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Merge #9202: bench: Add support for measuring CPU cycles

3532818 bench: Add support for measuring CPU cycles (Wladimir J. van der Laan)
0.14
Wladimir J. van der Laan 8 years ago
parent
commit
e56cf67e6b
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GPG Key ID: 74810B012346C9A6
  1. 4
      src/Makefile.bench.include
  2. 22
      src/bench/bench.cpp
  3. 10
      src/bench/bench.h
  4. 53
      src/bench/perf.cpp
  5. 37
      src/bench/perf.h

4
src/Makefile.bench.include

@ -22,7 +22,9 @@ bench_bench_bitcoin_SOURCES = \ @@ -22,7 +22,9 @@ bench_bench_bitcoin_SOURCES = \
bench/mempool_eviction.cpp \
bench/verify_script.cpp \
bench/base58.cpp \
bench/lockedpool.cpp
bench/lockedpool.cpp \
bench/perf.cpp \
bench/perf.h
nodist_bench_bench_bitcoin_SOURCES = $(GENERATED_TEST_FILES)

22
src/bench/bench.cpp

@ -3,6 +3,7 @@ @@ -3,6 +3,7 @@
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include "bench.h"
#include "perf.h"
#include <iostream>
#include <iomanip>
@ -26,7 +27,9 @@ BenchRunner::BenchRunner(std::string name, BenchFunction func) @@ -26,7 +27,9 @@ BenchRunner::BenchRunner(std::string name, BenchFunction func)
void
BenchRunner::RunAll(double elapsedTimeForOne)
{
std::cout << "#Benchmark" << "," << "count" << "," << "min" << "," << "max" << "," << "average" << "\n";
perf_init();
std::cout << "#Benchmark" << "," << "count" << "," << "min" << "," << "max" << "," << "average" << ","
<< "min_cycles" << "," << "max_cycles" << "," << "average_cycles" << "\n";
for (std::map<std::string,BenchFunction>::iterator it = benchmarks.begin();
it != benchmarks.end(); ++it) {
@ -35,6 +38,7 @@ BenchRunner::RunAll(double elapsedTimeForOne) @@ -35,6 +38,7 @@ BenchRunner::RunAll(double elapsedTimeForOne)
BenchFunction& func = it->second;
func(state);
}
perf_fini();
}
bool State::KeepRunning()
@ -44,8 +48,10 @@ bool State::KeepRunning() @@ -44,8 +48,10 @@ bool State::KeepRunning()
return true;
}
double now;
uint64_t nowCycles;
if (count == 0) {
lastTime = beginTime = now = gettimedouble();
lastCycles = beginCycles = nowCycles = perf_cpucycles();
}
else {
now = gettimedouble();
@ -53,6 +59,13 @@ bool State::KeepRunning() @@ -53,6 +59,13 @@ bool State::KeepRunning()
double elapsedOne = elapsed * countMaskInv;
if (elapsedOne < minTime) minTime = elapsedOne;
if (elapsedOne > maxTime) maxTime = elapsedOne;
// We only use relative values, so don't have to handle 64-bit wrap-around specially
nowCycles = perf_cpucycles();
uint64_t elapsedOneCycles = (nowCycles - lastCycles) * countMaskInv;
if (elapsedOneCycles < minCycles) minCycles = elapsedOneCycles;
if (elapsedOneCycles > maxCycles) maxCycles = elapsedOneCycles;
if (elapsed*128 < maxElapsed) {
// If the execution was much too fast (1/128th of maxElapsed), increase the count mask by 8x and restart timing.
// The restart avoids including the overhead of this code in the measurement.
@ -61,6 +74,8 @@ bool State::KeepRunning() @@ -61,6 +74,8 @@ bool State::KeepRunning()
count = 0;
minTime = std::numeric_limits<double>::max();
maxTime = std::numeric_limits<double>::min();
minCycles = std::numeric_limits<uint64_t>::max();
maxCycles = std::numeric_limits<uint64_t>::min();
return true;
}
if (elapsed*16 < maxElapsed) {
@ -72,6 +87,7 @@ bool State::KeepRunning() @@ -72,6 +87,7 @@ bool State::KeepRunning()
}
}
lastTime = now;
lastCycles = nowCycles;
++count;
if (now - beginTime < maxElapsed) return true; // Keep going
@ -80,7 +96,9 @@ bool State::KeepRunning() @@ -80,7 +96,9 @@ bool State::KeepRunning()
// Output results
double average = (now-beginTime)/count;
std::cout << std::fixed << std::setprecision(15) << name << "," << count << "," << minTime << "," << maxTime << "," << average << "\n";
int64_t averageCycles = (nowCycles-beginCycles)/count;
std::cout << std::fixed << std::setprecision(15) << name << "," << count << "," << minTime << "," << maxTime << "," << average << ","
<< minCycles << "," << maxCycles << "," << averageCycles << "\n";
return false;
}

