[LTP] [PATCH V3] lib: multiply the max_runtime if detect slow kconfigs

[Li Wang]

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 <liwang@redhat.com>
---
 include/tst_kconfig.h | 13 +++++++++++++
 lib/tst_kconfig.c     | 39 +++++++++++++++++++++++++++++++++++++++
 lib/tst_test.c        |  3 +++
 3 files changed, 55 insertions(+)

diff --git a/include/tst_kconfig.h b/include/tst_kconfig.h
index 23f807409..291c34b11 100644
--- a/include/tst_kconfig.h
+++ b/include/tst_kconfig.h
@@ -98,4 +98,17 @@ struct tst_kcmdline_var {
  */
 void tst_kcmdline_parse(struct tst_kcmdline_var params[], size_t params_len);
 
+/*
+ * 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.
+ * These options are known to degrade system performance when enabled.
+ *
+ * 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__ */
diff --git a/lib/tst_kconfig.c b/lib/tst_kconfig.c
index 6d6b1da18..92c27cb35 100644
--- a/lib/tst_kconfig.c
+++ b/lib/tst_kconfig.c
@@ -631,3 +631,42 @@ 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_DEBUG_PAGEALLOC"),
+	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",
+				slow_kconfigs[i].id);
+			return 1;
+		}
+	}
+
+	return 0;
+}
diff --git a/lib/tst_test.c b/lib/tst_test.c
index 8db554dea..f4e667240 100644
--- a/lib/tst_test.c
+++ b/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;
 }
 
-- 
2.47.0