1 // Copyright 2021 Google Inc. All rights reserved.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 //     http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 
15 #include "perf_counters.h"
16 
17 #include <cstring>
18 #include <vector>
19 
20 #if defined HAVE_LIBPFM
21 #include "perfmon/pfmlib.h"
22 #include "perfmon/pfmlib_perf_event.h"
23 #endif
24 
25 namespace benchmark {
26 namespace internal {
27 
28 constexpr size_t PerfCounterValues::kMaxCounters;
29 
30 #if defined HAVE_LIBPFM
31 const bool PerfCounters::kSupported = true;
32 
33 bool PerfCounters::Initialize() { return pfm_initialize() == PFM_SUCCESS; }
34 
35 PerfCounters PerfCounters::Create(
36     const std::vector<std::string>& counter_names) {
37   if (counter_names.empty()) {
38     return NoCounters();
39   }
40   if (counter_names.size() > PerfCounterValues::kMaxCounters) {
41     GetErrorLogInstance()
42         << counter_names.size()
43         << " counters were requested. The minimum is 1, the maximum is "
44         << PerfCounterValues::kMaxCounters << "\n";
45     return NoCounters();
46   }
47   std::vector<int> counter_ids(counter_names.size());
48 
49   const int mode = PFM_PLM3;  // user mode only
50   for (size_t i = 0; i < counter_names.size(); ++i) {
51     const bool is_first = i == 0;
52     struct perf_event_attr attr {};
53     attr.size = sizeof(attr);
54     const int group_id = !is_first ? counter_ids[0] : -1;
55     const auto& name = counter_names[i];
56     if (name.empty()) {
57       GetErrorLogInstance() << "A counter name was the empty string\n";
58       return NoCounters();
59     }
60     pfm_perf_encode_arg_t arg{};
61     arg.attr = &attr;
62 
63     const int pfm_get =
64         pfm_get_os_event_encoding(name.c_str(), mode, PFM_OS_PERF_EVENT, &arg);
65     if (pfm_get != PFM_SUCCESS) {
66       GetErrorLogInstance() << "Unknown counter name: " << name << "\n";
67       return NoCounters();
68     }
69     attr.disabled = is_first;
70     // Note: the man page for perf_event_create suggests inerit = true and
71     // read_format = PERF_FORMAT_GROUP don't work together, but that's not the
72     // case.
73     attr.inherit = true;
74     attr.pinned = is_first;
75     attr.exclude_kernel = true;
76     attr.exclude_user = false;
77     attr.exclude_hv = true;
78     // Read all counters in one read.
79     attr.read_format = PERF_FORMAT_GROUP;
80 
81     int id = -1;
82     static constexpr size_t kNrOfSyscallRetries = 5;
83     // Retry syscall as it was interrupted often (b/64774091).
84     for (size_t num_retries = 0; num_retries < kNrOfSyscallRetries;
85          ++num_retries) {
86       id = perf_event_open(&attr, 0, -1, group_id, 0);
87       if (id >= 0 || errno != EINTR) {
88         break;
89       }
90     }
91     if (id < 0) {
92       GetErrorLogInstance()
93           << "Failed to get a file descriptor for " << name << "\n";
94       return NoCounters();
95     }
96 
97     counter_ids[i] = id;
98   }
99   if (ioctl(counter_ids[0], PERF_EVENT_IOC_ENABLE) != 0) {
100     GetErrorLogInstance() << "Failed to start counters\n";
101     return NoCounters();
102   }
103 
104   return PerfCounters(counter_names, std::move(counter_ids));
105 }
106 
107 PerfCounters::~PerfCounters() {
108   if (counter_ids_.empty()) {
109     return;
110   }
111   ioctl(counter_ids_[0], PERF_EVENT_IOC_DISABLE);
112   for (int fd : counter_ids_) {
113     close(fd);
114   }
115 }
116 #else   // defined HAVE_LIBPFM
117 const bool PerfCounters::kSupported = false;
118 
119 bool PerfCounters::Initialize() { return false; }
120 
121 PerfCounters PerfCounters::Create(
122     const std::vector<std::string>& counter_names) {
123   if (!counter_names.empty()) {
124     GetErrorLogInstance() << "Performance counters not supported.";
125   }
126   return NoCounters();
127 }
128 
129 PerfCounters::~PerfCounters() = default;
130 #endif  // defined HAVE_LIBPFM
131 }  // namespace internal
132 }  // namespace benchmark
133