simpleperf/cmd_monitor.cpp - platform/system/extras - Git at Google

 /*
  * Copyright (C) 2020 The Android Open Source Project
  *
  * 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 <inttypes.h>
 #include <libgen.h>
 #include <signal.h>
 #include <sys/mman.h>
 #include <sys/prctl.h>
 #include <sys/utsname.h>
 #include <time.h>
 #include <unistd.h>
 #include <optional>
 #include <set>
 #include <string>
 #include <unordered_map>
 #include <unordered_set>
 #include <vector>

 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/parseint.h>
 #include <android-base/stringprintf.h>
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 #if defined(__ANDROID__)
 #include <android-base/properties.h>
 #endif

 #include "IOEventLoop.h"
 #include "MapRecordReader.h"
 #include "OfflineUnwinder.h"
 #include "RecordFilter.h"
 #include "command.h"
 #include "dso.h"
 #include "environment.h"
 #include "event_selection_set.h"
 #include "event_type.h"
 #include "read_elf.h"
 #include "read_symbol_map.h"
 #include "record.h"
 #include "thread_tree.h"
 #include "tracing.h"
 #include "utils.h"

 namespace simpleperf {
 namespace {

 using android::base::ParseUint;
 using android::base::Realpath;
 using android::base::StringAppendF;

 struct SymbolInfo {
   Dso* dso;
   const Symbol* symbol;
   uint64_t vaddr_in_file;
 };

 // The max size of records dumped by kernel is 65535, and dump stack size
 // should be a multiply of 8, so MAX_DUMP_STACK_SIZE is 65528.
 constexpr uint32_t MAX_DUMP_STACK_SIZE = 65528;

 // The max allowed pages in mapped buffer is decided by rlimit(RLIMIT_MEMLOCK).
 // Here 1024 is a desired value for pages in mapped buffer. If mapped
 // successfully, the buffer size = 1024 * 4K (page size) = 4M.
 constexpr size_t DESIRED_PAGES_IN_MAPPED_BUFFER = 1024;

 // Currently, the record buffer size in user-space is set to match the kernel
 // buffer size on a 8 core system. For system-wide recording, it is 8K pages *
 // 4K page_size * 8 cores = 256MB. For non system-wide recording, it is 1K pages
 // * 4K page_size * 8 cores = 64MB.
 static constexpr size_t kRecordBufferSize = 64 * kMegabyte;
 static constexpr size_t kSystemWideRecordBufferSize = 256 * kMegabyte;

 class MonitorCommand : public Command {
  public:
   MonitorCommand()
       : Command(
             "monitor", "monitor events and print their textual representations to stdout",
             // clang-format off
 "Usage: simpleperf monitor [options]\n"
 "       Gather sampling information and print the events on stdout.\n"
 "       For precise recording, prefer the record command.\n"
 "       Currently, only supports system-wide collection.\n"
 "\n"
 "Select monitored threads:\n"
 "-a               System-wide collection. Use with --exclude-perf to exclude\n"
 "                 samples for simpleperf process.\n"
 "\n"
 "Select monitored event types:\n"
 "-e event1[:modifier1],event2[:modifier2],...\n"
 "             Select a list of events to record. An event can be:\n"
 "               1) an event name listed in `simpleperf list`;\n"
 "               2) a raw PMU event in rN format. N is a hex number.\n"
 "                  For example, r1b selects event number 0x1b.\n"
 "             Modifiers can be added to define how the event should be\n"
 "             monitored. Possible modifiers are:\n"
 "                u - monitor user space events only\n"
 "                k - monitor kernel space events only\n"
 "\n"
 "Select monitoring options:\n"
 "-f freq      Set event sample frequency. It means recording at most [freq]\n"
 "             samples every second. For non-tracepoint events, the default\n"
 "             option is -f 4000. A -f/-c option affects all event types\n"
 "             following it until meeting another -f/-c option. For example,\n"
 "             for \"-f 1000 -e cpu-cycles -c 1 -e sched:sched_switch\", cpu-cycles\n"
 "             has sample freq 1000, sched:sched_switch event has sample period 1.\n"
 "-c count     Set event sample period. It means recording one sample when\n"
 "             [count] events happen. For tracepoint events, the default option\n"
 "             is -c 1.\n"
 "--call-graph fp | dwarf[,<dump_stack_size>]\n"
 "             Enable call graph recording. Use frame pointer or dwarf debug\n"
 "             frame as the method to parse call graph in stack.\n"
 "             Default is dwarf,65528.\n"
 "-g           Same as '--call-graph dwarf'.\n"
 "--duration time_in_sec  Monitor for time_in_sec seconds. Here time_in_sec"
 "                        may be any positive floating point number.\n"
 "--cpu-percent <percent>  Set the max percent of cpu time used for recording.\n"
 "                         percent is in range [1-100], default is 25.\n"
 "\n"
 "Sample filter options:\n"
 "--exclude-perf                Exclude samples for simpleperf process.\n"
 RECORD_FILTER_OPTION_HELP_MSG_FOR_RECORDING
 "\n"
             // clang-format on
             ),
         system_wide_collection_(false),
         fp_callchain_sampling_(false),
         dwarf_callchain_sampling_(false),
         dump_stack_size_in_dwarf_sampling_(MAX_DUMP_STACK_SIZE),
         unwind_dwarf_callchain_(true),
         duration_in_sec_(0),
         event_selection_set_(false),
         mmap_page_range_(std::make_pair(1, DESIRED_PAGES_IN_MAPPED_BUFFER)),
         sample_record_count_(0),
         last_record_timestamp_(0u),
         record_filter_(thread_tree_) {
     // If we run `adb shell simpleperf record xxx` and stop profiling by ctrl-c,
     // adb closes sockets connecting simpleperf. After that, simpleperf will
     // receive SIGPIPE when writing to stdout/stderr, which is a problem when we
     // use '--app' option. So ignore SIGPIPE to finish properly.
     signal(SIGPIPE, SIG_IGN);
   }

   bool Run(const std::vector<std::string>& args);

