1 files changed, 226 insertions, 0 deletions
diff --git a/src/vppinfra/time.c b/src/vppinfra/time.c
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+/*
+ * Copyright (c) 2015 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+/*
+  Copyright (c) 2005 Eliot Dresselhaus
+
+  Permission is hereby granted, free of charge, to any person obtaining
+  a copy of this software and associated documentation files (the
+  "Software"), to deal in the Software without restriction, including
+  without limitation the rights to use, copy, modify, merge, publish,
+  distribute, sublicense, and/or sell copies of the Software, and to
+  permit persons to whom the Software is furnished to do so, subject to
+  the following conditions:
+
+  The above copyright notice and this permission notice shall be
+  included in all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+#include <vppinfra/os.h>
+#include <vppinfra/time.h>
+#include <vppinfra/format.h>
+#include <vppinfra/cpu.h>
+
+#ifdef CLIB_UNIX
+
+#include <math.h>
+#include <sys/time.h>
+#include <fcntl.h>
+
+/* Not very accurate way of determining cpu clock frequency
+   for unix.  Better to use /proc/cpuinfo on linux. */
+static f64
+estimate_clock_frequency (f64 sample_time)
+{
+  /* Round to nearest 100KHz. */
+  const f64 round_to_units = 100e5;
+
+  f64 time_now, time_start, time_limit, freq;
+  u64 ifreq, t[2];
+
+  time_start = time_now = unix_time_now ();
+  time_limit = time_now + sample_time;
+  t[0] = clib_cpu_time_now ();
+  while (time_now < time_limit)
+    time_now = unix_time_now ();
+  t[1] = clib_cpu_time_now ();
+
+  freq = (t[1] - t[0]) / (time_now - time_start);
+  ifreq = flt_round_nearest (freq / round_to_units);
+  freq = ifreq * round_to_units;
+
+  return freq;
+}
+
+/* Fetch cpu frequency via parseing /proc/cpuinfo.
+   Only works for Linux. */
+static f64
+clock_frequency_from_proc_filesystem (void)
+{
+  f64 cpu_freq = 1e9;		/* better than 40... */
+  f64 ppc_timebase = 0;		/* warnings be gone */
+  int fd;
+  unformat_input_t input;
+
+/* $$$$ aarch64 kernel doesn't report "cpu MHz" */
+#if defined(__aarch64__)
+  return 0.0;
+#endif
+
+  cpu_freq = 0;
+  fd = open ("/proc/cpuinfo", 0);
+  if (fd < 0)
+    return cpu_freq;
+
+  unformat_init_unix_file (&input, fd);
+
+  ppc_timebase = 0;
+  while (unformat_check_input (&input) != UNFORMAT_END_OF_INPUT)
+    {
+      if (unformat (&input, "cpu MHz : %f", &cpu_freq))
+	cpu_freq *= 1e6;
+      else if (unformat (&input, "timebase : %f", &ppc_timebase))
+	;
+      else
+	unformat_skip_line (&input);
+    }
+
+  unformat_free (&input);
+
+  close (fd);
+
+  /* Override CPU frequency with time base for PPC. */
+  if (ppc_timebase != 0)
+    cpu_freq = ppc_timebase;
+
+  return cpu_freq;
+}
+
+/* Fetch cpu frequency via reading /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq
+   Only works for Linux. */
+static f64
+clock_frequency_from_sys_filesystem (void)
+{
+  f64 cpu_freq;
+  int fd;
+  unformat_input_t input;
+
+  /* Time stamp always runs at max frequency. */
+  cpu_freq = 0;
+  fd = open ("/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq", 0);
+  if (fd < 0)
+    goto done;
+
+  unformat_init_unix_file (&input, fd);
+  unformat (&input, "%f", &cpu_freq);
+  cpu_freq *= 1e3;		/* measured in kHz */
+  unformat_free (&input);
+  close (fd);
+done:
+  return cpu_freq;
+}
+
+f64
+os_cpu_clock_frequency (void)
+{
+  f64 cpu_freq;
+
+  if (clib_cpu_supports_invariant_tsc ())
+    return estimate_clock_frequency (1e-3);
+
+  /* First try /sys version. */
+  cpu_freq = clock_frequency_from_sys_filesystem ();
+  if (cpu_freq != 0)
+    return cpu_freq;
+
+  /* Next try /proc version. */
+  cpu_freq = clock_frequency_from_proc_filesystem ();
+  if (cpu_freq != 0)
+    return cpu_freq;
+
+  /* If /proc/cpuinfo fails (e.g. not running on Linux) fall back to
+     gettimeofday based estimated clock frequency. */
+  return estimate_clock_frequency (1e-3);
+}
+
+#endif /* CLIB_UNIX */
+
+/* Initialize time. */
+void
+clib_time_init (clib_time_t * c)
+{
+  memset (c, 0, sizeof (c[0]));
+  c->clocks_per_second = os_cpu_clock_frequency ();
+  c->seconds_per_clock = 1 / c->clocks_per_second;
+  c->log2_clocks_per_second = min_log2_u64 ((u64) c->clocks_per_second);
+
+  /* Initially verify frequency every sec */
+  c->log2_clocks_per_frequency_verify = c->log2_clocks_per_second;
+
+  c->last_verify_reference_time = unix_time_now ();
+  c->last_cpu_time = clib_cpu_time_now ();
+  c->init_cpu_time = c->last_verify_cpu_time = c->last_cpu_time;
+}
+
+void
+clib_time_verify_frequency (clib_time_t * c)
+{
+  f64 now_reference = unix_time_now ();
+  f64 dtr = now_reference - c->last_verify_reference_time;
+  f64 dtr_max;
+  u64 dtc = c->last_cpu_time - c->last_verify_cpu_time;
+  f64 round_units = 100e5;
+
+  c->last_verify_cpu_time = c->last_cpu_time;
+  c->last_verify_reference_time = now_reference;
+
+  /*
+   * Is the reported reference interval non-positive,
+   * or off by a factor of two - or 8 seconds - whichever is larger?
+   * Someone reset the clock behind our back.
+   */
+  dtr_max = (f64) (2ULL << c->log2_clocks_per_frequency_verify) /
+    (f64) (1ULL << c->log2_clocks_per_second);
+  dtr_max = dtr_max > 8.0 ? dtr_max : 8.0;
+
+  if (dtr <= 0.0 || dtr > dtr_max)
+    {
+      c->log2_clocks_per_frequency_verify = c->log2_clocks_per_second;
+      return;
+    }
+
+  c->clocks_per_second =
+    flt_round_nearest ((f64) dtc / (dtr * round_units)) * round_units;
+  c->seconds_per_clock = 1 / 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;
+}
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */