FD.io VPP  v20.01-48-g3e0dafb74
Vector Packet Processing
time.c
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1 /*
2  * Copyright (c) 2015 Cisco and/or its affiliates.
3  * Licensed under the Apache License, Version 2.0 (the "License");
4  * you may not use this file except in compliance with the License.
5  * You may obtain a copy of the License at:
6  *
7  * http://www.apache.org/licenses/LICENSE-2.0
8  *
9  * Unless required by applicable law or agreed to in writing, software
10  * distributed under the License is distributed on an "AS IS" BASIS,
11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12  * See the License for the specific language governing permissions and
13  * limitations under the License.
14  */
15 /*
16  Copyright (c) 2005 Eliot Dresselhaus
17 
18  Permission is hereby granted, free of charge, to any person obtaining
19  a copy of this software and associated documentation files (the
20  "Software"), to deal in the Software without restriction, including
21  without limitation the rights to use, copy, modify, merge, publish,
22  distribute, sublicense, and/or sell copies of the Software, and to
23  permit persons to whom the Software is furnished to do so, subject to
24  the following conditions:
25 
26  The above copyright notice and this permission notice shall be
27  included in all copies or substantial portions of the Software.
28 
29  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
30  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
31  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
32  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
33  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
34  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
35  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
36 */
37 
38 #include <vppinfra/os.h>
39 #include <vppinfra/time.h>
40 #include <vppinfra/format.h>
41 #include <vppinfra/cpu.h>
42 
43 #ifdef CLIB_UNIX
44 
45 #include <math.h>
46 #include <sys/time.h>
47 #include <fcntl.h>
48 
49 /* Not very accurate way of determining cpu clock frequency
50  for unix. Better to use /proc/cpuinfo on linux. */
51 static f64
53 {
54  /* Round to nearest 100KHz. */
55  const f64 round_to_units = 100e5;
56 
57  f64 time_now, time_start, time_limit, freq;
58  u64 ifreq, t[2];
59 
60  time_start = time_now = unix_time_now ();
61  time_limit = time_now + sample_time;
62  t[0] = clib_cpu_time_now ();
63  while (time_now < time_limit)
64  time_now = unix_time_now ();
65  t[1] = clib_cpu_time_now ();
66 
67  freq = (t[1] - t[0]) / (time_now - time_start);
68  ifreq = flt_round_nearest (freq / round_to_units);
69  freq = ifreq * round_to_units;
70 
71  return freq;
72 }
73 
74 /* Fetch cpu frequency via parseing /proc/cpuinfo.
75  Only works for Linux. */
76 static f64
78 {
79  f64 cpu_freq = 1e9; /* better than 40... */
80  f64 ppc_timebase = 0; /* warnings be gone */
81  int fd;
82  unformat_input_t input;
83 
84 /* $$$$ aarch64 kernel doesn't report "cpu MHz" */
85 #if defined(__aarch64__)
86  return 0.0;
87 #endif
88 
89  cpu_freq = 0;
90  fd = open ("/proc/cpuinfo", 0);
91  if (fd < 0)
92  return cpu_freq;
93 
94  unformat_init_clib_file (&input, fd);
95 
96  ppc_timebase = 0;
98  {
99  if (unformat (&input, "cpu MHz : %f", &cpu_freq))
100  cpu_freq *= 1e6;
101  else if (unformat (&input, "timebase : %f", &ppc_timebase))
102  ;
103  else
104  unformat_skip_line (&input);
105  }
106 
107  unformat_free (&input);
108 
109  close (fd);
110 
111  /* Override CPU frequency with time base for PPC. */
112  if (ppc_timebase != 0)
113  cpu_freq = ppc_timebase;
114 
115  return cpu_freq;
116 }
117 
118 /* Fetch cpu frequency via reading /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq
119  Only works for Linux. */
120 static f64
122 {
123  f64 cpu_freq = 0.0;
124  int fd;
125  unformat_input_t input;
126 
127  /* Time stamp always runs at max frequency. */
128  cpu_freq = 0;
129  fd = open ("/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq", 0);
130  if (fd < 0)
131  goto done;
132 
133  unformat_init_clib_file (&input, fd);
134  (void) unformat (&input, "%f", &cpu_freq);
135  cpu_freq *= 1e3; /* measured in kHz */
136  unformat_free (&input);
137  close (fd);
138 done:
139  return cpu_freq;
140 }
141 
142 f64
144 {
145 #if defined (__aarch64__)
146  /* The system counter increments at a fixed frequency. It is distributed
147  * to each core which has registers for reading the current counter value
148  * as well as the clock frequency. The system counter is not clocked at
149  * the same frequency as the core. */
150  u64 hz;
151  asm volatile ("mrs %0, cntfrq_el0":"=r" (hz));
152  return (f64) hz;
153 #endif
154  f64 cpu_freq;
155 
156  if (clib_cpu_supports_invariant_tsc ())
157  return estimate_clock_frequency (1e-3);
158 
159  /* First try /sys version. */
161  if (cpu_freq != 0)
162  return cpu_freq;
163 
164  /* Next try /proc version. */
166  if (cpu_freq != 0)
167  return cpu_freq;
168 
169  /* If /proc/cpuinfo fails (e.g. not running on Linux) fall back to
170  gettimeofday based estimated clock frequency. */
171  return estimate_clock_frequency (1e-3);
172 }
173 
174 #endif /* CLIB_UNIX */
175 
176 /* Initialize time. */
177 void
179 {
180  clib_memset (c, 0, sizeof (c[0]));
184 
185  /* Initially verify frequency every sec */
187 
191 }
192 
193 void
195 {
196  f64 now_reference = unix_time_now ();
197  f64 dtr = now_reference - c->last_verify_reference_time;
198  f64 dtr_max;
199  u64 dtc = c->last_cpu_time - c->last_verify_cpu_time;
200  f64 new_clocks_per_second, delta;
201  f64 save_total_cpu_time_in_seconds;
202 
204  c->last_verify_reference_time = now_reference;
205 
206  /*
207  * Is the reported reference interval non-positive,
208  * or off by a factor of two - or 8 seconds - whichever is larger?