  private:
   bool ParseOptions(const std::vector<std::string>& args);
   bool AdjustPerfEventLimit();
   bool PrepareMonitoring();
   bool DoMonitoring();
   bool SetEventSelectionFlags();
   bool DumpProcessMaps(pid_t pid, const std::unordered_set<pid_t>& tids);
   void DumpSampleRecord(const SampleRecord& sr);
   void DumpSampleCallchain(const SampleRecord& sr);
   bool ProcessRecord(Record* record);
   SymbolInfo GetSymbolInfo(uint32_t pid, uint32_t tid, uint64_t ip, bool in_kernel);
   bool DumpMapsForRecord(Record* record);
   void UpdateRecord(Record* record);
   bool UnwindRecord(SampleRecord& r);

   uint64_t max_sample_freq_ = DEFAULT_SAMPLE_FREQ_FOR_NONTRACEPOINT_EVENT;
   size_t cpu_time_max_percent_ = 25;

   bool system_wide_collection_;
   bool fp_callchain_sampling_;
   bool dwarf_callchain_sampling_;
   uint32_t dump_stack_size_in_dwarf_sampling_;
   bool unwind_dwarf_callchain_;
   std::unique_ptr<OfflineUnwinder> offline_unwinder_;
   double duration_in_sec_;
   EventSelectionSet event_selection_set_;
   std::pair<size_t, size_t> mmap_page_range_;
   ThreadTree thread_tree_;
   uint64_t sample_record_count_;
   uint64_t last_record_timestamp_;  // used to insert Mmap2Records for JIT debug info
   // In system wide recording, record if we have dumped map info for a process.
   std::unordered_set<pid_t> dumped_processes_;
   bool exclude_perf_ = false;
   RecordFilter record_filter_;
   std::unordered_map<uint64_t, std::string> event_names_;

   std::optional<MapRecordReader> map_record_reader_;
 };

 bool MonitorCommand::Run(const std::vector<std::string>& args) {
   ScopedCurrentArch scoped_arch(GetMachineArch());
   if (!CheckPerfEventLimit()) {
     return false;
   }
   AllowMoreOpenedFiles();

   if (!ParseOptions(args)) {
     return false;
   }
   if (!AdjustPerfEventLimit()) {
     return false;
   }

   if (!PrepareMonitoring()) {
     return false;
   }
   return DoMonitoring();
 }

 bool MonitorCommand::PrepareMonitoring() {
   // 1. Process options before opening perf event files.
   if (!SetEventSelectionFlags()) {
     return false;
   }
   if (unwind_dwarf_callchain_) {
     offline_unwinder_ = OfflineUnwinder::Create(false);
   }

   // 2. Add monitored targets.
   if (system_wide_collection_) {
     event_selection_set_.AddMonitoredThreads({-1});
   } else {
     LOG(ERROR) << "No threads to monitor. Try `simpleperf help monitor` for help";
     return false;
   }

   // 3. Open perf event files and create mapped buffers.
   if (!event_selection_set_.OpenEventFiles()) {
     return false;
   }
   size_t record_buffer_size =
       system_wide_collection_ ? kSystemWideRecordBufferSize : kRecordBufferSize;
   if (!event_selection_set_.MmapEventFiles(mmap_page_range_.first, mmap_page_range_.second,
                                            0 /* aux_buffer_size */, record_buffer_size,
                                            false /* allow_truncating_samples */, exclude_perf_)) {
     return false;
   }
   auto callback = std::bind(&MonitorCommand::ProcessRecord, this, std::placeholders::_1);
   if (!event_selection_set_.PrepareToReadMmapEventData(callback)) {
     return false;
   }

   // Keep track of the event names per id.
   event_names_ = event_selection_set_.GetEventNamesById();

   // Use first perf_event_attr and first event id to dump mmap and comm records.
   EventAttrWithId dumping_attr_id = event_selection_set_.GetEventAttrWithId()[0];
   map_record_reader_.emplace(dumping_attr_id.attr, dumping_attr_id.ids[0],
                              event_selection_set_.RecordNotExecutableMaps());
   map_record_reader_->SetCallback([this](Record* r) { return ProcessRecord(r); });

   // 4. Load kallsyms, if possible.
   std::string kallsyms;
   if (LoadKernelSymbols(&kallsyms)) {
     Dso::SetKallsyms(std::move(kallsyms));
   }
   map_record_reader_->ReadKernelMaps();

   // 5. Add read/signal/periodic Events.
   IOEventLoop* loop = event_selection_set_.GetIOEventLoop();
   auto exit_loop_callback = [loop]() { return loop->ExitLoop(); };
   if (!loop->AddSignalEvents({SIGCHLD, SIGINT, SIGTERM}, exit_loop_callback, IOEventHighPriority)) {
     return false;
   }

   // Only add an event for SIGHUP if we didn't inherit SIG_IGN (e.g. from
   // nohup).
   if (!SignalIsIgnored(SIGHUP)) {
     if (!loop->AddSignalEvent(SIGHUP, exit_loop_callback, IOEventHighPriority)) {
       return false;
     }
   }

   if (duration_in_sec_ != 0) {
     if (!loop->AddPeriodicEvent(
             SecondToTimeval(duration_in_sec_), [loop]() { return loop->ExitLoop(); },
             IOEventHighPriority)) {
       return false;
     }
   }
   return true;
 }

 bool MonitorCommand::DoMonitoring() {
   if (!event_selection_set_.GetIOEventLoop()->RunLoop()) {
     return false;
   }
   if (!event_selection_set_.SyncKernelBuffer()) {
     return false;
   }
   event_selection_set_.CloseEventFiles();
   if (!event_selection_set_.FinishReadMmapEventData()) {
     return false;
   }
   LOG(ERROR) << "Processed samples: " << sample_record_count_;
   return true;
 }

