Commit a4feb694 authored by Teng Qin's avatar Teng Qin

Perf event example using C++ API

parent dfd9c63b
......@@ -22,3 +22,7 @@ install (TARGETS TCPSendStack DESTINATION share/bcc/examples/cpp)
add_executable(RandomRead RandomRead.cc)
target_link_libraries(RandomRead bcc-static)
install (TARGETS RandomRead DESTINATION share/bcc/examples/cpp)
add_executable(LLCStat LLCStat.cc)
target_link_libraries(LLCStat bcc-static)
install (TARGETS LLCStat DESTINATION share/bcc/examples/cpp)
/*
* LLCStat Show LLC hit ratio for each process on each CPU core.
* For Linux, uses BCC, eBPF. Embedded C.
*
* Basic example of BCC timed sampling perf event.
*
* USAGE: LLCStat [duration]
*
* Copyright (c) Facebook, Inc.
* Licensed under the Apache License, Version 2.0 (the "License")
*/
#include <linux/perf_event.h>
#include <unistd.h>
#include <iomanip>
#include <iostream>
#include <string>
#include "BPF.h"
const std::string BPF_PROGRAM = R"(
#include <linux/ptrace.h>
#include <uapi/linux/bpf_perf_event.h>
struct event_t {
int cpu;
int pid;
char name[16];
};
BPF_HASH(ref_count, struct event_t);
BPF_HASH(miss_count, struct event_t);
static inline __attribute__((always_inline)) void get_key(struct event_t* key) {
key->cpu = bpf_get_smp_processor_id();
key->pid = bpf_get_current_pid_tgid();
bpf_get_current_comm(&(key->name), sizeof(key->name));
}
int on_cache_miss(struct bpf_perf_event_data *ctx) {
struct event_t key = {};
get_key(&key);
u64 zero = 0, *val;
val = miss_count.lookup_or_init(&key, &zero);
(*val) += ctx->sample_period;
return 0;
}
int on_cache_ref(struct bpf_perf_event_data *ctx) {
struct event_t key = {};
get_key(&key);
u64 zero = 0, *val;
val = ref_count.lookup_or_init(&key, &zero);
(*val) += ctx->sample_period;
return 0;
}
)";
struct event_t {
int cpu;
int pid;
char name[16];
};
int main(int argc, char** argv) {
ebpf::BPF bpf;
auto init_res = bpf.init(BPF_PROGRAM);
if (init_res.code() != 0) {
std::cerr << init_res.msg() << std::endl;
return 1;
}
auto attach_ref_res =
bpf.attach_perf_event(PERF_TYPE_HARDWARE, PERF_COUNT_HW_CACHE_REFERENCES,
"on_cache_ref", 100, 0);
if (attach_ref_res.code() != 0) {
std::cerr << attach_ref_res.msg() << std::endl;
return 1;
}
auto attach_miss_res = bpf.attach_perf_event(
PERF_TYPE_HARDWARE, PERF_COUNT_HW_CACHE_MISSES, "on_cache_miss", 100, 0);
if (attach_miss_res.code() != 0) {
std::cerr << attach_miss_res.msg() << std::endl;
return 1;
}
int probe_time = 10;
if (argc == 2) {
probe_time = atoi(argv[1]);
}
std::cout << "Probing for " << probe_time << " seconds" << std::endl;
sleep(probe_time);
bpf.detach_perf_event(PERF_TYPE_HARDWARE, PERF_COUNT_HW_CACHE_REFERENCES);
bpf.detach_perf_event(PERF_TYPE_HARDWARE, PERF_COUNT_HW_CACHE_MISSES);
auto refs = bpf.get_hash_table<event_t, uint64_t>("ref_count");
auto misses = bpf.get_hash_table<event_t, uint64_t>("miss_count");
for (auto it : refs.get_table_offline()) {
uint64_t hit;
try {
auto miss = misses[it.first];
hit = miss <= it.second ? it.second - miss : 0;
} catch (...) {
hit = it.second;
}
double ratio = (double(hit) / double(it.second)) * 100.0;
std::cout << "PID " << std::setw(8) << std::setfill(' ') << it.first.pid;
std::cout << std::setw(20) << std::setfill(' ') << std::left
<< " (" + std::string(it.first.name) + ") " << std::right;
std::cout << "on CPU " << std::setw(2) << std::setfill(' ') << it.first.cpu;
std::cout << " Hit Rate " << std::setprecision(4) << ratio << "% ";
std::cout << "(" << hit << "/" << it.second << ")" << std::endl;
}
return 0;
}
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