X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;f=src%2Fvppinfra%2Ftime.c;h=35852a61cdfe07b2e8d6d55fe18b1951b45f08ee;hb=12e3e312b1c9ea83342a504786e0eb36ede2d9d5;hp=dee5002497537b00ccc46b5954c33a01edbb1564;hpb=96e2d4407b1538d8df4e277ba33b85876589e198;p=vpp.git

diff --git a/src/vppinfra/time.c b/src/vppinfra/time.c
index dee50024975..35852a61cdf 100644
--- a/src/vppinfra/time.c
+++ b/src/vppinfra/time.c
@@ -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);
 
@@ -198,6 +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 save_total_cpu_time_in_seconds;
 
   c->last_verify_cpu_time = c->last_cpu_time;
   c->last_verify_reference_time = now_reference;
@@ -239,10 +272,12 @@ clib_time_verify_frequency (clib_time_t * c)
     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%%",
@@ -251,11 +286,19 @@ clib_time_verify_frequency (clib_time_t * c)
       return;
     }
 
-  c->clocks_per_second =
-    flt_round_nearest ((f64) dtc / (dtr * c->round_to_units))
-    * c->round_to_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;