1 files changed, 282 insertions, 0 deletions
diff --git a/src/perf_counters.cc b/src/perf_counters.cc
new file mode 100644
index 0000000..417acdb
--- /dev/null
+++ b/src/perf_counters.cc
@@ -0,0 +1,282 @@
+// Copyright 2021 Google Inc. All rights reserved.
+//
+// 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 "perf_counters.h"
+
+#include <cstring>
+#include <memory>
+#include <vector>
+
+#if defined HAVE_LIBPFM
+#include "perfmon/pfmlib.h"
+#include "perfmon/pfmlib_perf_event.h"
+#endif
+
+namespace benchmark {
+namespace internal {
+
+constexpr size_t PerfCounterValues::kMaxCounters;
+
+#if defined HAVE_LIBPFM
+
+size_t PerfCounterValues::Read(const std::vector<int>& leaders) {
+  // Create a pointer for multiple reads
+  const size_t bufsize = values_.size() * sizeof(values_[0]);
+  char* ptr = reinterpret_cast<char*>(values_.data());
+  size_t size = bufsize;
+  for (int lead : leaders) {
+    auto read_bytes = ::read(lead, ptr, size);
+    if (read_bytes >= ssize_t(sizeof(uint64_t))) {
+      // Actual data bytes are all bytes minus initial padding
+      std::size_t data_bytes = read_bytes - sizeof(uint64_t);
+      // This should be very cheap since it's in hot cache
+      std::memmove(ptr, ptr + sizeof(uint64_t), data_bytes);
+      // Increment our counters
+      ptr += data_bytes;
+      size -= data_bytes;
+    } else {
+      int err = errno;
+      GetErrorLogInstance() << "Error reading lead " << lead << " errno:" << err
+                            << " " << ::strerror(err) << "\n";
+      return 0;
+    }
+  }
+  return (bufsize - size) / sizeof(uint64_t);
+}
+
+const bool PerfCounters::kSupported = true;
+
+// Initializes libpfm only on the first call.  Returns whether that single
+// initialization was successful.
+bool PerfCounters::Initialize() {
+  // Function-scope static gets initialized only once on first call.
+  static const bool success = []() {
+    return pfm_initialize() == PFM_SUCCESS;
+  }();
+  return success;
+}
+
+bool PerfCounters::IsCounterSupported(const std::string& name) {
+  Initialize();
+  perf_event_attr_t attr;
+  std::memset(&attr, 0, sizeof(attr));
+  pfm_perf_encode_arg_t arg;
+  std::memset(&arg, 0, sizeof(arg));
+  arg.attr = &attr;
+  const int mode = PFM_PLM3;  // user mode only
+  int ret = pfm_get_os_event_encoding(name.c_str(), mode, PFM_OS_PERF_EVENT_EXT,
+                                      &arg);
+  return (ret == PFM_SUCCESS);
+}
+
+PerfCounters PerfCounters::Create(
+    const std::vector<std::string>& counter_names) {
+  if (!counter_names.empty()) {
+    Initialize();
+  }
+
+  // Valid counters will populate these arrays but we start empty
+  std::vector<std::string> valid_names;
+  std::vector<int> counter_ids;
+  std::vector<int> leader_ids;
+
+  // Resize to the maximum possible
+  valid_names.reserve(counter_names.size());
+  counter_ids.reserve(counter_names.size());
+
+  const int kCounterMode = PFM_PLM3;  // user mode only
+
+  // Group leads will be assigned on demand. The idea is that once we cannot
+  // create a counter descriptor, the reason is that this group has maxed out
+  // so we set the group_id again to -1 and retry - giving the algorithm a
+  // chance to create a new group leader to hold the next set of counters.
+  int group_id = -1;
+
+  // Loop through all performance counters
+  for (size_t i = 0; i < counter_names.size(); ++i) {
+    // we are about to push into the valid names vector
+    // check if we did not reach the maximum
+    if (valid_names.size() == PerfCounterValues::kMaxCounters) {
+      // Log a message if we maxed out and stop adding
+      GetErrorLogInstance()
+          << counter_names.size() << " counters were requested. The maximum is "
+          << PerfCounterValues::kMaxCounters << " and " << valid_names.size()
+          << " were already added. All remaining counters will be ignored\n";
+      // stop the loop and return what we have already
+      break;
+    }
+
+    // Check if this name is empty
+    const auto& name = counter_names[i];
+    if (name.empty()) {
+      GetErrorLogInstance()
+          << "A performance counter name was the empty string\n";
+      continue;
+    }
+
+    // Here first means first in group, ie the group leader
+    const bool is_first = (group_id < 0);
+
+    // This struct will be populated by libpfm from the counter string
+    // and then fed into the syscall perf_event_open
+    struct perf_event_attr attr {};
+    attr.size = sizeof(attr);
+
+    // This is the input struct to libpfm.