 inline const OptionFormatMap& GetMonitorCmdOptionFormats() {
   static OptionFormatMap option_formats;
   if (option_formats.empty()) {
     option_formats = {
         {"-a", {OptionValueType::NONE, OptionType::SINGLE, AppRunnerType::NOT_ALLOWED}},
         {"-c", {OptionValueType::UINT, OptionType::ORDERED, AppRunnerType::ALLOWED}},
         {"--call-graph", {OptionValueType::STRING, OptionType::ORDERED, AppRunnerType::ALLOWED}},
         {"--cpu-percent", {OptionValueType::UINT, OptionType::SINGLE, AppRunnerType::ALLOWED}},
         {"--duration", {OptionValueType::DOUBLE, OptionType::SINGLE, AppRunnerType::ALLOWED}},
         {"-e", {OptionValueType::STRING, OptionType::ORDERED, AppRunnerType::ALLOWED}},
         {"--exclude-perf", {OptionValueType::NONE, OptionType::SINGLE, AppRunnerType::ALLOWED}},
         {"-f", {OptionValueType::UINT, OptionType::ORDERED, AppRunnerType::ALLOWED}},
         {"-g", {OptionValueType::NONE, OptionType::ORDERED, AppRunnerType::ALLOWED}},
         {"-t", {OptionValueType::STRING, OptionType::MULTIPLE, AppRunnerType::ALLOWED}},
     };
     OptionFormatMap record_filter_options = GetRecordFilterOptionFormats(true);
     option_formats.insert(record_filter_options.begin(), record_filter_options.end());
   }
   return option_formats;
 }

 bool MonitorCommand::ParseOptions(const std::vector<std::string>& args) {
   OptionValueMap options;
   std::vector<std::pair<OptionName, OptionValue>> ordered_options;

   if (!PreprocessOptions(args, GetMonitorCmdOptionFormats(), &options, &ordered_options, nullptr)) {
     return false;
   }

   // Process options.
   system_wide_collection_ = options.PullBoolValue("-a");

   if (!options.PullUintValue("--cpu-percent", &cpu_time_max_percent_, 1, 100)) {
     return false;
   }

   if (!options.PullDoubleValue("--duration", &duration_in_sec_, 1e-9)) {
     return false;
   }

   exclude_perf_ = options.PullBoolValue("--exclude-perf");
   if (!record_filter_.ParseOptions(options)) {
     return false;
   }

   CHECK(options.values.empty());

   // Process ordered options.
   for (const auto& pair : ordered_options) {
     const OptionName& name = pair.first;
     const OptionValue& value = pair.second;

     if (name == "-c" || name == "-f") {
       if (value.uint_value < 1) {
         LOG(ERROR) << "invalid " << name << ": " << value.uint_value;
         return false;
       }
       SampleRate rate;
       if (name == "-c") {
         rate.sample_period = value.uint_value;
       } else {
         if (value.uint_value >= INT_MAX) {
           LOG(ERROR) << "sample freq can't be bigger than INT_MAX: " << value.uint_value;
           return false;
         }
         rate.sample_freq = value.uint_value;
       }
       event_selection_set_.SetSampleRateForNewEvents(rate);

     } else if (name == "--call-graph") {
       std::vector<std::string> strs = android::base::Split(value.str_value, ",");
       if (strs[0] == "fp") {
         fp_callchain_sampling_ = true;
         dwarf_callchain_sampling_ = false;
       } else if (strs[0] == "dwarf") {
         fp_callchain_sampling_ = false;
         dwarf_callchain_sampling_ = true;
         if (strs.size() > 1) {
           uint64_t size;
           if (!ParseUint(strs[1], &size)) {
             LOG(ERROR) << "invalid dump stack size in --call-graph option: " << strs[1];
             return false;
           }
           if ((size & 7) != 0) {
             LOG(ERROR) << "dump stack size " << size << " is not 8-byte aligned.";
             return false;
           }
           if (size >= MAX_DUMP_STACK_SIZE) {
             LOG(ERROR) << "dump stack size " << size << " is bigger than max allowed size "
                        << MAX_DUMP_STACK_SIZE << ".";
             return false;
           }
           dump_stack_size_in_dwarf_sampling_ = static_cast<uint32_t>(size);
         }
       }

     } else if (name == "-e") {
       std::vector<std::string> event_types = android::base::Split(value.str_value, ",");
       for (auto& event_type : event_types) {
         if (!event_selection_set_.AddEventType(event_type)) {
           return false;
         }
       }

     } else if (name == "-g") {
       fp_callchain_sampling_ = false;
       dwarf_callchain_sampling_ = true;
     } else {
       CHECK(false) << "unprocessed option: " << name;
     }
   }

   if (event_selection_set_.empty()) {
     LOG(ERROR) << "No event to record. Use `-e` to specify which event should be monitored.";
     return false;
   }

   if (fp_callchain_sampling_) {
     if (GetTargetArch() == ARCH_ARM) {
       LOG(WARNING) << "`--callgraph fp` option doesn't work well on arm architecture, "
                    << "consider using `-g` option or profiling on aarch64 architecture.";
     }
   }

   if (system_wide_collection_ && event_selection_set_.HasMonitoredTarget()) {
     LOG(ERROR) << "Record system wide and existing processes/threads can't be "
                   "used at the same time.";
     return false;
   }

   if (system_wide_collection_ && !IsRoot()) {
     LOG(ERROR) << "System wide profiling needs root privilege.";
     return false;
   }
   return true;
 }

 bool MonitorCommand::AdjustPerfEventLimit() {
   bool set_prop = false;
   // 1. Adjust max_sample_rate.
   uint64_t cur_max_freq;
   if (GetMaxSampleFrequency(&cur_max_freq) && cur_max_freq < max_sample_freq_ &&
       !SetMaxSampleFrequency(max_sample_freq_)) {
     set_prop = true;
   }
   // 2. Adjust perf_cpu_time_max_percent.
   size_t cur_percent;
   if (GetCpuTimeMaxPercent(&cur_percent) && cur_percent != cpu_time_max_percent_ &&
       !SetCpuTimeMaxPercent(cpu_time_max_percent_)) {
     set_prop = true;
   }
   // 3. Adjust perf_event_mlock_kb.
   long cpus = sysconf(_SC_NPROCESSORS_CONF);
   uint64_t mlock_kb = cpus * (mmap_page_range_.second + 1) * 4;

   uint64_t cur_mlock_kb;
   if (GetPerfEventMlockKb(&cur_mlock_kb) && cur_mlock_kb < mlock_kb &&
       !SetPerfEventMlockKb(mlock_kb)) {
     set_prop = true;
   }

   if (GetAndroidVersion() >= kAndroidVersionQ && set_prop) {
     return SetPerfEventLimits(std::max(max_sample_freq_, cur_max_freq), cpu_time_max_percent_,
                               std::max(mlock_kb, cur_mlock_kb));
   }
   return true;
 }

 bool MonitorCommand::SetEventSelectionFlags() {
   event_selection_set_.SampleIdAll();
   event_selection_set_.WakeupPerSample();
   if (fp_callchain_sampling_) {
     event_selection_set_.EnableFpCallChainSampling();
   } else if (dwarf_callchain_sampling_) {
     if (!event_selection_set_.EnableDwarfCallChainSampling(dump_stack_size_in_dwarf_sampling_)) {
       return false;
     }
   }
   return true;
 }

 bool MonitorCommand::ProcessRecord(Record* record) {
   UpdateRecord(record);
   last_record_timestamp_ = std::max(last_record_timestamp_, record->Timestamp());
   // In system wide recording, maps are dumped when they are needed by records.
   if (system_wide_collection_ && !DumpMapsForRecord(record)) {
     return false;
   }
   if (record->type() == PERF_RECORD_SAMPLE) {
     auto& r = *static_cast<SampleRecord*>(record);

