lib: multiply the max_runtime if detect slow kconfigs

The method adjusts the max_runtime for test cases by multiplying
it by a factor (4x) if any slower kernel options are detected.
Debug kernel configurations (such as CONFIG_KASAN, CONFIG_PROVE_LOCKING, etc.)
are known to degrade performance, and this adjustment ensures
that tests do not fail prematurely due to timeouts.

As Cyril pointed out that a debug kernel will typically run
slower by a factor of N, and while determining the exact value
of N is challenging, so a reasonable upper bound is sufficient
for practical purposes.

Signed-off-by: Li Wang <[email protected]>
Reviewed-by: Petr Vorel <[email protected]>
Reviewed-by: Cyril Hrubis <[email protected]>

include/tst_kconfig.h

@@ -98,4 +98,16 @@ struct tst_kcmdline_var {
  */
 void tst_kcmdline_parse(struct tst_kcmdline_var params[], size_t params_len);
 
+/*
+ * tst_has_slow_kconfig() - Check if any performance-degrading kernel configs are enabled.
+ *
+ * This function iterates over the list of slow kernel configuration options
+ * (`tst_slow_kconfigs`) and checks if any of them are enabled in the running kernel.
+ *
+ * Return:
+ * - 1 if at least one slow kernel config is enabled.
+ * - 0 if none of the slow kernel configs are enabled.
+ */
+int tst_has_slow_kconfig(void);
+
 #endif	/* TST_KCONFIG_H__ */

lib/tst_kconfig.c

@@ -631,3 +631,41 @@ void tst_kcmdline_parse(struct tst_kcmdline_var params[], size_t params_len)
 
 	SAFE_FCLOSE(f);
 }
+
+/*
+ * List of kernel config options that may degrade performance when enabled.
+ */
+static struct tst_kconfig_var slow_kconfigs[] = {
+	TST_KCONFIG_INIT("CONFIG_PROVE_LOCKING"),
+	TST_KCONFIG_INIT("CONFIG_LOCKDEP"),
+	TST_KCONFIG_INIT("CONFIG_DEBUG_SPINLOCK"),
+	TST_KCONFIG_INIT("CONFIG_DEBUG_RT_MUTEXES"),
+	TST_KCONFIG_INIT("CONFIG_DEBUG_MUTEXES"),
+	TST_KCONFIG_INIT("CONFIG_KASAN"),
+	TST_KCONFIG_INIT("CONFIG_SLUB_RCU_DEBUG"),
+	TST_KCONFIG_INIT("CONFIG_TRACE_IRQFLAGS"),
+	TST_KCONFIG_INIT("CONFIG_LATENCYTOP"),
+	TST_KCONFIG_INIT("CONFIG_DEBUG_NET"),
+	TST_KCONFIG_INIT("CONFIG_EXT4_DEBUG"),
+	TST_KCONFIG_INIT("CONFIG_QUOTA_DEBUG"),
+	TST_KCONFIG_INIT("CONFIG_FAULT_INJECTION"),
+	TST_KCONFIG_INIT("CONFIG_DEBUG_OBJECTS")
+};
+
+int tst_has_slow_kconfig(void)
+{
+	unsigned int i;
+
+	tst_kconfig_read(slow_kconfigs, ARRAY_SIZE(slow_kconfigs));
+
+	for (i = 0; i < ARRAY_SIZE(slow_kconfigs); i++) {
+		if (slow_kconfigs[i].choice == 'y') {
+			tst_res(TINFO,
+				"%s kernel option detected which might slow the execution",
+				slow_kconfigs[i].id);
+			return 1;
+		}
+	}
+
+	return 0;
+}

lib/tst_test.c

@@ -555,6 +555,9 @@ static int multiply_runtime(int max_runtime)
 
 	parse_mul(&runtime_mul, "LTP_RUNTIME_MUL", 0.0099, 100);
 
+	if (tst_has_slow_kconfig())
+		max_runtime *= 4;
+
 	return max_runtime * runtime_mul;
 }