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LeafOS / LeafOS-Project / android_art / fb223f91cda4515eb6ceb32c19f02a1b0e25426a / . / runtime / trace.cc
blob: 29f67f075e70e9c698c2193605e2054a741ad5b8 [file] [log] [blame]
/*
* Copyright (C) 2011 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 "trace.h"
#include <sys/uio.h>
#include <unistd.h>
#include "android-base/macros.h"
#include "android-base/stringprintf.h"
#include "art_method-inl.h"
#include "base/casts.h"
#include "base/enums.h"
#include "base/os.h"
#include "base/stl_util.h"
#include "base/systrace.h"
#include "base/time_utils.h"
#include "base/unix_file/fd_file.h"
#include "base/utils.h"
#include "class_linker.h"
#include "common_throws.h"
#include "debugger.h"
#include "dex/descriptors_names.h"
#include "dex/dex_file-inl.h"
#include "entrypoints/quick/quick_entrypoints.h"
#include "gc/scoped_gc_critical_section.h"
#include "instrumentation.h"
#include "jit/jit.h"
#include "jit/jit_code_cache.h"
#include "mirror/class-inl.h"
#include "mirror/dex_cache-inl.h"
#include "mirror/object-inl.h"
#include "mirror/object_array-inl.h"
#include "nativehelper/scoped_local_ref.h"
#include "scoped_thread_state_change-inl.h"
#include "stack.h"
#include "thread.h"
#include "thread_list.h"
namespace art HIDDEN {
using android::base::StringPrintf;
static constexpr size_t TraceActionBits = MinimumBitsToStore(
static_cast<size_t>(kTraceMethodActionMask));
static constexpr uint8_t kOpNewMethod = 1U;
static constexpr uint8_t kOpNewThread = 2U;
static constexpr uint8_t kOpTraceSummary = 3U;
static const char kTraceTokenChar = '*';
static const uint16_t kTraceHeaderLength = 32;
static const uint32_t kTraceMagicValue = 0x574f4c53;
static const uint16_t kTraceVersionSingleClock = 2;
static const uint16_t kTraceVersionDualClock = 3;
static const uint16_t kTraceRecordSizeSingleClock = 10; // using v2
static const uint16_t kTraceRecordSizeDualClock = 14; // using v3 with two timestamps
static const size_t kNumTracePoolBuffers = 32;
TraceClockSource Trace::default_clock_source_ = kDefaultTraceClockSource;
Trace* volatile Trace::the_trace_ = nullptr;
pthread_t Trace::sampling_pthread_ = 0U;
std::unique_ptr<std::vector<ArtMethod*>> Trace::temp_stack_trace_;
// The key identifying the tracer to update instrumentation.
static constexpr const char* kTracerInstrumentationKey = "Tracer";
static TraceAction DecodeTraceAction(uint32_t tmid) {
return static_cast<TraceAction>(tmid & kTraceMethodActionMask);
}
namespace {
// Scaling factor to convert timestamp counter into wall clock time reported in micro seconds.
// This is initialized at the start of tracing using the timestamp counter update frequency.
// See InitializeTimestampCounters for more details.
double tsc_to_microsec_scaling_factor = -1.0;
uint64_t GetTimestamp() {
uint64_t t = 0;
#if defined(__arm__)
// On ARM 32 bit, we don't always have access to the timestamp counters from user space. There is
// no easy way to check if it is safe to read the timestamp counters. There is HWCAP_EVTSTRM which
// is set when generic timer is available but not necessarily from the user space. Kernel disables
// access to generic timer when there are known problems on the target CPUs. Sometimes access is
// disabled only for 32-bit processes even when 64-bit processes can accesses the timer from user
// space. These are not reflected in the HWCAP_EVTSTRM capability.So just fallback to
// clock_gettime on these processes. See b/289178149 for more discussion.
t = MicroTime();
#elif defined(__aarch64__)
// See Arm Architecture Registers Armv8 section System Registers
asm volatile("mrs %0, cntvct_el0" : "=r"(t));
#elif defined(__i386__) || defined(__x86_64__)
// rdtsc returns two 32-bit values in rax and rdx even on 64-bit architectures.