10
src/bench/bench.h

@ -41,12 +41,18 @@ namespace benchmark { @@ -41,12 +41,18 @@ namespace benchmark {
double maxElapsed;
double beginTime;
double lastTime, minTime, maxTime, countMaskInv;
int64_t count;
int64_t countMask;
uint64_t count;
uint64_t countMask;
uint64_t beginCycles;
uint64_t lastCycles;
uint64_t minCycles;
uint64_t maxCycles;
public:
State(std::string _name, double _maxElapsed) : name(_name), maxElapsed(_maxElapsed), count(0) {
minTime = std::numeric_limits<double>::max();
maxTime = std::numeric_limits<double>::min();
minCycles = std::numeric_limits<uint64_t>::max();
maxCycles = std::numeric_limits<uint64_t>::min();
countMask = 1;
countMaskInv = 1./(countMask + 1);
}

53
src/bench/perf.cpp

@ -0,0 +1,53 @@ @@ -0,0 +1,53 @@
// Copyright (c) 2016 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include "perf.h"
#if defined(__i386__) || defined(__x86_64__)
/* These architectures support quering the cycle counter
* from user space, no need for any syscall overhead.
*/
void perf_init(void) { }
void perf_fini(void) { }
#elif defined(__linux__)
#include <unistd.h>
#include <sys/syscall.h>
#include <linux/perf_event.h>
static int fd = -1;
static struct perf_event_attr attr;
void perf_init(void)
{
attr.type = PERF_TYPE_HARDWARE;
attr.config = PERF_COUNT_HW_CPU_CYCLES;
fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, 0);
}
void perf_fini(void)
{
if (fd != -1) {
close(fd);
}
}
uint64_t perf_cpucycles(void)
{
uint64_t result = 0;
if (fd == -1 || read(fd, &result, sizeof(result)) < (ssize_t)sizeof(result)) {
return 0;
}
return result;
}
#else /* Unhandled platform */
void perf_init(void) { }
void perf_fini(void) { }
uint64_t perf_cpucycles(void) { return 0; }
#endif

37
src/bench/perf.h

@ -0,0 +1,37 @@ @@ -0,0 +1,37 @@
// Copyright (c) 2016 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
/** Functions for measurement of CPU cycles */
#ifndef H_PERF
#define H_PERF
#include <stdint.h>
#if defined(__i386__)
static inline uint64_t perf_cpucycles(void)
{
uint64_t x;
__asm__ volatile (".byte 0x0f, 0x31" : "=A" (x));
return x;
}
#elif defined(__x86_64__)
static inline uint64_t perf_cpucycles(void)
{
uint32_t hi, lo;
__asm__ __volatile__ ("rdtsc" : "=a"(lo), "=d"(hi));
return ((uint64_t)lo)|(((uint64_t)hi)<<32);
}
#else
uint64_t perf_cpucycles(void);
#endif
void perf_init(void);
void perf_fini(void);
#endif // H_PERF
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