Kernel: Track performance events for context switches

Cnidarias · May 19, 2021 · 8b2ace0 · 8b2ace0
1 parent c944408
commit 8b2ace0
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Showing 6 changed files with 29 additions and 2 deletions.
diff --git a/Kernel/PerformanceEventBuffer.cpp b/Kernel/PerformanceEventBuffer.cpp
@@ -107,6 +107,10 @@ KResult PerformanceEventBuffer::append_with_eip_and_ebp(ProcessID pid, ThreadID
  break;
  case PERF_EVENT_THREAD_EXIT:
  break;
+ case PERF_EVENT_CONTEXT_SWITCH:
+ event.data.context_switch.next_pid = arg1;
+ event.data.context_switch.next_tid = arg2;
+ break;
  default:
  return EINVAL;
  }
@@ -180,6 +184,11 @@ bool PerformanceEventBuffer::to_json_impl(Serializer& object) const
  case PERF_EVENT_THREAD_EXIT:
  event_object.add("type", "thread_exit");
  break;
+ case PERF_EVENT_CONTEXT_SWITCH:
+ event_object.add("type", "context_switch");
+ event_object.add("next_pid", static_cast<u64>(event.data.context_switch.next_pid));
+ event_object.add("next_tid", static_cast<u64>(event.data.context_switch.next_tid));
+ break;
  }
  event_object.add("pid", event.pid);
  event_object.add("tid", event.tid);

diff --git a/Kernel/PerformanceEventBuffer.h b/Kernel/PerformanceEventBuffer.h
@@ -47,6 +47,11 @@ struct [[gnu::packed]] ThreadCreatePerformanceEvent {
  pid_t parent_tid;
 };
 
+struct [[gnu::packed]] ContextSwitchPerformanceEvent {
+ pid_t next_pid;
+ u32 next_tid;
+};
+
 struct [[gnu::packed]] PerformanceEvent {
  u8 type { 0 };
  u8 stack_size { 0 };
@@ -62,6 +67,7 @@ struct [[gnu::packed]] PerformanceEvent {
  ProcessCreatePerformanceEvent process_create;
  ProcessExecPerformanceEvent process_exec;
  ThreadCreatePerformanceEvent thread_create;
+ ContextSwitchPerformanceEvent context_switch;
  } data;
  static constexpr size_t max_stack_frame_count = 64;
  FlatPtr stack[max_stack_frame_count];

diff --git a/Kernel/PerformanceManager.h b/Kernel/PerformanceManager.h
@@ -85,6 +85,13 @@ class PerformanceManager {
  }
  }
 
+ inline static void add_context_switch_perf_event(Thread& current_thread, Thread& next_thread)
+ {
+ if (auto* event_buffer = current_thread.process().current_perf_events_buffer()) {
+ [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_CONTEXT_SWITCH, next_thread.pid().value(), next_thread.tid().value(), nullptr);
+ }
+ }
+
  inline static void timer_tick(RegisterState const& regs)
  {
  static Time last_wakeup;

diff --git a/Kernel/Scheduler.cpp b/Kernel/Scheduler.cpp
@@ -10,6 +10,7 @@
 #include <AK/Time.h>
 #include <Kernel/Debug.h>
 #include <Kernel/Panic.h>
+#include <Kernel/PerformanceManager.h>
 #include <Kernel/Process.h>
 #include <Kernel/RTC.h>
 #include <Kernel/Scheduler.h>
@@ -365,6 +366,8 @@ bool Scheduler::context_switch(Thread* thread)
  }
  thread->set_state(Thread::Running);
 
+ PerformanceManager::add_context_switch_perf_event(*from_thread, *thread);
+
  proc.switch_context(from_thread, thread);
 
  // NOTE: from_thread at this point reflects the thread we were

diff --git a/Kernel/UnixTypes.h b/Kernel/UnixTypes.h
@@ -56,7 +56,8 @@ enum {
  PERF_EVENT_PROCESS_EXEC,
  PERF_EVENT_PROCESS_EXIT,
  PERF_EVENT_THREAD_CREATE,
- PERF_EVENT_THREAD_EXIT
+ PERF_EVENT_THREAD_EXIT,
+ PERF_EVENT_CONTEXT_SWITCH,
 };
 
 #define WNOHANG 1

diff --git a/Userland/Libraries/LibC/serenity.h b/Userland/Libraries/LibC/serenity.h
@@ -85,7 +85,8 @@ enum {
  PERF_EVENT_PROCESS_EXEC,
  PERF_EVENT_PROCESS_EXIT,
  PERF_EVENT_THREAD_CREATE,
- PERF_EVENT_THREAD_EXIT
+ PERF_EVENT_THREAD_EXIT,
+ PERF_EVENT_CONTEXT_SWITCH,
 };
 
 int perf_event(int type, uintptr_t arg1, uintptr_t arg2);