[LTP] [PATCH 1/2] lib: add extra calibrated runtime to slow tests

[Li Wang]

This patch inspired by Cyril's work ec14f4572d ("sched:
starvation: Autocallibrate the timeout"), introduces a CPU
calibration mechanism to enhance test runtime calculations.

The new tst_callibrate function measures CPU performance,
and in combination with tst_kconfig_debug_matches which
detects enabled debug-kernel configurations, computes an
extra_runtime adjustment.

The multiply_runtime function now incorporates this adjustment
to account for debug overhead, reducing the likelihood of
timeouts while maintaining adaptability for slower systems.

Signed-off-by: Li Wang <liwang@redhat.com>
---
 include/tst_kconfig.h | 32 ++++++++++++++++++++++++++++++++
 include/tst_timer.h   | 30 ++++++++++++++++++++++++++++++
 lib/tst_test.c        |  5 ++++-
 3 files changed, 66 insertions(+), 1 deletion(-)

diff --git a/include/tst_kconfig.h b/include/tst_kconfig.h
index 23f807409..5746925df 100644
--- a/include/tst_kconfig.h
+++ b/include/tst_kconfig.h
@@ -98,4 +98,36 @@ struct tst_kcmdline_var {
  */
 void tst_kcmdline_parse(struct tst_kcmdline_var params[], size_t params_len);
 
+/*
+ * List of debug-kernel config options that may degrade performance when enabled.
+ */
+static const char * const tst_kconf_debug_options[][2] = {
+	{"CONFIG_PROVE_LOCKING=y", NULL},
+	{"CONFIG_LOCKDEP=y", NULL},
+	{"CONFIG_DEBUG_SPINLOCK=y", NULL},
+	{"CONFIG_DEBUG_RT_MUTEXES=y", NULL},
+	{"CONFIG_DEBUG_MUTEXES=y", NULL},
+	{"CONFIG_DEBUG_PAGEALLOC=y", NULL},
+	{"CONFIG_KASAN=y", NULL},
+	{"CONFIG_SLUB_RCU_DEBUG=y", NULL},
+	{"CONFIG_TRACE_IRQFLAGS=y", NULL},
+	{"CONFIG_LATENCYTOP=y", NULL},
+	{"CONFIG_DEBUG_NET=y", NULL},
+	{"CONFIG_EXT4_DEBUG=y", NULL},
+	{"CONFIG_QUOTA_DEBUG=y", NULL},
+	{"CONFIG_FAULT_INJECTION=y", NULL},
+	{"CONFIG_DEBUG_OBJECTS=y", NULL},
+	{NULL, NULL}
+};
+
+static inline int tst_kconfig_debug_matches(void)
+{
+	int i, num = 1;
+
+	for (i = 0; tst_kconf_debug_options[i][0] != NULL; i++)
+		num += !tst_kconfig_check(tst_kconf_debug_options[i]);
+
+	return num;
+}
+
 #endif	/* TST_KCONFIG_H__ */
diff --git a/include/tst_timer.h b/include/tst_timer.h
index 6fb940020..268fc8389 100644
--- a/include/tst_timer.h
+++ b/include/tst_timer.h
@@ -17,6 +17,7 @@
 #include <mqueue.h>
 #include <time.h>
 #include "tst_test.h"
+#include "tst_clocks.h"
 #include "lapi/common_timers.h"
 #include "lapi/posix_types.h"
 #include "lapi/syscalls.h"
@@ -1074,4 +1075,33 @@ static inline long long tst_timer_elapsed_us(void)
 	return tst_timespec_to_us(tst_timer_elapsed());
 }
 
+#define CALLIBRATE_LOOPS 120000000
+
+/*
+ * Measures the time taken by the CPU to perform a specified
+ * number of empty loops for calibration.
+ */
+static inline int tst_callibrate(void)
+{
+	int i;
+	struct timespec start, stop;
+	long long diff;
+
+	for (i = 0; i < CALLIBRATE_LOOPS; i++)
+		__asm__ __volatile__ ("" : "+g" (i) : :);
+
+	tst_clock_gettime(CLOCK_MONOTONIC_RAW, &start);
+
+	for (i = 0; i < CALLIBRATE_LOOPS; i++)
+		__asm__ __volatile__ ("" : "+g" (i) : :);
+
+	tst_clock_gettime(CLOCK_MONOTONIC_RAW, &stop);
+
+	diff = tst_timespec_diff_us(stop, start);
+
+	tst_res(TINFO, "CPU did %i loops in %llius", CALLIBRATE_LOOPS, diff);
+
+	return diff;
+}
+
 #endif /* TST_TIMER */
diff --git a/lib/tst_test.c b/lib/tst_test.c
index 8db554dea..296683ffb 100644
--- a/lib/tst_test.c
+++ b/lib/tst_test.c
@@ -549,13 +549,16 @@ static void parse_mul(float *mul, const char *env_name, float min, float max)
 static int multiply_runtime(int max_runtime)
 {
 	static float runtime_mul = -1;
+	static int extra_runtime = 0;
 
 	if (max_runtime <= 0)
 		return max_runtime;
 
 	parse_mul(&runtime_mul, "LTP_RUNTIME_MUL", 0.0099, 100);
 
-	return max_runtime * runtime_mul;
+	extra_runtime = (tst_callibrate() / 1000) * tst_kconfig_debug_matches();
+
+	return (max_runtime + extra_runtime) * runtime_mul;
 }
 
 static struct option {
-- 
2.47.0