Permit fd_tickcount stutter

Support slow clocks, such as Arm cntvct_el0, by allowing back to
back fd_tickcount() calls to return the same value.

Author: riptl

src/util/clock/fd_clock.c

@@ -355,11 +355,11 @@ fd_clock_joint_read( fd_clock_func_t clock_x, void const * args_x,
   x[ FD_CLOCK_JOINT_READ_CNT ] = clock_x( args_x );
 
   ulong best_idx = 0UL;
-  long  best_dx  = x[1] - x[0]; if( FD_UNLIKELY( best_dx<=0L ) ) return FD_CLOCK_ERR_X;
+  long  best_dx  = x[1] - x[0]; if( FD_UNLIKELY( best_dx<0L ) ) return FD_CLOCK_ERR_X;
 
   for( ulong idx=1UL; idx<FD_CLOCK_JOINT_READ_CNT; idx++ ) {
-    long dy  = y[ idx ] - y[ idx-1UL ]; if( FD_UNLIKELY( dy<=0L ) ) return FD_CLOCK_ERR_Y;
-    long dx  = x[ idx+1UL ] - x[ idx ]; if( FD_UNLIKELY( dx<=0L ) ) return FD_CLOCK_ERR_X;
+    long dy  = y[ idx ] - y[ idx-1UL ]; if( FD_UNLIKELY( dy<0L ) ) return FD_CLOCK_ERR_Y;
+    long dx  = x[ idx+1UL ] - x[ idx ]; if( FD_UNLIKELY( dx<0L ) ) return FD_CLOCK_ERR_X;
     best_idx = fd_ulong_if( best_dx<dx, best_idx, idx );
     best_dx  = fd_long_min( best_dx, dx );
   }

src/util/clock/test_clock.c

@@ -131,7 +131,7 @@ main( int     argc,
 
   init_w = (double)(init_x1-init_x0) / (double)(init_y1-init_y0);
 
-  FD_LOG_NOTICE(( "Joint read 1 (x %li ticks, y %li ns, dx %li ticks) w %e GHz", init_x1, init_y1, init_dx, init_w ));
+  FD_LOG_NOTICE(( "Joint read 1 (x %li ticks, y %li ns, dx %li ticks) w %e MHz", init_x1, init_y1, init_dx, init_w*1e3 ));
 
   FD_LOG_NOTICE(( "Creating clock" ));
 

src/util/test_util_base.c

@@ -425,7 +425,7 @@ main( int     argc,
   long tic = fd_tickcount();
   for( ulong iter=0UL; iter<1000000UL; iter++ ) {
     long toc = fd_tickcount();
-    FD_TEST( (toc - tic) > 0L );
+    FD_TEST( (toc - tic) >= 0L );
     tic = toc;
   }