209  * Someone reset the clock behind our back.
210  */
211  dtr_max = (f64) (2ULL << c->log2_clocks_per_frequency_verify) /
212  (f64) (1ULL << c->log2_clocks_per_second);
213  dtr_max = dtr_max > 8.0 ? dtr_max : 8.0;
214 
215  if (dtr <= 0.0 || dtr > dtr_max)
216  {
218  return;
219  }
220 
221  if (PREDICT_FALSE (c->round_to_units == 0.0))
222  {
223  f64 next_pow10, est_round_to_units;
224  /*
225  * Compute the first power of ten which is greater than
226  * 0.1% of the new clock rate. Save the result, and use it
227  * to round future results, so we don't end up calculating
228  * silly-looking clock rates.
229  */
230  est_round_to_units = ((f64) dtc / dtr) * 0.001;
231  next_pow10 = ceil (log10 (est_round_to_units));
232  c->round_to_units = pow (10.0, next_pow10);
233  }
234 
235  /*
236  * Reject large frequency changes, another consequence of
237  * system clock changes particularly with old kernels.
238  */
239  new_clocks_per_second =
240  flt_round_nearest ((f64) dtc / (dtr * c->round_to_units))
241  * c->round_to_units;
242 
243  /* Compute abs(rate change) */
244  delta = new_clocks_per_second - c->clocks_per_second;
245  if (delta < 0.0)
246  delta = -delta;
247 
248  /* If rate change > 1%, reject it and try again */
249  if (PREDICT_FALSE ((delta / c->clocks_per_second) > .01))
250  {
251  clib_warning ("Rejecting large frequency change of %.2f%%",
252  (delta / c->clocks_per_second) * 100.0);
254  return;
255  }
256 
257  /* Save total cpu time in seconds */
258  save_total_cpu_time_in_seconds = c->total_cpu_time * c->seconds_per_clock;
259 
260  /* Recalculate clock rate */
261  c->clocks_per_second = new_clocks_per_second;
263 
264  /*
265  * Restore total cpu time in seconds. Otherwise, if c->clocks_per_second
266  * has decreased, time may appear to flow backwards.
267  */
268  c->total_cpu_time = save_total_cpu_time_in_seconds * c->clocks_per_second;
269 
270  /* Double time between verifies; max at 64 secs ~ 1 minute. */
273 }
274 
275 /*
276  * fd.io coding-style-patch-verification: ON
277  *
278  * Local Variables:
279  * eval: (c-set-style "gnu")
280  * End:
281  */
unsigned long u64
Definition: types.h:89
clib_memset(h->entries, 0, sizeof(h->entries[0]) *entries)
f64 clocks_per_second
Definition: time.h:53
static u64 clib_cpu_time_now(void)
Definition: time.h:75
u32 log2_clocks_per_second
Definition: time.h:69
void unformat_init_clib_file(unformat_input_t *input, int file_descriptor)
Definition: unformat.c:1064
u64 last_verify_cpu_time
Definition: time.h:64
double f64
Definition: types.h:142
static void unformat_skip_line(unformat_input_t *i)
Definition: format.h:222
static f64 unix_time_now(void)
Definition: time.h:249
static u64 min_log2_u64(u64 x)
Definition: clib.h:200
u32 log2_clocks_per_frequency_verify
Definition: time.h:69
struct _unformat_input_t unformat_input_t
#define PREDICT_FALSE(x)
Definition: clib.h:111
f64 seconds_per_clock
Definition: time.h:57
void clib_time_init(clib_time_t *c)
Definition: time.c:178
u64 total_cpu_time
Definition: time.h:47
void clib_time_verify_frequency(clib_time_t *c)
Definition: time.c:194
#define UNFORMAT_END_OF_INPUT
Definition: format.h:145
svmdb_client_t * c
#define clib_warning(format, args...)
Definition: error.h:59
static f64 clock_frequency_from_sys_filesystem(void)
Definition: time.c:121
u64 last_cpu_time
Definition: time.h:50
f64 os_cpu_clock_frequency(void)
Definition: time.c:143
static f64 clock_frequency_from_proc_filesystem(void)
Definition: time.c:77
f64 last_verify_reference_time
Definition: time.h:67
static word flt_round_nearest(f64 x)
Definition: clib.h:277
static f64 estimate_clock_frequency(f64 sample_time)
Definition: time.c:52
static void unformat_free(unformat_input_t *i)
Definition: format.h:163
u64 init_cpu_time
Definition: time.h:62
f64 round_to_units
Definition: time.h:59
uword unformat(unformat_input_t *i, const char *fmt,...)
Definition: unformat.c:978
static uword unformat_check_input(unformat_input_t *i)
Definition: format.h:171