unsigned int lo, hi;
asm volatile("rdtsc" : "=a"(lo), "=d"(hi));
t = (static_cast<uint64_t>(hi) << 32) | lo;
#elif defined(__riscv)
asm volatile("rdtime %0" : "=r"(t));
#else
t = MicroTime();
#endif
return t;
}
#if defined(__i386__) || defined(__x86_64__) || defined(__aarch64__)
// Here we compute the scaling factor by sleeping for a millisecond. Alternatively, we could
// generate raw timestamp counter and also time using clock_gettime at the start and the end of the
// trace. We can compute the frequency of timestamp counter upadtes in the post processing step
// using these two samples. However, that would require a change in Android Studio which is the main
// consumer of these profiles. For now, just compute the frequency of tsc updates here.
double computeScalingFactor() {
uint64_t start = MicroTime();
uint64_t start_tsc = GetTimestamp();
// Sleep for one millisecond.
usleep(1000);
uint64_t diff_tsc = GetTimestamp() - start_tsc;
uint64_t diff_time = MicroTime() - start;
double scaling_factor = static_cast<double>(diff_time) / diff_tsc;
DCHECK(scaling_factor > 0.0) << scaling_factor;
return scaling_factor;
}
#endif
#if defined(__i386__) || defined(__x86_64__)
double GetScalingFactorForX86() {
uint32_t eax, ebx, ecx;
asm volatile("cpuid" : "=a"(eax), "=b"(ebx), "=c"(ecx) : "a"(0x0), "c"(0));
if (eax < 0x15) {
// There is no 15H - Timestamp counter and core crystal clock information
// leaf. Just compute the frequency.
return computeScalingFactor();
}
// From Intel architecture-instruction-set-extensions-programming-reference:
// EBX[31:0]/EAX[31:0] indicates the ratio of the TSC frequency and the
// core crystal clock frequency.
// If EBX[31:0] is 0, the TSC and "core crystal clock" ratio is not enumerated.
// If ECX is 0, the nominal core crystal clock frequency is not enumerated.
// "TSC frequency" = "core crystal clock frequency" * EBX/EAX.
// The core crystal clock may differ from the reference clock, bus clock, or core clock
// frequencies.
// EAX Bits 31 - 00: An unsigned integer which is the denominator of the
// TSC/"core crystal clock" ratio.
// EBX Bits 31 - 00: An unsigned integer which is the numerator of the
// TSC/"core crystal clock" ratio.
// ECX Bits 31 - 00: An unsigned integer which is the nominal frequency of the core
// crystal clock in Hz.
// EDX Bits 31 - 00: Reserved = 0.
asm volatile("cpuid" : "=a"(eax), "=b"(ebx), "=c"(ecx) : "a"(0x15), "c"(0));
if (ebx == 0 || ecx == 0) {
return computeScalingFactor();
}
double coreCrystalFreq = ecx;
// frequency = coreCrystalFreq * (ebx / eax)
// scaling_factor = seconds_to_microseconds / frequency
// = seconds_to_microseconds * eax / (coreCrystalFreq * ebx)
double seconds_to_microseconds = 1000 * 1000;
double scaling_factor = (seconds_to_microseconds * eax) / (coreCrystalFreq * ebx);
return scaling_factor;
}
#endif
void InitializeTimestampCounters() {
// It is sufficient to initialize this once for the entire execution. Just return if it is
// already initialized.
if (tsc_to_microsec_scaling_factor > 0.0) {
return;
}
#if defined(__arm__)
// On ARM 32 bit, we don't always have access to the timestamp counters from
// user space. Seem comment in GetTimestamp for more details.
tsc_to_microsec_scaling_factor = 1.0;
#elif defined(__aarch64__)
double seconds_to_microseconds = 1000 * 1000;
uint64_t freq = 0;
// See Arm Architecture Registers Armv8 section System Registers
asm volatile("mrs %0, cntfrq_el0" : "=r"(freq));
if (freq == 0) {
// It is expected that cntfrq_el0 is correctly setup during system initialization but some
// devices don't do this. In such cases fall back to computing the frequency. See b/315139000.
