Simpleperf: don't use ioctl(PERF_EVENT_IOC_ENABLE).

Some android kernels(like bullhead/angler) can't handle
ioctl(PERF_EVENT_IOC_ENABLE) correctly when cpu-hotplug
happens. Instead of fixing all of them in kernel, we
can't simply don't use it.

Bug: 25193162
Change-Id: I9df1458045ffd2ccc2c7ba393e746ebba7c253de

simpleperf/cmd_record.cpp

@@ -231,11 +231,6 @@ bool RecordCommand::Run(const std::vector<std::string>& args) {
   }
 
   // 5. Write records in mmap buffers of perf_event_files to output file while workload is running.
-  if (!event_selection_set_.GetEnableOnExec()) {
-    if (!event_selection_set_.EnableEvents()) {
-      return false;
-    }
-  }
   if (workload != nullptr && !workload->Start()) {
     return false;
   }

simpleperf/cmd_stat.cpp

@@ -145,11 +145,6 @@ bool StatCommand::Run(const std::vector<std::string>& args) {
 
   // 4. Count events while workload running.
   auto start_time = std::chrono::steady_clock::now();
-  if (!event_selection_set_.GetEnableOnExec()) {
-    if (!event_selection_set_.EnableEvents()) {
-      return false;
-    }
-  }
   if (workload != nullptr && !workload->Start()) {
     return false;
   }

simpleperf/event_attr.cpp

@@ -82,7 +82,7 @@ perf_event_attr CreateDefaultPerfEventAttr(const EventType& event_type) {
   attr.config = event_type.config;
   attr.mmap = 1;
   attr.comm = 1;
-  attr.disabled = 1;
+  attr.disabled = 0;
   // Changing read_format affects the layout of the data read from perf_event_file, namely
   // PerfCounter in event_fd.h.
   attr.read_format =

simpleperf/event_fd.cpp

@@ -95,24 +95,6 @@ uint64_t EventFd::Id() const {
   return id_;
 }
 
-bool EventFd::EnableEvent() {
-  int result = ioctl(perf_event_fd_, PERF_EVENT_IOC_ENABLE, 0);
-  if (result < 0) {
-    PLOG(ERROR) << "ioctl(enable) " << Name() << " failed";
-    return false;
-  }
-  return true;
-}
-
-bool EventFd::DisableEvent() {
-  int result = ioctl(perf_event_fd_, PERF_EVENT_IOC_DISABLE, 0);
-  if (result < 0) {
-    PLOG(ERROR) << "ioctl(disable) " << Name() << " failed";
-    return false;
-  }
-  return true;
-}
-
 bool EventFd::ReadCounter(PerfCounter* counter) const {
   CHECK(counter != nullptr);
   if (!android::base::ReadFully(perf_event_fd_, counter, sizeof(*counter))) {

simpleperf/event_fd.h

@@ -53,12 +53,6 @@ class EventFd {
     return cpu_;
   }
 
-  // It tells the kernel to start counting and recording events specified by this file.
-  bool EnableEvent();
-
-  // It tells the kernel to stop counting and recording events specified by this file.
-  bool DisableEvent();
-
   bool ReadCounter(PerfCounter* counter) const;
 
   // Call mmap() for this perf_event_file, so we can read sampled records from mapped area.

simpleperf/event_selection_set.cpp

@@ -81,7 +81,17 @@ void EventSelectionSet::UnionSampleType() {
 
 void EventSelectionSet::SetEnableOnExec(bool enable) {
   for (auto& selection : selections_) {
-    selection.event_attr.enable_on_exec = (enable ? 1 : 0);
+    // If sampling is enabled on exec, then it is disabled at startup, otherwise
+    // it should be enabled at startup. Don't use ioctl(PERF_EVENT_IOC_ENABLE)
+    // to enable it after perf_event_open(). Because some android kernels can't
+    // handle ioctl() well when cpu-hotplug happens. See http://b/25193162.
+    if (enable) {
+      selection.event_attr.enable_on_exec = 1;
+      selection.event_attr.disabled = 1;
+    } else {
+      selection.event_attr.enable_on_exec = 0;
+      selection.event_attr.disabled = 0;
+    }
   }
 }
 
@@ -218,17 +228,6 @@ bool EventSelectionSet::OpenEventFiles(const std::vector<pid_t>& threads,
   return true;
 }
 
-bool EventSelectionSet::EnableEvents() {
-  for (auto& selection : selections_) {
-    for (auto& event_fd : selection.event_fds) {
-      if (!event_fd->EnableEvent()) {
-        return false;
-      }
-    }
-  }
-  return true;
-}
-
 bool EventSelectionSet::ReadCounters(std::vector<CountersInfo>* counters) {
   counters->clear();
   for (auto& selection : selections_) {

simpleperf/event_selection_set.h

@@ -70,7 +70,6 @@ class EventSelectionSet {
 
   bool OpenEventFilesForCpus(const std::vector<int>& cpus);
   bool OpenEventFilesForThreadsOnCpus(const std::vector<pid_t>& threads, std::vector<int> cpus);
-  bool EnableEvents();
   bool ReadCounters(std::vector<CountersInfo>* counters);
   void PreparePollForEventFiles(std::vector<pollfd>* pollfds);
   bool MmapEventFiles(size_t mmap_pages);