Perf event example using C++ API

examples/cpp/CMakeLists.txt

@@ -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)

examples/cpp/LLCStat.cc

+/*
+ * 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;
+}