tsc_to_microsec_scaling_factor = computeScalingFactor();
} else {
tsc_to_microsec_scaling_factor = seconds_to_microseconds / static_cast<double>(freq);
}
#elif defined(__i386__) || defined(__x86_64__)
tsc_to_microsec_scaling_factor = GetScalingFactorForX86();
#else
tsc_to_microsec_scaling_factor = 1.0;
#endif
}
ALWAYS_INLINE uint64_t GetMicroTime(uint64_t counter) {
DCHECK(tsc_to_microsec_scaling_factor > 0.0) << tsc_to_microsec_scaling_factor;
return tsc_to_microsec_scaling_factor * counter;
}
} // namespace
bool TraceWriter::HasMethodEncoding(ArtMethod* method) {
return art_method_id_map_.find(method) != art_method_id_map_.end();
}
std::pair<uint32_t, bool> TraceWriter::GetMethodEncoding(ArtMethod* method) {
auto it = art_method_id_map_.find(method);
if (it != art_method_id_map_.end()) {
return std::pair<uint32_t, bool>(it->second, false);
} else {
uint32_t idx = current_method_index_;
art_method_id_map_.emplace(method, idx);
current_method_index_++;
return std::pair<uint32_t, bool>(idx, true);
}
}
uint16_t TraceWriter::GetThreadEncoding(pid_t thread_id) {
auto it = thread_id_map_.find(thread_id);
if (it != thread_id_map_.end()) {
return it->second;
}
uint16_t idx = current_thread_index_;
thread_id_map_.emplace(thread_id, current_thread_index_);
DCHECK_LT(current_thread_index_, (1 << 16) - 2);
current_thread_index_++;
return idx;
}
class TraceWriterTask final : public SelfDeletingTask {
public:
TraceWriterTask(
TraceWriter* trace_writer, int index, uintptr_t* buffer, size_t cur_offset, size_t thread_id)
: trace_writer_(trace_writer),
index_(index),
buffer_(buffer),
cur_offset_(cur_offset),
thread_id_(thread_id),
reserve_buf_for_tid_(0) {}
void Run(Thread* self ATTRIBUTE_UNUSED) override {
std::unordered_map<ArtMethod*, std::string> method_infos;
{
ScopedObjectAccess soa(Thread::Current());
trace_writer_->PreProcessTraceForMethodInfos(buffer_, cur_offset_, method_infos);
}
trace_writer_->FlushBuffer(buffer_, cur_offset_, thread_id_, method_infos);
if (index_ == -1) {
// This was a temporary buffer we allocated since there are no more free buffers and we
// couldn't find one by flushing the pending tasks either. This should only happen when we
// have fewer buffers than the number of threads.
if (reserve_buf_for_tid_ == 0) {
// Just free the buffer here if it wasn't reserved for any thread.
delete[] buffer_;
}
} else {
trace_writer_->FetchTraceBufferForThread(index_, reserve_buf_for_tid_);
}
}
// Reserves the buffer for a particular thread. The thread is free to use this buffer once the
// task has finished running. This is used when there are no free buffers for the thread to use.
uintptr_t* ReserveBufferForTid(size_t tid) {
reserve_buf_for_tid_ = tid;
return buffer_;
}
private:
TraceWriter* trace_writer_;
int index_;
uintptr_t* buffer_;
size_t cur_offset_;
size_t thread_id_;
// Sometimes we want to acquire a buffer for a particular thread. This holds
// the tid of the thread that we want to acquire the buffer for. If this value
// is 0 then it means we can use it for other threads.
