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Kernel+Profiler: Track lost time between profiler timer ticks

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We can lose profiling timer events for a few reasons, for example
disabled interrupts or system slowness. This accounts for lost
time between CPU samples by adding a field lost_samples to each
profiling event which tracks how many samples were lost immediately
preceding the event.
This commit is contained in:
Gunnar Beutner 2021-05-13 22:14:07 +02:00 • committed by Andreas Kling
parent 8614d18956
commit c41f13f10b
8 changed files with 30 additions and 11 deletions
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12
Kernel/PerformanceEventBuffer.cpp
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@ -25,7 +25,7 @@ NEVER_INLINE KResult PerformanceEventBuffer::append(int type, FlatPtr arg1, Flat
FlatPtr ebp;
asm volatile("movl %%ebp, %%eax"
: "=a"(ebp));
return append_with_eip_and_ebp(current_thread->pid(), current_thread->tid(), 0, ebp, type, arg1, arg2, arg3);
return append_with_eip_and_ebp(current_thread->pid(), current_thread->tid(), 0, ebp, type, 0, arg1, arg2, arg3);
}
static Vector<FlatPtr, PerformanceEvent::max_stack_frame_count> raw_backtrace(FlatPtr ebp, FlatPtr eip)
@ -55,13 +55,14 @@ static Vector<FlatPtr, PerformanceEvent::max_stack_frame_count> raw_backtrace(Fl
}
KResult PerformanceEventBuffer::append_with_eip_and_ebp(ProcessID pid, ThreadID tid,
u32 eip, u32 ebp, int type, FlatPtr arg1, FlatPtr arg2, const StringView& arg3)
u32 eip, u32 ebp, int type, u32 lost_samples, FlatPtr arg1, FlatPtr arg2, const StringView& arg3)
{
if (count() >= capacity())
return ENOBUFS;
PerformanceEvent event;
event.type = type;
event.lost_samples = lost_samples;
switch (type) {
case PERF_EVENT_SAMPLE:
@ -182,6 +183,7 @@ bool PerformanceEventBuffer::to_json_impl(Serializer& object) const
event_object.add("pid", event.pid);
event_object.add("tid", event.tid);
event_object.add("timestamp", event.timestamp);
event_object.add("lost_samples", i != 0 ? event.lost_samples : 0);
auto stack_array = event_object.add_array("stack");
for (size_t j = 0; j < event.stack_size; ++j) {
stack_array.add(event.stack[j]);
@ -220,17 +222,17 @@ void PerformanceEventBuffer::add_process(const Process& process, ProcessEventTyp
[[maybe_unused]] auto rc = append_with_eip_and_ebp(process.pid(), 0, 0, 0,
event_type == ProcessEventType::Create ? PERF_EVENT_PROCESS_CREATE : PERF_EVENT_PROCESS_EXEC,
process.pid().value(), 0, executable);
0, process.pid().value(), 0, executable);
process.for_each_thread([&](auto& thread) {
[[maybe_unused]] auto rc = append_with_eip_and_ebp(process.pid(), thread.tid().value(),
0, 0, PERF_EVENT_THREAD_CREATE, 0, 0, nullptr);
0, 0, PERF_EVENT_THREAD_CREATE, 0, 0, 0, nullptr);
return IterationDecision::Continue;
});
for (auto& region : process.space().regions()) {
[[maybe_unused]] auto rc = append_with_eip_and_ebp(process.pid(), 0,
0, 0, PERF_EVENT_MMAP, region->range().base().get(), region->range().size(), region->name());
0, 0, PERF_EVENT_MMAP, 0, region->range().base().get(), region->range().size(), region->name());
}
}