     // Record filter check should go after DumpMapsForRecord(). Otherwise, process/thread name
     // filters don't work in system wide collection.
     if (!record_filter_.Check(r)) {
       return true;
     }

     // AdjustCallChainGeneratedByKernel() should go before UnwindRecord().
     // Because we don't want to adjust callchains generated by dwarf unwinder.
     if (fp_callchain_sampling_ || dwarf_callchain_sampling_) {
       r.AdjustCallChainGeneratedByKernel();
       if (!UnwindRecord(r)) {
         return false;
       }
     }
     DumpSampleRecord(r);
     if (fp_callchain_sampling_ || dwarf_callchain_sampling_) {
       DumpSampleCallchain(r);
     }
     sample_record_count_++;
   } else {
     // Other types of record are forwarded to the thread tree to build the
     // representation of each processes (mmap, comm, etc).
     thread_tree_.Update(*record);
   }
   return true;
 }

 void MonitorCommand::DumpSampleRecord(const SampleRecord& sr) {
   std::string output("sample");
   StringAppendF(&output, " name=%s", event_names_[sr.id_data.id].c_str());
   StringAppendF(&output, " ip=%p", reinterpret_cast<void*>(sr.ip_data.ip));
   SymbolInfo s = GetSymbolInfo(sr.tid_data.pid, sr.tid_data.tid, sr.ip_data.ip, sr.InKernel());
   StringAppendF(&output, " symbol=%s (%s[+%" PRIx64 "])", s.symbol->DemangledName(),
                 s.dso->Path().c_str(), s.vaddr_in_file);
   StringAppendF(&output, " pid=%u tid=%u", sr.tid_data.pid, sr.tid_data.tid);
   StringAppendF(&output, " cpu=%u", sr.cpu_data.cpu);
   printf("%s\n", output.c_str());
   fflush(stdout);
 }

 void MonitorCommand::DumpSampleCallchain(const SampleRecord& sr) {
   bool in_kernel = sr.InKernel();
   if (sr.sample_type & PERF_SAMPLE_CALLCHAIN) {
     for (size_t i = 0; i < sr.callchain_data.ip_nr; ++i) {
       if (sr.callchain_data.ips[i] >= PERF_CONTEXT_MAX) {
         if (sr.callchain_data.ips[i] == PERF_CONTEXT_USER) {
           in_kernel = false;
         }
         continue;
       }
       SymbolInfo s =
           GetSymbolInfo(sr.tid_data.pid, sr.tid_data.tid, sr.callchain_data.ips[i], in_kernel);
       std::string output("sample callchain");
       StringAppendF(&output, " %s (%s[+%" PRIx64 "])", s.symbol->DemangledName(),
                     s.dso->Path().c_str(), s.vaddr_in_file);
       printf("%s\n", output.c_str());
     }
     fflush(stdout);
   }
 }

 SymbolInfo MonitorCommand::GetSymbolInfo(uint32_t pid, uint32_t tid, uint64_t ip, bool in_kernel) {
   ThreadEntry* thread = thread_tree_.FindThreadOrNew(pid, tid);
   const MapEntry* map = thread_tree_.FindMap(thread, ip, in_kernel);
   SymbolInfo info;
   info.symbol = thread_tree_.FindSymbol(map, ip, &info.vaddr_in_file, &info.dso);
   return info;
 }

 bool MonitorCommand::DumpMapsForRecord(Record* record) {
   if (record->type() == PERF_RECORD_SAMPLE) {
     pid_t pid = static_cast<SampleRecord*>(record)->tid_data.pid;
     if (dumped_processes_.find(pid) == dumped_processes_.end()) {
       // Dump map info and all thread names for that process.
       if (!map_record_reader_->ReadProcessMaps(pid, last_record_timestamp_)) {
         return false;
       }
       dumped_processes_.insert(pid);
     }
   }
   return true;
 }

 void MonitorCommand::UpdateRecord(Record* record) {
   if (record->type() == PERF_RECORD_COMM) {
     auto r = static_cast<CommRecord*>(record);
     if (r->data->pid == r->data->tid) {
       std::string s = GetCompleteProcessName(r->data->pid);
       if (!s.empty()) {
         r->SetCommandName(s);
       }
     }
   }
 }

 bool MonitorCommand::UnwindRecord(SampleRecord& r) {
   if ((r.sample_type & PERF_SAMPLE_CALLCHAIN) && (r.sample_type & PERF_SAMPLE_REGS_USER) &&
       (r.regs_user_data.reg_mask != 0) && (r.sample_type & PERF_SAMPLE_STACK_USER) &&
       (r.GetValidStackSize() > 0)) {
     ThreadEntry* thread = thread_tree_.FindThreadOrNew(r.tid_data.pid, r.tid_data.tid);
     RegSet regs(r.regs_user_data.abi, r.regs_user_data.reg_mask, r.regs_user_data.regs);
     std::vector<uint64_t> ips;
     std::vector<uint64_t> sps;
     if (!offline_unwinder_->UnwindCallChain(*thread, regs, r.stack_user_data.data,
                                             r.GetValidStackSize(), &ips, &sps)) {
       return false;
     }
     r.ReplaceRegAndStackWithCallChain(ips);
   }
   return true;
 }
 }  // namespace

 void RegisterMonitorCommand() {
   RegisterCommand("monitor", [] { return std::unique_ptr<Command>(new MonitorCommand()); });
 }