+    pfm_perf_encode_arg_t arg{};
+    arg.attr = &attr;
+    const int pfm_get = pfm_get_os_event_encoding(name.c_str(), kCounterMode,
+                                                  PFM_OS_PERF_EVENT, &arg);
+    if (pfm_get != PFM_SUCCESS) {
+      GetErrorLogInstance()
+          << "Unknown performance counter name: " << name << "\n";
+      continue;
+    }
+
+    // We then proceed to populate the remaining fields in our attribute struct
+    // Note: the man page for perf_event_create suggests inherit = true and
+    // read_format = PERF_FORMAT_GROUP don't work together, but that's not the
+    // case.
+    attr.disabled = is_first;
+    attr.inherit = true;
+    attr.pinned = is_first;
+    attr.exclude_kernel = true;
+    attr.exclude_user = false;
+    attr.exclude_hv = true;
+
+    // Read all counters in a group in one read.
+    attr.read_format = PERF_FORMAT_GROUP;
+
+    int id = -1;
+    while (id < 0) {
+      static constexpr size_t kNrOfSyscallRetries = 5;
+      // Retry syscall as it was interrupted often (b/64774091).
+      for (size_t num_retries = 0; num_retries < kNrOfSyscallRetries;
+           ++num_retries) {
+        id = perf_event_open(&attr, 0, -1, group_id, 0);
+        if (id >= 0 || errno != EINTR) {
+          break;
+        }
+      }
+      if (id < 0) {
+        // If the file descriptor is negative we might have reached a limit
+        // in the current group. Set the group_id to -1 and retry
+        if (group_id >= 0) {
+          // Create a new group
+          group_id = -1;
+        } else {
+          // At this point we have already retried to set a new group id and
+          // failed. We then give up.
+          break;
+        }
+      }
+    }
+
+    // We failed to get a new file descriptor. We might have reached a hard
+    // hardware limit that cannot be resolved even with group multiplexing
+    if (id < 0) {
+      GetErrorLogInstance() << "***WARNING** Failed to get a file descriptor "
+                               "for performance counter "
+                            << name << ". Ignoring\n";
+
+      // We give up on this counter but try to keep going
+      // as the others would be fine
+      continue;
+    }
+    if (group_id < 0) {
+      // This is a leader, store and assign it to the current file descriptor
+      leader_ids.push_back(id);
+      group_id = id;
+    }
+    // This is a valid counter, add it to our descriptor's list
+    counter_ids.push_back(id);
+    valid_names.push_back(name);
+  }
+
+  // Loop through all group leaders activating them
+  // There is another option of starting ALL counters in a process but
+  // that would be far reaching an intrusion. If the user is using PMCs
+  // by themselves then this would have a side effect on them. It is
+  // friendlier to loop through all groups individually.
+  for (int lead : leader_ids) {
+    if (ioctl(lead, PERF_EVENT_IOC_ENABLE) != 0) {
+      // This should never happen but if it does, we give up on the
+      // entire batch as recovery would be a mess.
+      GetErrorLogInstance() << "***WARNING*** Failed to start counters. "
+                               "Claring out all counters.\n";
+
+      // Close all peformance counters
+      for (int id : counter_ids) {
+        ::close(id);
+      }
+
+      // Return an empty object so our internal state is still good and
+      // the process can continue normally without impact
+      return NoCounters();
+    }
+  }
+
+  return PerfCounters(std::move(valid_names), std::move(counter_ids),
+                      std::move(leader_ids));
+}
+
+void PerfCounters::CloseCounters() const {
+  if (counter_ids_.empty()) {
+    return;
+  }
+  for (int lead : leader_ids_) {
+    ioctl(lead, PERF_EVENT_IOC_DISABLE);
+  }
+  for (int fd : counter_ids_) {
+    close(fd);
+  }
+}
+#else   // defined HAVE_LIBPFM
+size_t PerfCounterValues::Read(const std::vector<int>&) { return 0; }
+
+const bool PerfCounters::kSupported = false;
+
+bool PerfCounters::Initialize() { return false; }
+
+bool PerfCounters::IsCounterSupported(const std::string&) { return false; }
+
+PerfCounters PerfCounters::Create(
+    const std::vector<std::string>& counter_names) {
+  if (!counter_names.empty()) {
+    GetErrorLogInstance() << "Performance counters not supported.";
+  }
+  return NoCounters();
+}
+
+void PerfCounters::CloseCounters() const {}
+#endif  // defined HAVE_LIBPFM
+
+PerfCountersMeasurement::PerfCountersMeasurement(
+    const std::vector<std::string>& counter_names)
+    : start_values_(counter_names.size()), end_values_(counter_names.size()) {
+  counters_ = PerfCounters::Create(counter_names);
+}
+
+PerfCounters& PerfCounters::operator=(PerfCounters&& other) noexcept {
+  if (this != &other) {
+    CloseCounters();
+
+    counter_ids_ = std::move(other.counter_ids_);
+    leader_ids_ = std::move(other.leader_ids_);
+    counter_names_ = std::move(other.counter_names_);
+  }
+  return *this;
+}
+}  // namespace internal
+}  // namespace benchmark