X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;f=src%2Fvppinfra%2Ftime.c;h=35852a61cdfe07b2e8d6d55fe18b1951b45f08ee;hb=12e3e312b1c9ea83342a504786e0eb36ede2d9d5;hp=afb1a867ec77ebb481b7a992b9fb1d8793cc94e5;hpb=b7b929931a07fbb27b43d5cd105f366c3e29807e;p=vpp.git

diff --git a/src/vppinfra/time.c b/src/vppinfra/time.c
index afb1a867ec7..35852a61cdf 100644
--- a/src/vppinfra/time.c
+++ b/src/vppinfra/time.c
@@ -120,7 +120,7 @@ clock_frequency_from_proc_filesystem (void)
 static f64
 clock_frequency_from_sys_filesystem (void)
 {
-  f64 cpu_freq;
+  f64 cpu_freq = 0.0;
   int fd;
   unformat_input_t input;
 
@@ -131,7 +131,7 @@ clock_frequency_from_sys_filesystem (void)
     goto done;
 
   unformat_init_clib_file (&input, fd);
-  unformat (&input, "%f", &cpu_freq);
+  (void) unformat (&input, "%f", &cpu_freq);
   cpu_freq *= 1e3;		/* measured in kHz */
   unformat_free (&input);
   close (fd);
@@ -153,6 +153,38 @@ os_cpu_clock_frequency (void)
 #endif
   f64 cpu_freq;
 
+#ifdef __x86_64__
+  u32 __clib_unused eax = 0, ebx = 0, ecx = 0, edx = 0;
+  clib_get_cpuid (0x00, &eax, &ebx, &ecx, &edx);
+  if (eax >= 0x15)
+    {
+      u32 max_leaf = eax;
+      /*
+         CPUID Leaf 0x15 - Time Stamp Counter and Nominal Core Crystal Clock Info
+         eax - denominator of the TSC/”core crystal clock” ratio
+         ebx - numerator of the TSC/”core crystal clock” ratio
+         ecx - nominal frequency of the core crystal clock in Hz
+         edx - reseved
+       */
+
+      clib_get_cpuid (0x15, &eax, &ebx, &ecx, &edx);
+      if (ebx && ecx)
+	return ecx * ebx / eax;
+
+      if (max_leaf >= 0x16)
+	{
+	  /*
+	     CPUID Leaf 0x16 - Processor Frequency Information Leaf
+	     eax - Bits 15 - 00: Processor Base Frequency (in MHz).
+	   */
+
+	  clib_get_cpuid (0x16, &eax, &ebx, &ecx, &edx);
+	  if (eax)
+	    return 1e6 * (eax & 0xffff);
+	}
+    }
+#endif
+
   if (clib_cpu_supports_invariant_tsc ())
     return estimate_clock_frequency (1e-3);
 
@@ -198,7 +230,7 @@ clib_time_verify_frequency (clib_time_t * c)
   f64 dtr_max;
   u64 dtc = c->last_cpu_time - c->last_verify_cpu_time;
   f64 new_clocks_per_second, delta;
-  f64 round_units = 100e5;
+  f64 save_total_cpu_time_in_seconds;
 
   c->last_verify_cpu_time = c->last_cpu_time;
   c->last_verify_reference_time = now_reference;
@@ -218,17 +250,34 @@ clib_time_verify_frequency (clib_time_t * c)
       return;
     }
 
+  if (PREDICT_FALSE (c->round_to_units == 0.0))
+    {
+      f64 next_pow10, est_round_to_units;
+      /*
+       * Compute the first power of ten which is greater than
+       * 0.1% of the new clock rate. Save the result, and use it
+       * to round future results, so we don't end up calculating
+       * silly-looking clock rates.
+       */
+      est_round_to_units = ((f64) dtc / dtr) * 0.001;
+      next_pow10 = ceil (log10 (est_round_to_units));
+      c->round_to_units = pow (10.0, next_pow10);
+    }
+
   /*
    * Reject large frequency changes, another consequence of
    * system clock changes particularly with old kernels.
    */
   new_clocks_per_second =
-    flt_round_nearest ((f64) dtc / (dtr * round_units)) * round_units;
+    flt_round_nearest ((f64) dtc / (dtr * c->round_to_units))
+    * c->round_to_units;
 
+  /* Compute abs(rate change) */
   delta = new_clocks_per_second - c->clocks_per_second;
   if (delta < 0.0)
     delta = -delta;
 
+  /* If rate change > 1%, reject it and try again */
   if (PREDICT_FALSE ((delta / c->clocks_per_second) > .01))
     {
       clib_warning ("Rejecting large frequency change of %.2f%%",
@@ -237,10 +286,19 @@ clib_time_verify_frequency (clib_time_t * c)
       return;
     }
 
-  c->clocks_per_second =
-    flt_round_nearest ((f64) dtc / (dtr * round_units)) * round_units;
+  /* Save total cpu time in seconds */
+  save_total_cpu_time_in_seconds = c->total_cpu_time * c->seconds_per_clock;
+
+  /* Recalculate clock rate */
+  c->clocks_per_second = new_clocks_per_second;
   c->seconds_per_clock = 1 / c->clocks_per_second;
 
+  /*
+   * Restore total cpu time in seconds. Otherwise, if c->clocks_per_second
+   * has decreased, time may appear to flow backwards.
+   */
+  c->total_cpu_time = save_total_cpu_time_in_seconds * c->clocks_per_second;
+
   /* Double time between verifies; max at 64 secs ~ 1 minute. */
   if (c->log2_clocks_per_frequency_verify < c->log2_clocks_per_second + 6)
     c->log2_clocks_per_frequency_verify += 1;