size_t reserve_buf_for_tid_;
};
std::vector<ArtMethod*>* Trace::AllocStackTrace() {
return (temp_stack_trace_.get() != nullptr) ? temp_stack_trace_.release() :
new std::vector<ArtMethod*>();
}
void Trace::FreeStackTrace(std::vector<ArtMethod*>* stack_trace) {
stack_trace->clear();
temp_stack_trace_.reset(stack_trace);
}
void Trace::SetDefaultClockSource(TraceClockSource clock_source) {
#if defined(__linux__)
default_clock_source_ = clock_source;
#else
if (clock_source != TraceClockSource::kWall) {
LOG(WARNING) << "Ignoring tracing request to use CPU time.";
}
#endif
}
static uint16_t GetTraceVersion(TraceClockSource clock_source) {
return (clock_source == TraceClockSource::kDual) ? kTraceVersionDualClock
: kTraceVersionSingleClock;
}
static uint16_t GetRecordSize(TraceClockSource clock_source) {
return (clock_source == TraceClockSource::kDual) ? kTraceRecordSizeDualClock
: kTraceRecordSizeSingleClock;
}
static uint16_t GetNumEntries(TraceClockSource clock_source) {
return (clock_source == TraceClockSource::kDual) ? kNumEntriesForDualClock
: kNumEntriesForWallClock;
}
bool UseThreadCpuClock(TraceClockSource clock_source) {
return (clock_source == TraceClockSource::kThreadCpu) ||
(clock_source == TraceClockSource::kDual);
}
bool UseWallClock(TraceClockSource clock_source) {
return (clock_source == TraceClockSource::kWall) || (clock_source == TraceClockSource::kDual);
}
void Trace::MeasureClockOverhead() {
if (UseThreadCpuClock(clock_source_)) {
Thread::Current()->GetCpuMicroTime();
}
if (UseWallClock(clock_source_)) {
GetTimestamp();
}
}
// Compute an average time taken to measure clocks.
uint32_t Trace::GetClockOverheadNanoSeconds() {
Thread* self = Thread::Current();
uint64_t start = self->GetCpuMicroTime();
for (int i = 4000; i > 0; i--) {
MeasureClockOverhead();
MeasureClockOverhead();
MeasureClockOverhead();
MeasureClockOverhead();
MeasureClockOverhead();
MeasureClockOverhead();
MeasureClockOverhead();
MeasureClockOverhead();
}
uint64_t elapsed_us = self->GetCpuMicroTime() - start;
return static_cast<uint32_t>(elapsed_us / 32);
}
// TODO: put this somewhere with the big-endian equivalent used by JDWP.
static void Append2LE(uint8_t* buf, uint16_t val) {
*buf++ = static_cast<uint8_t>(val);
*buf++ = static_cast<uint8_t>(val >> 8);
}
// TODO: put this somewhere with the big-endian equivalent used by JDWP.
static void Append4LE(uint8_t* buf, uint32_t val) {
*buf++ = static_cast<uint8_t>(val);
*buf++ = static_cast<uint8_t>(val >> 8);
*buf++ = static_cast<uint8_t>(val >> 16);
*buf++ = static_cast<uint8_t>(val >> 24);
}
// TODO: put this somewhere with the big-endian equivalent used by JDWP.
static void Append8LE(uint8_t* buf, uint64_t val) {
*buf++ = static_cast<uint8_t>(val);
*buf++ = static_cast<uint8_t>(val >> 8);
*buf++ = static_cast<uint8_t>(val >> 16);
*buf++ = static_cast<uint8_t>(val >> 24);
*buf++ = static_cast<uint8_t>(val >> 32);
*buf++ = static_cast<uint8_t>(val >> 40);
*buf++ = static_cast<uint8_t>(val >> 48);
*buf++ = static_cast<uint8_t>(val >> 56);
}
static void GetSample(Thread* thread, void* arg) REQUIRES_SHARED(Locks::mutator_lock_) {
std::vector<ArtMethod*>* const stack_trace = Trace::AllocStackTrace();
StackVisitor::WalkStack(
[&](const art::StackVisitor* stack_visitor) REQUIRES_SHARED(Locks::mutator_lock_) {
ArtMethod* m = stack_visitor->GetMethod();
// Ignore runtime frames (in particular callee save).
if (!m->IsRuntimeMethod()) {
stack_trace->push_back(m);
}
return true;
},
thread,
/* context= */ nullptr,
art::StackVisitor::StackWalkKind::kIncludeInlinedFrames);
Trace* the_trace = reinterpret_cast<Trace*>(arg);
the_trace->CompareAndUpdateStackTrace(thread, stack_trace);
}
static void ClearThreadStackTraceAndClockBase(Thread* thread, [[maybe_unused]] void* arg) {
thread->SetTraceClockBase(0);
std::vector<ArtMethod*>* stack_trace = thread->GetStackTraceSample();
thread->SetStackTraceSample(nullptr);
delete stack_trace;
}
void Trace::CompareAndUpdateStackTrace(Thread* thread,
std::vector<ArtMethod*>* stack_trace) {
CHECK_EQ(pthread_self(), sampling_pthread_);
std::vector<ArtMethod*>* old_stack_trace = thread->GetStackTraceSample();
// Update the thread's stack trace sample.
