Help autotuner to find more stable workload settings for -m 6900 by limiting kernel loops

src/modules/module_06900.c

@@ -40,6 +40,16 @@ u32         module_salt_type      (MAYBE_UNUSED const hashconfig_t *hashconfig,
 const char *module_st_hash        (MAYBE_UNUSED const hashconfig_t *hashconfig, MAYBE_UNUSED const user_options_t *user_options, MAYBE_UNUSED const user_options_extra_t *user_options_extra) { return ST_HASH;         }
 const char *module_st_pass        (MAYBE_UNUSED const hashconfig_t *hashconfig, MAYBE_UNUSED const user_options_t *user_options, MAYBE_UNUSED const user_options_extra_t *user_options_extra) { return ST_PASS;         }
 
+u32 module_kernel_loops_max (MAYBE_UNUSED const hashconfig_t *hashconfig, MAYBE_UNUSED const user_options_t *user_options, MAYBE_UNUSED const user_options_extra_t *user_options_extra)
+{
+  // this mode is so close to the 90ms edge that the autotune randomly selects a good or a bad loop count with speed loss of up to 19%.
+  // this work around helps the autotuner to find a good spot and doesn't hurt us too much since the algorithm is a little slow anyway.
+
+  const u32 kernel_loops_max = 64;
+
+  return kernel_loops_max;
+}
+
 u32 module_pw_max (MAYBE_UNUSED const hashconfig_t *hashconfig, MAYBE_UNUSED const user_options_t *user_options, MAYBE_UNUSED const user_options_extra_t *user_options_extra)
 {
   const u32 pw_max = 32;
@@ -147,7 +157,7 @@ void module_init (module_ctx_t *module_ctx)
   module_ctx->module_jit_cache_disable        = MODULE_DEFAULT;
   module_ctx->module_kernel_accel_max         = MODULE_DEFAULT;
   module_ctx->module_kernel_accel_min         = MODULE_DEFAULT;
-  module_ctx->module_kernel_loops_max         = MODULE_DEFAULT;
+  module_ctx->module_kernel_loops_max         = module_kernel_loops_max;
   module_ctx->module_kernel_loops_min         = MODULE_DEFAULT;
   module_ctx->module_kernel_threads_max       = MODULE_DEFAULT;
   module_ctx->module_kernel_threads_min       = MODULE_DEFAULT;