From 53e927c20245300607cb5c87ef273d77989eb13e Mon Sep 17 00:00:00 2001
From: Laurent MAZET <laurent.mazet@thalesgroup.com>
Date: Thu, 16 Oct 2025 16:34:45 +0200
Subject: [PATCH] estimate sched clock

---
 load.c  | 52 ++++++++++++++++++++++++++++++++++---
 rdtsc.h | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 127 insertions(+), 4 deletions(-)
 create mode 100644 rdtsc.h

diff --git a/load.c b/load.c
index e5f6c72..ff39552 100644
--- a/load.c
+++ b/load.c
@@ -1,6 +1,6 @@
 /* depend: */
 /* cflags: */
-/* linker: -lpthread */
+/* linker: mtime.o -lpthread */
 
 #include <assert.h>
 //#include <math.h>
@@ -8,8 +8,11 @@
 #include <sched.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <sys/time.h>
 #include <unistd.h>
 
+#include "rdtsc.h"
+
 /* constants */
 
 //#define N 32
@@ -23,6 +26,7 @@ char *version = "0.1";
 
 int nb_threads = 1;
 int sched_rt_prio = 50;
+int mode = 0;
 
 /* types */
 
@@ -36,11 +40,12 @@ typedef struct {
 int usage (int ret)
 {
     FILE *fd = ret ? stderr : stdout;
-    fprintf (fd, "usage: %s [-h] [-n int] [-v]\n", progname);
+    fprintf (fd, "usage: %s [-c] [-h] [-n int] [-r int] [-v]\n", progname);
+    fprintf (fd, " -c: estimate clock\n");
     fprintf (fd, " -h: help message\n");
     fprintf (fd, " -n: number of thread (%d)\n", nb_threads);
-    fprintf (fd, " -n: print version\n");
     fprintf (fd, " -r: real-time priority, -1 to desactivate (%d)\n", sched_rt_prio);
+    fprintf (fd, " -v: print version\n");
     fprintf (fd, "%s version %s\n", progname, version);
 
     return ret;
@@ -141,10 +146,41 @@ void *work (__attribute__((unused)) void *arg)
         generate_matrix (matrix);
         double det = determinant (matrix);
         printf ("det: %g\n", det);
+        free_matrix (matrix);
     }
     pthread_exit (NULL);
 }
 
+double estimate_clock (void)
+{
+    int n = 4;
+    int64_t diff_nc = 0;
+    double clock = 0;
+    while ((diff_nc < 1000) && (n < 13)) {
+
+        struct timeval tv1;
+        gettimeofday (&tv1, NULL);
+        //sys_timestamp (&ts1);
+        int64_t nc1 = rdtsc ();
+
+        matrix_t *matrix = alloc_matrix (n++);
+        generate_matrix (matrix);
+        determinant (matrix);
+        free_matrix (matrix);
+
+        struct timeval tv2;
+        gettimeofday (&tv2, NULL);
+        int64_t nc2 = rdtsc ();
+
+        diff_nc = nc2 - nc1;
+        double delta = ((double)tv2.tv_sec + tv2.tv_usec * 1e-6) -
+            ((double)tv1.tv_sec + tv1.tv_usec * 1e-6);
+        clock = diff_nc / delta;
+    }
+
+    return clock;
+}
+
 /* main function */
 
 int main (int argc, char *argv[])
@@ -170,6 +206,10 @@ int main (int argc, char *argv[])
         }
         char c = arg[1];
         switch (c) {
+        case 'c':
+            arg = (arg[2]) ? arg + 2 : (--argc > 0) ? *(++argv) : NULL;
+            mode = (arg == NULL) ? 1 : atoi (arg);
+            break;
         case 'n':
             arg = (arg[2]) ? arg + 2 : (--argc > 0) ? *(++argv) : NULL;
             if (arg == NULL) {
@@ -216,7 +256,11 @@ int main (int argc, char *argv[])
 
     /* main process */
 
-    if (nb_threads == 0) {
+    if (mode)  {
+        while (mode--) {
+            printf ("Clock: %.0fMHz\n", estimate_clock () / 1e6);
+        }
+    } else if (nb_threads == 0) {
         while (1) {
             sleep (60);
         }
diff --git a/rdtsc.h b/rdtsc.h
new file mode 100644
index 0000000..35165aa
--- /dev/null
+++ b/rdtsc.h
@@ -0,0 +1,79 @@
+/*
+  File name        : rdtsc.h
+  Date of creation : 26/1/2012
+  Version          : 1.0
+  Copyright        : Soft'n'design
+  Author           : Laurent Mazet <mazet@softndesign.org>
+
+  Description      : This file contains rdtsc inline function
+
+  History          :
+  - initial version
+*/
+
+#ifndef __RDTSC_H__
+#define __RDTSC_H__
+
+#include <stdint.h>
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+/**
+    Get RDTSC counter
+
+    @return counter
+*/
+#if defined(__i386__)
+static __inline__ int64_t rdtsc (void) {
+     int64_t x;
+     __asm__ volatile ("rdtsc" : "=A" (x));
+     return x;
+}
+#elif defined(__amd64__)
+static __inline__ int64_t rdtsc (void) {
+     int64_t a, d;
+     __asm__ volatile ("rdtsc" : "=a" (a), "=d" (d));
+     return (d << 32) | a;
+}
+#elif defined(__PPC64__)
+static __inline__ int64_t rdtsc (void) {
+     int64_t x;
+     __asm__ volatile ("mfspr %0, 268\n" : "=r" (x));
+     return x;
+}
+#elif defined(__x86_64__)
+static __inline__ int64_t rdtsc (void) {
+     int64_t a, d;
+     __asm__ volatile ("lfence");
+     __asm__ volatile ("rdtsc" : "=a" (a), "=d" (d));
+     return (d << 32) | a;
+}
+#elif defined(__aarch64__)
+static __inline__ int64_t rdtsc (void) {
+     int64_t x;
+     //__asm__ volatile ("isb" : : : "memory");
+     //__asm__ volatile ("mrs %0, cntvct_el0" : "=r" (x) :: "memory");
+     //__asm__ volatile ("isb" : : : "memory");
+     __asm__ volatile ("mrs %0, cntvct_el0" : "=r" (x));
+     return x;
+}
+#elif defined(__arm__)
+static __inline__ int64_t rdtsc (void) {
+     int32_t a, d = 0;
+     __asm__ volatile ("mrrc p15, 1, %0, %1, c14" : "=r"(a), "=r"(d));
+     //__asm__ volatile ("mrc p15, 0, %0, c9, c13, 0" : "=r"(a));
+     return ((int64_t)d << 32) | (int64_t)a;
+}
+#else
+static __inline__ int64_t rdtsc (void) {
+     static int64_t a = 0;
+     return a++;
+}
+#endif
+
+__END_DECLS
+
+#endif /* __RDTSC_H__ */
+
+/* vi:set tabstop=4 expandtab shiftwidth=4: this line set vi mode */
-- 
2.30.2