thread->SetStackTraceSample(stack_trace);
// Read timer clocks to use for all events in this trace.
uint32_t thread_clock_diff = 0;
uint64_t timestamp_counter = 0;
ReadClocks(thread, &thread_clock_diff, &timestamp_counter);
if (old_stack_trace == nullptr) {
// If there's no previous stack trace sample for this thread, log an entry event for all
// methods in the trace.
for (auto rit = stack_trace->rbegin(); rit != stack_trace->rend(); ++rit) {
LogMethodTraceEvent(thread, *rit, kTraceMethodEnter, thread_clock_diff, timestamp_counter);
}
} else {
// If there's a previous stack trace for this thread, diff the traces and emit entry and exit
// events accordingly.
auto old_rit = old_stack_trace->rbegin();
auto rit = stack_trace->rbegin();
// Iterate bottom-up over both traces until there's a difference between them.
while (old_rit != old_stack_trace->rend() && rit != stack_trace->rend() && *old_rit == *rit) {
old_rit++;
rit++;
}
// Iterate top-down over the old trace until the point where they differ, emitting exit events.
for (auto old_it = old_stack_trace->begin(); old_it != old_rit.base(); ++old_it) {
LogMethodTraceEvent(thread, *old_it, kTraceMethodExit, thread_clock_diff, timestamp_counter);
}
// Iterate bottom-up over the new trace from the point where they differ, emitting entry events.
for (; rit != stack_trace->rend(); ++rit) {
LogMethodTraceEvent(thread, *rit, kTraceMethodEnter, thread_clock_diff, timestamp_counter);
}
FreeStackTrace(old_stack_trace);
}
}
void* Trace::RunSamplingThread(void* arg) {
Runtime* runtime = Runtime::Current();
intptr_t interval_us = reinterpret_cast<intptr_t>(arg);
CHECK_GE(interval_us, 0);
CHECK(runtime->AttachCurrentThread("Sampling Profiler", true, runtime->GetSystemThreadGroup(),
!runtime->IsAotCompiler()));
while (true) {
usleep(interval_us);
ScopedTrace trace("Profile sampling");
Thread* self = Thread::Current();
Trace* the_trace;
{
MutexLock mu(self, *Locks::trace_lock_);
the_trace = the_trace_;
if (the_trace_->stop_tracing_) {
break;
}
}
{
// Avoid a deadlock between a thread doing garbage collection
// and the profile sampling thread, by blocking GC when sampling
// thread stacks (see b/73624630).
gc::ScopedGCCriticalSection gcs(self,
art::gc::kGcCauseInstrumentation,
art::gc::kCollectorTypeInstrumentation);
ScopedSuspendAll ssa(__FUNCTION__);
MutexLock mu(self, *Locks::thread_list_lock_);
runtime->GetThreadList()->ForEach(GetSample, the_trace);
}
}
runtime->DetachCurrentThread();
return nullptr;
}
void Trace::Start(const char* trace_filename,
size_t buffer_size,
int flags,
TraceOutputMode output_mode,
TraceMode trace_mode,
int interval_us) {
std::unique_ptr<File> file(OS::CreateEmptyFileWriteOnly(trace_filename));
if (file == nullptr) {
std::string msg = android::base::StringPrintf("Unable to open trace file '%s'", trace_filename);
PLOG(ERROR) << msg;
ScopedObjectAccess soa(Thread::Current());
Thread::Current()->ThrowNewException("Ljava/lang/RuntimeException;", msg.c_str());
return;
}
Start(std::move(file), buffer_size, flags, output_mode, trace_mode, interval_us);
}
void Trace::Start(int trace_fd,
size_t buffer_size,
int flags,
TraceOutputMode output_mode,
TraceMode trace_mode,
int interval_us) {
if (trace_fd < 0) {
std::string msg = android::base::StringPrintf("Unable to start tracing with invalid fd %d",
trace_fd);
LOG(ERROR) << msg;
ScopedObjectAccess soa(Thread::Current());
Thread::Current()->ThrowNewException("Ljava/lang/RuntimeException;", msg.c_str());
return;
}
std::unique_ptr<File> file(new File(trace_fd, /* path= */ "tracefile", /* check_usage= */ true));
Start(std::move(file), buffer_size, flags, output_mode, trace_mode, interval_us);
}
void Trace::StartDDMS(size_t buffer_size,
int flags,
TraceMode trace_mode,
int interval_us) {
Start(std::unique_ptr<File>(),
buffer_size,
flags,
TraceOutputMode::kDDMS,
trace_mode,
interval_us);
}
void Trace::Start(std::unique_ptr<File>&& trace_file_in,
size_t buffer_size,
int flags,
TraceOutputMode output_mode,
TraceMode trace_mode,
int interval_us) {
// We own trace_file now and are responsible for closing it. To account for error situations, use
// a specialized unique_ptr to ensure we close it on the way out (if it hasn't been passed to a
// Trace instance).