 }  // namespace simpleperf
	/*
	* Copyright (C) 2020 The Android Open Source Project
	*
	* 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 <inttypes.h>
	#include <libgen.h>
	#include <signal.h>
	#include <sys/mman.h>
	#include <sys/prctl.h>
	#include <sys/utsname.h>
	#include <time.h>
	#include <unistd.h>
	#include <optional>
	#include <set>
	#include <string>
	#include <unordered_map>
	#include <unordered_set>
	#include <vector>

	#include <android-base/file.h>
	#include <android-base/logging.h>
	#include <android-base/parseint.h>
	#include <android-base/stringprintf.h>
	#include <android-base/strings.h>
	#include <android-base/unique_fd.h>
	#if defined(__ANDROID__)
	#include <android-base/properties.h>
	#endif

	#include "IOEventLoop.h"
	#include "MapRecordReader.h"
	#include "OfflineUnwinder.h"
	#include "RecordFilter.h"
	#include "command.h"
	#include "dso.h"
	#include "environment.h"
	#include "event_selection_set.h"
	#include "event_type.h"
	#include "read_elf.h"
	#include "read_symbol_map.h"
	#include "record.h"
	#include "thread_tree.h"
	#include "tracing.h"
	#include "utils.h"

	namespace simpleperf {
	namespace {

	using android::base::ParseUint;
	using android::base::Realpath;
	using android::base::StringAppendF;

	struct SymbolInfo {
	Dso* dso;
	const Symbol* symbol;
	uint64_t vaddr_in_file;
	};

	// The max size of records dumped by kernel is 65535, and dump stack size
	// should be a multiply of 8, so MAX_DUMP_STACK_SIZE is 65528.
	constexpr uint32_t MAX_DUMP_STACK_SIZE = 65528;

	// The max allowed pages in mapped buffer is decided by rlimit(RLIMIT_MEMLOCK).
	// Here 1024 is a desired value for pages in mapped buffer. If mapped
	// successfully, the buffer size = 1024 * 4K (page size) = 4M.
	constexpr size_t DESIRED_PAGES_IN_MAPPED_BUFFER = 1024;

	// Currently, the record buffer size in user-space is set to match the kernel
	// buffer size on a 8 core system. For system-wide recording, it is 8K pages *
	// 4K page_size * 8 cores = 256MB. For non system-wide recording, it is 1K pages
	// * 4K page_size * 8 cores = 64MB.
	static constexpr size_t kRecordBufferSize = 64 * kMegabyte;
	static constexpr size_t kSystemWideRecordBufferSize = 256 * kMegabyte;

	class MonitorCommand : public Command {
	public:
	MonitorCommand()
	: Command(
	"monitor", "monitor events and print their textual representations to stdout",
	// clang-format off
	"Usage: simpleperf monitor [options]\n"
	" Gather sampling information and print the events on stdout.\n"
	" For precise recording, prefer the record command.\n"
	" Currently, only supports system-wide collection.\n"
	"\n"
	"Select monitored threads:\n"
	"-a System-wide collection. Use with --exclude-perf to exclude\n"
	" samples for simpleperf process.\n"
	"\n"
	"Select monitored event types:\n"
	"-e event1[:modifier1],event2[:modifier2],...\n"
	" Select a list of events to record. An event can be:\n"
	" 1) an event name listed in `simpleperf list`;\n"
	" 2) a raw PMU event in rN format. N is a hex number.\n"
	" For example, r1b selects event number 0x1b.\n"
	" Modifiers can be added to define how the event should be\n"
	" monitored. Possible modifiers are:\n"
	" u - monitor user space events only\n"
	" k - monitor kernel space events only\n"
	"\n"
	"Select monitoring options:\n"
	"-f freq Set event sample frequency. It means recording at most [freq]\n"
	" samples every second. For non-tracepoint events, the default\n"
	" option is -f 4000. A -f/-c option affects all event types\n"
	" following it until meeting another -f/-c option. For example,\n"
	" for \"-f 1000 -e cpu-cycles -c 1 -e sched:sched_switch\", cpu-cycles\n"
	" has sample freq 1000, sched:sched_switch event has sample period 1.\n"
	"-c count Set event sample period. It means recording one sample when\n"
	" [count] events happen. For tracepoint events, the default option\n"
	" is -c 1.\n"
	"--call-graph fp \| dwarf[,<dump_stack_size>]\n"
	" Enable call graph recording. Use frame pointer or dwarf debug\n"
	" frame as the method to parse call graph in stack.\n"
	" Default is dwarf,65528.\n"
	"-g Same as '--call-graph dwarf'.\n"
	"--duration time_in_sec Monitor for time_in_sec seconds. Here time_in_sec"
	" may be any positive floating point number.\n"
	"--cpu-percent <percent> Set the max percent of cpu time used for recording.\n"
	" percent is in range [1-100], default is 25.\n"
	"\n"
	"Sample filter options:\n"
	"--exclude-perf Exclude samples for simpleperf process.\n"
	RECORD_FILTER_OPTION_HELP_MSG_FOR_RECORDING
	"\n"
	// clang-format on
	),
	system_wide_collection_(false),
	fp_callchain_sampling_(false),
	dwarf_callchain_sampling_(false),
	dump_stack_size_in_dwarf_sampling_(MAX_DUMP_STACK_SIZE),
	unwind_dwarf_callchain_(true),
	duration_in_sec_(0),
	event_selection_set_(false),
	mmap_page_range_(std::make_pair(1, DESIRED_PAGES_IN_MAPPED_BUFFER)),
	sample_record_count_(0),
	last_record_timestamp_(0u),
	record_filter_(thread_tree_) {
	// If we run `adb shell simpleperf record xxx` and stop profiling by ctrl-c,
	// adb closes sockets connecting simpleperf. After that, simpleperf will
	// receive SIGPIPE when writing to stdout/stderr, which is a problem when we
	// use '--app' option. So ignore SIGPIPE to finish properly.
	signal(SIGPIPE, SIG_IGN);
	}

	bool Run(const std::vector<std::string>& args);

