 
 /* Shutdown procedure, but user don't have to call this routine. The */
 /* kernel automatically kill threads.                                */
+
 int BLASFUNC(blas_thread_shutdown)(void){
 
   int i;
 
-#ifdef SMP_DEBUG
-  fprintf(STDERR, "blas_thread_shutdown..\n");
-#endif
-
   if (!blas_server_avail) return 0;
 
   LOCK_COMMAND(&server_lock);
 
   if (blas_server_avail){
 
-	  pool.shutdown = 1;
+    SetEvent(pool.killed);
 
     for(i = 0; i < blas_num_threads - 1; i++){
       // Could also just use WaitForMultipleObjects
@@ -519,7 +528,8 @@ int BLASFUNC(blas_thread_shutdown)(void){
       CloseHandle(blas_threads[i]);
     }
 
-	CloseHandle(pool.taskSemaphore);
+    CloseHandle(pool.filled);
+    CloseHandle(pool.killed);
 
     blas_server_avail = 0;
   }
@@ -549,14 +559,16 @@ void goto_set_num_threads(int num_threads)
 		//increased_threads = 1;
 	    if (!blas_server_avail){
 
-			pool.taskSemaphore = CreateSemaphore(NULL, 0, blas_cpu_number - 1, NULL);
+			InitializeCriticalSection(&pool.lock);
+			pool.filled = CreateEvent(NULL, FALSE, FALSE, NULL);
+			pool.killed = CreateEvent(NULL, TRUE,  FALSE, NULL);
 
 			pool.shutdown = 0;
 			pool.queue    = NULL;
 			blas_server_avail = 1;
 		}
 
-		for(i = blas_num_threads; i < num_threads - 1; i++){
+		for(i = blas_num_threads - 1; i < num_threads - 1; i++){
 
 			blas_threads[i] = CreateThread(NULL, 0,
 				     blas_thread_server, (void *)i,