auto deleter = [](File* file) {
if (file != nullptr) {
file->MarkUnchecked(); // Don't deal with flushing requirements.
[[maybe_unused]] int result = file->Close();
delete file;
}
};
std::unique_ptr<File, decltype(deleter)> trace_file(trace_file_in.release(), deleter);
Thread* self = Thread::Current();
{
MutexLock mu(self, *Locks::trace_lock_);
if (the_trace_ != nullptr) {
LOG(ERROR) << "Trace already in progress, ignoring this request";
return;
}
}
// Check interval if sampling is enabled
if (trace_mode == TraceMode::kSampling && interval_us <= 0) {
LOG(ERROR) << "Invalid sampling interval: " << interval_us;
ScopedObjectAccess soa(self);
ThrowRuntimeException("Invalid sampling interval: %d", interval_us);
return;
}
// Initialize the frequency of timestamp counter updates here. This is needed
// to get wallclock time from timestamp counter values.
InitializeTimestampCounters();
Runtime* runtime = Runtime::Current();
// Enable count of allocs if specified in the flags.
bool enable_stats = false;
// Create Trace object.
{
// Suspend JIT here since we are switching runtime to debuggable. Debuggable runtimes cannot use
// JITed code from before so we need to invalidated all JITed code here. Enter suspend JIT scope
// to prevent any races with ongoing JIT compilations.
jit::ScopedJitSuspend suspend_jit;
// Required since EnableMethodTracing calls ConfigureStubs which visits class linker classes.
gc::ScopedGCCriticalSection gcs(self,
gc::kGcCauseInstrumentation,
gc::kCollectorTypeInstrumentation);
ScopedSuspendAll ssa(__FUNCTION__);
MutexLock mu(self, *Locks::trace_lock_);
if (the_trace_ != nullptr) {
LOG(ERROR) << "Trace already in progress, ignoring this request";
} else {
enable_stats = (flags & kTraceCountAllocs) != 0;
the_trace_ = new Trace(trace_file.release(), buffer_size, flags, output_mode, trace_mode);
if (trace_mode == TraceMode::kSampling) {
CHECK_PTHREAD_CALL(pthread_create, (&sampling_pthread_, nullptr, &RunSamplingThread,
reinterpret_cast<void*>(interval_us)),
"Sampling profiler thread");
the_trace_->interval_us_ = interval_us;
} else {
if (!runtime->IsJavaDebuggable()) {
art::jit::Jit* jit = runtime->GetJit();
if (jit != nullptr) {
jit->GetCodeCache()->InvalidateAllCompiledCode();
jit->GetCodeCache()->TransitionToDebuggable();
jit->GetJitCompiler()->SetDebuggableCompilerOption(true);
}
runtime->SetRuntimeDebugState(art::Runtime::RuntimeDebugState::kJavaDebuggable);
runtime->GetInstrumentation()->UpdateEntrypointsForDebuggable();
runtime->DeoptimizeBootImage();
}
// For thread cpu clocks, we need to make a kernel call and hence we call into c++ to
// support them.