	private:
	bool ParseOptions(const std::vector<std::string>& args);
	bool AdjustPerfEventLimit();
	bool PrepareMonitoring();
	bool DoMonitoring();
	bool SetEventSelectionFlags();
	bool DumpProcessMaps(pid_t pid, const std::unordered_set<pid_t>& tids);
	void DumpSampleRecord(const SampleRecord& sr);
	void DumpSampleCallchain(const SampleRecord& sr);
	bool ProcessRecord(Record* record);
	SymbolInfo GetSymbolInfo(uint32_t pid, uint32_t tid, uint64_t ip, bool in_kernel);
	bool DumpMapsForRecord(Record* record);
	void UpdateRecord(Record* record);
	bool UnwindRecord(SampleRecord& r);

	uint64_t max_sample_freq_ = DEFAULT_SAMPLE_FREQ_FOR_NONTRACEPOINT_EVENT;
	size_t cpu_time_max_percent_ = 25;

	bool system_wide_collection_;
	bool fp_callchain_sampling_;
	bool dwarf_callchain_sampling_;
	uint32_t dump_stack_size_in_dwarf_sampling_;
	bool unwind_dwarf_callchain_;
	std::unique_ptr<OfflineUnwinder> offline_unwinder_;
	double duration_in_sec_;
	EventSelectionSet event_selection_set_;
	std::pair<size_t, size_t> mmap_page_range_;
	ThreadTree thread_tree_;
	uint64_t sample_record_count_;
	uint64_t last_record_timestamp_; // used to insert Mmap2Records for JIT debug info
	// In system wide recording, record if we have dumped map info for a process.
	std::unordered_set<pid_t> dumped_processes_;
	bool exclude_perf_ = false;
	RecordFilter record_filter_;
	std::unordered_map<uint64_t, std::string> event_names_;

	std::optional<MapRecordReader> map_record_reader_;
	};

	bool MonitorCommand::Run(const std::vector<std::string>& args) {
	ScopedCurrentArch scoped_arch(GetMachineArch());
	if (!CheckPerfEventLimit()) {
	return false;
	}
	AllowMoreOpenedFiles();

	if (!ParseOptions(args)) {
	return false;
	}
	if (!AdjustPerfEventLimit()) {
	return false;
	}

	if (!PrepareMonitoring()) {
	return false;
	}
	return DoMonitoring();
	}

	bool MonitorCommand::PrepareMonitoring() {
	// 1. Process options before opening perf event files.
	if (!SetEventSelectionFlags()) {
	return false;
	}
	if (unwind_dwarf_callchain_) {
	offline_unwinder_ = OfflineUnwinder::Create(false);
	}

	// 2. Add monitored targets.
	if (system_wide_collection_) {
	event_selection_set_.AddMonitoredThreads({-1});
	} else {
	LOG(ERROR) << "No threads to monitor. Try `simpleperf help monitor` for help";
	return false;
	}

	// 3. Open perf event files and create mapped buffers.
	if (!event_selection_set_.OpenEventFiles()) {
	return false;
	}
	size_t record_buffer_size =
	system_wide_collection_ ? kSystemWideRecordBufferSize : kRecordBufferSize;
	if (!event_selection_set_.MmapEventFiles(mmap_page_range_.first, mmap_page_range_.second,
	0 /* aux_buffer_size */, record_buffer_size,
	false /* allow_truncating_samples */, exclude_perf_)) {
	return false;
	}
	auto callback = std::bind(&MonitorCommand::ProcessRecord, this, std::placeholders::_1);
	if (!event_selection_set_.PrepareToReadMmapEventData(callback)) {
	return false;
	}

	// Keep track of the event names per id.
	event_names_ = event_selection_set_.GetEventNamesById();

	// Use first perf_event_attr and first event id to dump mmap and comm records.
	EventAttrWithId dumping_attr_id = event_selection_set_.GetEventAttrWithId()[0];
	map_record_reader_.emplace(dumping_attr_id.attr, dumping_attr_id.ids[0],
	event_selection_set_.RecordNotExecutableMaps());
	map_record_reader_->SetCallback([this](Record* r) { return ProcessRecord(r); });

	// 4. Load kallsyms, if possible.
	std::string kallsyms;
	if (LoadKernelSymbols(&kallsyms)) {
	Dso::SetKallsyms(std::move(kallsyms));
	}
	map_record_reader_->ReadKernelMaps();

	// 5. Add read/signal/periodic Events.
	IOEventLoop* loop = event_selection_set_.GetIOEventLoop();
	auto exit_loop_callback = [loop]() { return loop->ExitLoop(); };
	if (!loop->AddSignalEvents({SIGCHLD, SIGINT, SIGTERM}, exit_loop_callback, IOEventHighPriority)) {
	return false;
	}

	// Only add an event for SIGHUP if we didn't inherit SIG_IGN (e.g. from
	// nohup).
	if (!SignalIsIgnored(SIGHUP)) {
	if (!loop->AddSignalEvent(SIGHUP, exit_loop_callback, IOEventHighPriority)) {
	return false;
	}
	}

	if (duration_in_sec_ != 0) {
	if (!loop->AddPeriodicEvent(
	SecondToTimeval(duration_in_sec_), [loop]() { return loop->ExitLoop(); },
	IOEventHighPriority)) {
	return false;
	}
	}
	return true;
	}

	bool MonitorCommand::DoMonitoring() {
	if (!event_selection_set_.GetIOEventLoop()->RunLoop()) {
	return false;
	}
	if (!event_selection_set_.SyncKernelBuffer()) {
	return false;
	}
	event_selection_set_.CloseEventFiles();
	if (!event_selection_set_.FinishReadMmapEventData()) {
	return false;
	}
	LOG(ERROR) << "Processed samples: " << sample_record_count_;
	return true;
	}

