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// Copyright (c) 2010 Baidu, Inc.
//
// 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.
// Author: Ge,Jun (gejun@baidu.com)
// Date: Fri Aug 29 15:01:15 CST 2014
#include <unistd.h> // close
#include <sys/types.h> // open
#include <sys/stat.h> // ^
#include <fcntl.h> // ^
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <string.h> // memmem
#undef _GNU_SOURCE
#include "butil/time.h"
namespace butil {
int64_t monotonic_time_ns() {
// MONOTONIC_RAW is slower than MONOTONIC in linux 2.6.32, trying to
// use the RAW version does not make sense anymore.
// NOTE: Not inline to keep ABI-compatible with previous versions.
timespec now;
clock_gettime(CLOCK_MONOTONIC, &now);
return now.tv_sec * 1000000000L + now.tv_nsec;
}
namespace detail {
// read_cpu_frequency() is modified from source code of glibc.
int64_t read_cpu_frequency(bool* invariant_tsc) {
/* We read the information from the /proc filesystem. It contains at
least one line like
cpu MHz : 497.840237
or also
cpu MHz : 497.841
We search for this line and convert the number in an integer. */
const int fd = open("/proc/cpuinfo", O_RDONLY);
if (fd < 0) {
return 0;
}
int64_t result = 0;
char buf[4096]; // should be enough
const ssize_t n = read(fd, buf, sizeof(buf));
if (n > 0) {
char *mhz = static_cast<char*>(memmem(buf, n, "cpu MHz", 7));
if (mhz != NULL) {
char *endp = buf + n;
int seen_decpoint = 0;
int ndigits = 0;
/* Search for the beginning of the string. */
while (mhz < endp && (*mhz < '0' || *mhz > '9') && *mhz != '\n') {
++mhz;
}
while (mhz < endp && *mhz != '\n') {
if (*mhz >= '0' && *mhz <= '9') {
result *= 10;
result += *mhz - '0';
if (seen_decpoint)
++ndigits;
} else if (*mhz == '.') {
seen_decpoint = 1;
}
++mhz;
}
/* Compensate for missing digits at the end. */
while (ndigits++ < 6) {
result *= 10;
}
}
if (invariant_tsc) {
char* flags_pos = static_cast<char*>(memmem(buf, n, "flags", 5));
*invariant_tsc =
(flags_pos &&
memmem(flags_pos, buf + n - flags_pos, "constant_tsc", 12) &&
memmem(flags_pos, buf + n - flags_pos, "nonstop_tsc", 11));
}
}
close (fd);
return result;
}
// Return value must be >= 0
int64_t read_invariant_cpu_frequency() {
bool invariant_tsc = false;
const int64_t freq = read_cpu_frequency(&invariant_tsc);
if (!invariant_tsc || freq < 0) {
return 0;
}
return freq;
}
int64_t invariant_cpu_freq = -1;
} // namespace detail
} // namespace butil