bool is_fast_trace = !UseThreadCpuClock(the_trace_->GetClockSource());
#if defined(__arm__)
// On ARM 32 bit, we don't always have access to the timestamp counters from
// user space. Seem comment in GetTimestamp for more details.
is_fast_trace = false;
#endif
runtime->GetInstrumentation()->AddListener(
the_trace_,
instrumentation::Instrumentation::kMethodEntered |
instrumentation::Instrumentation::kMethodExited |
instrumentation::Instrumentation::kMethodUnwind,
is_fast_trace);
runtime->GetInstrumentation()->EnableMethodTracing(kTracerInstrumentationKey,
the_trace_,
/*needs_interpreter=*/false);
}
}
}
// Can't call this when holding the mutator lock.
if (enable_stats) {
runtime->SetStatsEnabled(true);
}
}
void Trace::StopTracing(bool flush_entries) {
Runtime* const runtime = Runtime::Current();
Thread* const self = Thread::Current();
pthread_t sampling_pthread = 0U;
{
MutexLock mu(self, *Locks::trace_lock_);
if (the_trace_ == nullptr) {
LOG(ERROR) << "Trace stop requested, but no trace currently running";
return;
}
// Tell sampling_pthread_ to stop tracing.
the_trace_->stop_tracing_ = true;
sampling_pthread = sampling_pthread_;
}
// Make sure that we join before we delete the trace since we don't want to have
// the sampling thread access a stale pointer. This finishes since the sampling thread exits when
// the_trace_ is null.
if (sampling_pthread != 0U) {
CHECK_PTHREAD_CALL(pthread_join, (sampling_pthread, nullptr), "sampling thread shutdown");
}
// Make a copy of the_trace_, so it can be flushed later. We want to reset
// the_trace_ to nullptr in suspend all scope to prevent any races
Trace* the_trace = the_trace_;
bool stop_alloc_counting = (the_trace->flags_ & Trace::kTraceCountAllocs) != 0;
// Stop the trace sources adding more entries to the trace buffer and synchronise stores.
{
gc::ScopedGCCriticalSection gcs(
self, gc::kGcCauseInstrumentation, gc::kCollectorTypeInstrumentation);
jit::ScopedJitSuspend suspend_jit;
ScopedSuspendAll ssa(__FUNCTION__);
if (the_trace->trace_mode_ == TraceMode::kSampling) {
MutexLock mu(self, *Locks::thread_list_lock_);
runtime->GetThreadList()->ForEach(ClearThreadStackTraceAndClockBase, nullptr);
} else {
// For thread cpu clocks, we need to make a kernel call and hence we call into c++ to support
// them.
bool is_fast_trace = !UseThreadCpuClock(the_trace_->GetClockSource());
#if defined(__arm__)
// On ARM 32 bit, we don't always have access to the timestamp counters from
// user space. Seem comment in GetTimestamp for more details.
is_fast_trace = false;
#endif
runtime->GetInstrumentation()->RemoveListener(
the_trace,
instrumentation::Instrumentation::kMethodEntered |
instrumentation::Instrumentation::kMethodExited |
instrumentation::Instrumentation::kMethodUnwind,
is_fast_trace);
runtime->GetInstrumentation()->DisableMethodTracing(kTracerInstrumentationKey);
}
// Flush thread specific buffer from all threads before resetting the_trace_ to nullptr.
// We also flush the buffer when destroying a thread which expects the_trace_ to be valid so
// make sure that the per-thread buffer is reset before resetting the_trace_.
{
MutexLock tl_lock(Thread::Current(), *Locks::thread_list_lock_);
for (Thread* thread : Runtime::Current()->GetThreadList()->GetList()) {
if (thread->GetMethodTraceBuffer() != nullptr) {
// We may have pending requests to flush the data. So just enqueue a
// request to flush the current buffer so all the requests are
// processed in order.
the_trace->trace_writer_->FlushBuffer(
thread, /* is_sync= */ false, /* free_buffer= */ true);
}
}
}
// Reset the_trace_ by taking a trace_lock
MutexLock mu(self, *Locks::trace_lock_);
the_trace_ = nullptr;
sampling_pthread_ = 0U;
}
// At this point, code may read buf_ as its writers are shutdown
// and the ScopedSuspendAll above has ensured all stores to buf_
// are now visible.
