Multi-thread GEMM Performance Improvement on NeoverseV1 (DIVIDE_RATE=1)

driver/level3/gemm.c

@@ -63,6 +63,10 @@
 #define DIVIDE_RATE GEMM_DIVIDE_RATE
 #endif
 
+#ifdef GEMM_DIVIDE_LIMIT
+#define DIVIDE_LIMIT GEMM_DIVIDE_LIMIT
+#endif
+
 #ifdef THREADED_LEVEL3
 #include "level3_thread.c"
 #else

driver/level3/level3_thread.c

@@ -246,6 +246,7 @@ static int inner_thread(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n,
 
   BLASLONG nthreads_m;
   BLASLONG mypos_m, mypos_n;
+  BLASLONG divide_rate = DIVIDE_RATE;
 
   BLASLONG is, js, ls, bufferside, jjs;
   BLASLONG min_i, min_l, div_n, min_jj;
@@ -280,6 +281,11 @@ static int inner_thread(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n,
   alpha = (FLOAT *)args -> alpha;
   beta  = (FLOAT *)args -> beta;
 
+  /* Disable divide_rate when N of all threads are less than to DIVIDE_LIMIT */
+#ifdef DIVIDE_LIMIT
+  if (N < DIVIDE_LIMIT) divide_rate = 1;
+#endif
+
   /* Initialize 2D CPU distribution */
   nthreads_m = args -> nthreads;
   if (range_m) {
@@ -321,9 +327,9 @@ static int inner_thread(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n,
       ) return 0;
 
   /* Initialize workspace for local region of B */
-  div_n = (n_to - n_from + DIVIDE_RATE - 1) / DIVIDE_RATE;
+  div_n = (n_to - n_from + divide_rate - 1) / divide_rate;
   buffer[0] = sb;
-  for (i = 1; i < DIVIDE_RATE; i++) {
+  for (i = 1; i < divide_rate; i++) {
     buffer[i] = buffer[i - 1] + GEMM_Q * ((div_n + GEMM_UNROLL_N - 1)/GEMM_UNROLL_N) * GEMM_UNROLL_N * COMPSIZE;
   }
 
@@ -365,7 +371,7 @@ static int inner_thread(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n,
     STOP_RPCC(copy_A);
 
     /* Copy local region of B into workspace and apply kernel */
-    div_n = (n_to - n_from + DIVIDE_RATE - 1) / DIVIDE_RATE;
+    div_n = (n_to - n_from + divide_rate - 1) / divide_rate;
     for (js = n_from, bufferside = 0; js < n_to; js += div_n, bufferside ++) {
 
       /* Make sure if no one is using workspace */
@@ -434,7 +440,7 @@ static int inner_thread(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n,
       if (current >= (mypos_n + 1) * nthreads_m) current = mypos_n * nthreads_m;
 
       /* Split other region of B into parts */
-      div_n = (range_n[current + 1]  - range_n[current] + DIVIDE_RATE - 1) / DIVIDE_RATE;
+      div_n = (range_n[current + 1]  - range_n[current] + divide_rate - 1) / divide_rate;
       for (js = range_n[current], bufferside = 0; js < range_n[current + 1]; js += div_n, bufferside ++) {
         if (current != mypos) {
 
@@ -485,7 +491,7 @@ static int inner_thread(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n,
       do {
 
         /* Split region of B into parts and apply kernel */
-	div_n = (range_n[current + 1]  - range_n[current] + DIVIDE_RATE - 1) / DIVIDE_RATE;
+	div_n = (range_n[current + 1]  - range_n[current] + divide_rate - 1) / divide_rate;
 	for (js = range_n[current], bufferside = 0; js < range_n[current + 1]; js += div_n, bufferside ++) {
 
           /* Apply kernel with local region of A and part of region of B */
@@ -520,7 +526,7 @@ static int inner_thread(blas_arg_t *args, BLASLONG *range_m, BLASLONG *range_n,
   /* Wait until all other threads are done with local region of B */
   START_RPCC();
   for (i = 0; i < args -> nthreads; i++) {
-    for (js = 0; js < DIVIDE_RATE; js++) {
+    for (js = 0; js < divide_rate; js++) {
       while (job[mypos].working[i][CACHE_LINE_SIZE * js] ) {YIELDING;};
     }
   }

param.h

@@ -3585,6 +3585,8 @@ is a big desktop or server with abundant cache rather than a phone or embedded d
 
 #elif defined(NEOVERSEV1) // 256-bit SVE
 
+#define GEMM_DIVIDE_LIMIT       3
+
 #if defined(XDOUBLE) || defined(DOUBLE)
 #define SWITCH_RATIO            8
 #define GEMM_PREFERED_SIZE      4