	inline const OptionFormatMap& GetMonitorCmdOptionFormats() {
	static OptionFormatMap option_formats;
	if (option_formats.empty()) {
	option_formats = {
	{"-a", {OptionValueType::NONE, OptionType::SINGLE, AppRunnerType::NOT_ALLOWED}},
	{"-c", {OptionValueType::UINT, OptionType::ORDERED, AppRunnerType::ALLOWED}},
	{"--call-graph", {OptionValueType::STRING, OptionType::ORDERED, AppRunnerType::ALLOWED}},
	{"--cpu-percent", {OptionValueType::UINT, OptionType::SINGLE, AppRunnerType::ALLOWED}},
	{"--duration", {OptionValueType::DOUBLE, OptionType::SINGLE, AppRunnerType::ALLOWED}},
	{"-e", {OptionValueType::STRING, OptionType::ORDERED, AppRunnerType::ALLOWED}},
	{"--exclude-perf", {OptionValueType::NONE, OptionType::SINGLE, AppRunnerType::ALLOWED}},
	{"-f", {OptionValueType::UINT, OptionType::ORDERED, AppRunnerType::ALLOWED}},
	{"-g", {OptionValueType::NONE, OptionType::ORDERED, AppRunnerType::ALLOWED}},
	{"-t", {OptionValueType::STRING, OptionType::MULTIPLE, AppRunnerType::ALLOWED}},
	};
	OptionFormatMap record_filter_options = GetRecordFilterOptionFormats(true);
	option_formats.insert(record_filter_options.begin(), record_filter_options.end());
	}
	return option_formats;
	}

	bool MonitorCommand::ParseOptions(const std::vector<std::string>& args) {
	OptionValueMap options;
	std::vector<std::pair<OptionName, OptionValue>> ordered_options;

	if (!PreprocessOptions(args, GetMonitorCmdOptionFormats(), &options, &ordered_options, nullptr)) {
	return false;
	}

	// Process options.
	system_wide_collection_ = options.PullBoolValue("-a");

	if (!options.PullUintValue("--cpu-percent", &cpu_time_max_percent_, 1, 100)) {
	return false;
	}

	if (!options.PullDoubleValue("--duration", &duration_in_sec_, 1e-9)) {
	return false;
	}

	exclude_perf_ = options.PullBoolValue("--exclude-perf");
	if (!record_filter_.ParseOptions(options)) {
	return false;
	}

	CHECK(options.values.empty());

	// Process ordered options.
	for (const auto& pair : ordered_options) {
	const OptionName& name = pair.first;
	const OptionValue& value = pair.second;

	if (name == "-c" \|\| name == "-f") {
	if (value.uint_value < 1) {
	LOG(ERROR) << "invalid " << name << ": " << value.uint_value;
	return false;
	}
	SampleRate rate;
	if (name == "-c") {
	rate.sample_period = value.uint_value;
	} else {
	if (value.uint_value >= INT_MAX) {
	LOG(ERROR) << "sample freq can't be bigger than INT_MAX: " << value.uint_value;
	return false;
	}
	rate.sample_freq = value.uint_value;
	}
	event_selection_set_.SetSampleRateForNewEvents(rate);

	} else if (name == "--call-graph") {
	std::vector<std::string> strs = android::base::Split(value.str_value, ",");
	if (strs[0] == "fp") {
	fp_callchain_sampling_ = true;
	dwarf_callchain_sampling_ = false;
	} else if (strs[0] == "dwarf") {
	fp_callchain_sampling_ = false;
	dwarf_callchain_sampling_ = true;
	if (strs.size() > 1) {
	uint64_t size;
	if (!ParseUint(strs[1], &size)) {
	LOG(ERROR) << "invalid dump stack size in --call-graph option: " << strs[1];
	return false;
	}
	if ((size & 7) != 0) {
	LOG(ERROR) << "dump stack size " << size << " is not 8-byte aligned.";
	return false;
	}
	if (size >= MAX_DUMP_STACK_SIZE) {
	LOG(ERROR) << "dump stack size " << size << " is bigger than max allowed size "
	<< MAX_DUMP_STACK_SIZE << ".";
	return false;
	}
	dump_stack_size_in_dwarf_sampling_ = static_cast<uint32_t>(size);
	}
	}

	} else if (name == "-e") {
	std::vector<std::string> event_types = android::base::Split(value.str_value, ",");
	for (auto& event_type : event_types) {
	if (!event_selection_set_.AddEventType(event_type)) {
	return false;
	}
	}

	} else if (name == "-g") {
	fp_callchain_sampling_ = false;
	dwarf_callchain_sampling_ = true;
	} else {
	CHECK(false) << "unprocessed option: " << name;
	}
	}

	if (event_selection_set_.empty()) {
	LOG(ERROR) << "No event to record. Use `-e` to specify which event should be monitored.";
	return false;
	}

	if (fp_callchain_sampling_) {
	if (GetTargetArch() == ARCH_ARM) {
	LOG(WARNING) << "`--callgraph fp` option doesn't work well on arm architecture, "
	<< "consider using `-g` option or profiling on aarch64 architecture.";
	}
	}

	if (system_wide_collection_ && event_selection_set_.HasMonitoredTarget()) {
	LOG(ERROR) << "Record system wide and existing processes/threads can't be "
	"used at the same time.";
	return false;
	}

	if (system_wide_collection_ && !IsRoot()) {
	LOG(ERROR) << "System wide profiling needs root privilege.";
	return false;
	}
	return true;
	}

	bool MonitorCommand::AdjustPerfEventLimit() {
	bool set_prop = false;
	// 1. Adjust max_sample_rate.
	uint64_t cur_max_freq;
	if (GetMaxSampleFrequency(&cur_max_freq) && cur_max_freq < max_sample_freq_ &&
	!SetMaxSampleFrequency(max_sample_freq_)) {
	set_prop = true;
	}
	// 2. Adjust perf_cpu_time_max_percent.
	size_t cur_percent;
	if (GetCpuTimeMaxPercent(&cur_percent) && cur_percent != cpu_time_max_percent_ &&
	!SetCpuTimeMaxPercent(cpu_time_max_percent_)) {
	set_prop = true;
	}
	// 3. Adjust perf_event_mlock_kb.
	long cpus = sysconf(_SC_NPROCESSORS_CONF);
	uint64_t mlock_kb = cpus * (mmap_page_range_.second + 1) * 4;

	uint64_t cur_mlock_kb;
	if (GetPerfEventMlockKb(&cur_mlock_kb) && cur_mlock_kb < mlock_kb &&
	!SetPerfEventMlockKb(mlock_kb)) {
	set_prop = true;
	}

	if (GetAndroidVersion() >= kAndroidVersionQ && set_prop) {
	return SetPerfEventLimits(std::max(max_sample_freq_, cur_max_freq), cpu_time_max_percent_,
	std::max(mlock_kb, cur_mlock_kb));
	}
	return true;
	}

	bool MonitorCommand::SetEventSelectionFlags() {
	event_selection_set_.SampleIdAll();
	event_selection_set_.WakeupPerSample();
	if (fp_callchain_sampling_) {
	event_selection_set_.EnableFpCallChainSampling();
	} else if (dwarf_callchain_sampling_) {
	if (!event_selection_set_.EnableDwarfCallChainSampling(dump_stack_size_in_dwarf_sampling_)) {
	return false;
	}
	}
	return true;
	}

	bool MonitorCommand::ProcessRecord(Record* record) {
	UpdateRecord(record);
	last_record_timestamp_ = std::max(last_record_timestamp_, record->Timestamp());
	// In system wide recording, maps are dumped when they are needed by records.
	if (system_wide_collection_ && !DumpMapsForRecord(record)) {
	return false;
	}
	if (record->type() == PERF_RECORD_SAMPLE) {
	auto& r = static_cast<SampleRecord>(record);

