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//
//
// Copyright 2015 gRPC authors.
//
// 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.
//
//
#include <grpc/support/port_platform.h>
#if GPR_LINUX
#include <fcntl.h>
#include <unistd.h>
#endif
#include <algorithm>
#include <grpc/support/log.h>
#include <grpc/support/time.h>
#include "src/core/lib/gpr/time_precise.h"
#include "src/core/lib/gprpp/crash.h"
#ifndef GPR_CYCLE_COUNTER_CUSTOM
#if GPR_CYCLE_COUNTER_RDTSC_32 || GPR_CYCLE_COUNTER_RDTSC_64
#if GPR_LINUX
static bool read_freq_from_kernel(double* freq) {
// Google production kernel export the frequency for us in kHz.
int fd = open("/sys/devices/system/cpu/cpu0/tsc_freq_khz", O_RDONLY);
if (fd == -1) {
return false;
}
char line[1024] = {};
char* err;
bool ret = false;
int len = read(fd, line, sizeof(line) - 1);
if (len > 0) {
const long val = strtol(line, &err, 10);
if (line[0] != '\0' && (*err == '\n' || *err == '\0')) {
*freq = val * 1e3; // Value is kHz.
ret = true;
}
}
close(fd);
return ret;
}
#endif // GPR_LINUX
static double cycles_per_second = 0;
static gpr_cycle_counter start_cycle;
static bool is_fake_clock() {
gpr_timespec start = gpr_now(GPR_CLOCK_MONOTONIC);
int64_t sum = 0;
for (int i = 0; i < 8; ++i) {
gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC);
gpr_timespec delta = gpr_time_sub(now, start);
sum += delta.tv_sec * GPR_NS_PER_SEC + delta.tv_nsec;
}
// If the clock doesn't move even a nano after 8 tries, it's a fake one.
return sum == 0;
}
void gpr_precise_clock_init(void) {
gpr_log(GPR_DEBUG, "Calibrating timers");
#if GPR_LINUX
if (read_freq_from_kernel(&cycles_per_second)) {
start_cycle = gpr_get_cycle_counter();
return;
}
#endif // GPR_LINUX
if (is_fake_clock()) {
cycles_per_second = 1;
start_cycle = 0;
return;
}
// Start from a loop of 1ms, and gradually increase the loop duration
// until we either converge or we have passed 255ms (1ms+2ms+...+128ms).
int64_t measurement_ns = GPR_NS_PER_MS;
double last_freq = -1;
bool converged = false;
for (int i = 0; i < 8 && !converged; ++i, measurement_ns *= 2) {
start_cycle = gpr_get_cycle_counter();
int64_t loop_ns;
gpr_timespec start = gpr_now(GPR_CLOCK_MONOTONIC);
do {
// TODO(soheil): Maybe sleep instead of busy polling.
gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC);
gpr_timespec delta = gpr_time_sub(now, start);
loop_ns = delta.tv_sec * GPR_NS_PER_SEC + delta.tv_nsec;
} while (loop_ns < measurement_ns);
gpr_cycle_counter end_cycle = gpr_get_cycle_counter();
// Frequency should be in Hz.
const double freq =
static_cast<double>(end_cycle - start_cycle) / loop_ns * GPR_NS_PER_SEC;
converged =
last_freq != -1 && (freq * 0.99 < last_freq && last_freq < freq * 1.01);
last_freq = freq;
}
cycles_per_second = last_freq;
gpr_log(GPR_DEBUG, "... cycles_per_second = %f\n", cycles_per_second);
}
gpr_timespec gpr_cycle_counter_to_time(gpr_cycle_counter cycles) {
const double secs =
static_cast<double>(cycles - start_cycle) / cycles_per_second;
gpr_timespec ts;
ts.tv_sec = static_cast<int64_t>(secs);
ts.tv_nsec = static_cast<int32_t>(GPR_NS_PER_SEC *
(secs - static_cast<double>(ts.tv_sec)));
ts.clock_type = GPR_CLOCK_PRECISE;
return ts;
}
gpr_timespec gpr_cycle_counter_sub(gpr_cycle_counter a, gpr_cycle_counter b) {
const double secs = static_cast<double>(a - b) / cycles_per_second;
gpr_timespec ts;
ts.tv_sec = static_cast<int64_t>(secs);
ts.tv_nsec = static_cast<int32_t>(GPR_NS_PER_SEC *
(secs - static_cast<double>(ts.tv_sec)));
ts.clock_type = GPR_TIMESPAN;
return ts;
}
void gpr_precise_clock_now(gpr_timespec* clk) {
int64_t counter = gpr_get_cycle_counter();
*clk = gpr_cycle_counter_to_time(counter);
}
#elif GPR_CYCLE_COUNTER_FALLBACK
void gpr_precise_clock_init(void) {}
gpr_cycle_counter gpr_get_cycle_counter() {
gpr_timespec ts = gpr_now(GPR_CLOCK_REALTIME);
return gpr_timespec_to_micros(ts);
}
gpr_timespec gpr_cycle_counter_to_time(gpr_cycle_counter cycles) {
gpr_timespec ts;
ts.tv_sec = static_cast<int64_t>(cycles / GPR_US_PER_SEC);
ts.tv_nsec = static_cast<int64_t>((cycles - ts.tv_sec * GPR_US_PER_SEC) *
GPR_NS_PER_US);
ts.clock_type = GPR_CLOCK_PRECISE;
return ts;
}
void gpr_precise_clock_now(gpr_timespec* clk) {
*clk = gpr_now(GPR_CLOCK_REALTIME);
clk->clock_type = GPR_CLOCK_PRECISE;
}
gpr_timespec gpr_cycle_counter_sub(gpr_cycle_counter a, gpr_cycle_counter b) {
return gpr_time_sub(gpr_cycle_counter_to_time(a),
gpr_cycle_counter_to_time(b));
}
#endif // GPR_CYCLE_COUNTER_FALLBACK
#endif // !GPR_CYCLE_COUNTER_CUSTOM
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