	// Record filter check should go after DumpMapsForRecord(). Otherwise, process/thread name
	// filters don't work in system wide collection.
	if (!record_filter_.Check(r)) {
	return true;
	}

	// AdjustCallChainGeneratedByKernel() should go before UnwindRecord().
	// Because we don't want to adjust callchains generated by dwarf unwinder.
	if (fp_callchain_sampling_ \|\| dwarf_callchain_sampling_) {
	r.AdjustCallChainGeneratedByKernel();
	if (!UnwindRecord(r)) {
	return false;
	}
	}
	DumpSampleRecord(r);
	if (fp_callchain_sampling_ \|\| dwarf_callchain_sampling_) {
	DumpSampleCallchain(r);
	}
	sample_record_count_++;
	} else {
	// Other types of record are forwarded to the thread tree to build the
	// representation of each processes (mmap, comm, etc).
	thread_tree_.Update(*record);
	}
	return true;
	}

	void MonitorCommand::DumpSampleRecord(const SampleRecord& sr) {
	std::string output("sample");
	StringAppendF(&output, " name=%s", event_names_[sr.id_data.id].c_str());
	StringAppendF(&output, " ip=%p", reinterpret_cast<void*>(sr.ip_data.ip));
	SymbolInfo s = GetSymbolInfo(sr.tid_data.pid, sr.tid_data.tid, sr.ip_data.ip, sr.InKernel());
	StringAppendF(&output, " symbol=%s (%s[+%" PRIx64 "])", s.symbol->DemangledName(),
	s.dso->Path().c_str(), s.vaddr_in_file);
	StringAppendF(&output, " pid=%u tid=%u", sr.tid_data.pid, sr.tid_data.tid);
	StringAppendF(&output, " cpu=%u", sr.cpu_data.cpu);
	printf("%s\n", output.c_str());
	fflush(stdout);
	}

	void MonitorCommand::DumpSampleCallchain(const SampleRecord& sr) {
	bool in_kernel = sr.InKernel();
	if (sr.sample_type & PERF_SAMPLE_CALLCHAIN) {
	for (size_t i = 0; i < sr.callchain_data.ip_nr; ++i) {
	if (sr.callchain_data.ips[i] >= PERF_CONTEXT_MAX) {
	if (sr.callchain_data.ips[i] == PERF_CONTEXT_USER) {
	in_kernel = false;
	}
	continue;
	}
	SymbolInfo s =
	GetSymbolInfo(sr.tid_data.pid, sr.tid_data.tid, sr.callchain_data.ips[i], in_kernel);
	std::string output("sample callchain");
	StringAppendF(&output, " %s (%s[+%" PRIx64 "])", s.symbol->DemangledName(),
	s.dso->Path().c_str(), s.vaddr_in_file);
	printf("%s\n", output.c_str());
	}
	fflush(stdout);
	}
	}

	SymbolInfo MonitorCommand::GetSymbolInfo(uint32_t pid, uint32_t tid, uint64_t ip, bool in_kernel) {
	ThreadEntry* thread = thread_tree_.FindThreadOrNew(pid, tid);
	const MapEntry* map = thread_tree_.FindMap(thread, ip, in_kernel);
	SymbolInfo info;
	info.symbol = thread_tree_.FindSymbol(map, ip, &info.vaddr_in_file, &info.dso);
	return info;
	}

	bool MonitorCommand::DumpMapsForRecord(Record* record) {
	if (record->type() == PERF_RECORD_SAMPLE) {
	pid_t pid = static_cast<SampleRecord*>(record)->tid_data.pid;
	if (dumped_processes_.find(pid) == dumped_processes_.end()) {
	// Dump map info and all thread names for that process.
	if (!map_record_reader_->ReadProcessMaps(pid, last_record_timestamp_)) {
	return false;
	}
	dumped_processes_.insert(pid);
	}
	}
	return true;
	}

	void MonitorCommand::UpdateRecord(Record* record) {
	if (record->type() == PERF_RECORD_COMM) {
	auto r = static_cast<CommRecord*>(record);
	if (r->data->pid == r->data->tid) {
	std::string s = GetCompleteProcessName(r->data->pid);
	if (!s.empty()) {
	r->SetCommandName(s);
	}
	}
	}
	}

	bool MonitorCommand::UnwindRecord(SampleRecord& r) {
	if ((r.sample_type & PERF_SAMPLE_CALLCHAIN) && (r.sample_type & PERF_SAMPLE_REGS_USER) &&
	(r.regs_user_data.reg_mask != 0) && (r.sample_type & PERF_SAMPLE_STACK_USER) &&
	(r.GetValidStackSize() > 0)) {
	ThreadEntry* thread = thread_tree_.FindThreadOrNew(r.tid_data.pid, r.tid_data.tid);
	RegSet regs(r.regs_user_data.abi, r.regs_user_data.reg_mask, r.regs_user_data.regs);
	std::vector<uint64_t> ips;
	std::vector<uint64_t> sps;
	if (!offline_unwinder_->UnwindCallChain(*thread, regs, r.stack_user_data.data,
	r.GetValidStackSize(), &ips, &sps)) {
	return false;
	}
	r.ReplaceRegAndStackWithCallChain(ips);
	}
	return true;
	}
	} // namespace

	void RegisterMonitorCommand() {
	RegisterCommand("monitor", [] { return std::unique_ptr<Command>(new MonitorCommand()); });
	}

	} // namespace simpleperf