the_trace->trace_writer_->FinishTracing(the_trace->flags_, flush_entries);
delete the_trace;
if (stop_alloc_counting) {
// Can be racy since SetStatsEnabled is not guarded by any locks.
runtime->SetStatsEnabled(false);
}
}
void Trace::FlushThreadBuffer(Thread* self) {
MutexLock mu(self, *Locks::trace_lock_);
the_trace_->trace_writer_->FlushBuffer(self, /* is_sync= */ false, /* free_buffer= */ true);
}
void Trace::Abort() {
// Do not write anything anymore.
StopTracing(/* flush_entries= */ false);
}
void Trace::Stop() {
// Finish writing.
StopTracing(/* flush_entries= */ true);
}
void Trace::Shutdown() {
if (GetMethodTracingMode() != kTracingInactive) {
Stop();
}
}
TracingMode Trace::GetMethodTracingMode() {
MutexLock mu(Thread::Current(), *Locks::trace_lock_);
if (the_trace_ == nullptr) {
return kTracingInactive;
} else {
switch (the_trace_->trace_mode_) {
case TraceMode::kSampling:
return kSampleProfilingActive;
case TraceMode::kMethodTracing:
return kMethodTracingActive;
}
LOG(FATAL) << "Unreachable";
UNREACHABLE();
}
}
static constexpr size_t kMinBufSize = 18U; // Trace header is up to 18B.
// Size of per-thread buffer size. The value is chosen arbitrarily. This value
// should be greater than kMinBufSize.
static constexpr size_t kPerThreadBufSize = 512 * 1024;
static_assert(kPerThreadBufSize > kMinBufSize);
// On average we need 12 bytes for encoding an entry. We typically use two
// entries in per-thread buffer, the scaling factor is 6.
static constexpr size_t kScalingFactorEncodedEntries = 6;
namespace {
TraceClockSource GetClockSourceFromFlags(int flags) {
bool need_wall = flags & Trace::TraceFlag::kTraceClockSourceWallClock;
bool need_thread_cpu = flags & Trace::TraceFlag::kTraceClockSourceThreadCpu;
if (need_wall && need_thread_cpu) {
return TraceClockSource::kDual;
} else if (need_wall) {
return TraceClockSource::kWall;
} else if (need_thread_cpu) {
return TraceClockSource::kThreadCpu;
} else {
return kDefaultTraceClockSource;
}
}
} // namespace
TraceWriter::TraceWriter(File* trace_file,
TraceOutputMode output_mode,
TraceClockSource clock_source,
size_t buffer_size,
int num_trace_buffers,
uint32_t clock_overhead_ns)
: trace_file_(trace_file),
trace_output_mode_(output_mode),
clock_source_(clock_source),
buf_(new uint8_t[std::max(kMinBufSize, buffer_size)]()),
buffer_size_(std::max(kMinBufSize, buffer_size)),
start_time_(GetMicroTime(GetTimestamp())),
overflow_(false),
clock_overhead_ns_(clock_overhead_ns),
owner_tids_(num_trace_buffers),
tracing_lock_("tracing lock", LockLevel::kTracingStreamingLock) {
uint16_t trace_version = GetTraceVersion(clock_source_);
if (output_mode == TraceOutputMode::kStreaming) {
trace_version |= 0xF0U;
}
// Set up the beginning of the trace.
memset(buf_.get(), 0, kTraceHeaderLength);
Append4LE(buf_.get(), kTraceMagicValue);
Append2LE(buf_.get() + 4, trace_version);
Append2LE(buf_.get() + 6, kTraceHeaderLength);
Append8LE(buf_.get() + 8, start_time_);
if (trace_version >= kTraceVersionDualClock) {
uint16_t record_size = GetRecordSize(clock_source_);
Append2LE(buf_.get() + 16, record_size);
}
static_assert(18 <= kMinBufSize, "Minimum buffer size not large enough for trace header");
cur_offset_ = kTraceHeaderLength;
if (output_mode == TraceOutputMode::kStreaming) {
// Flush the header information to the file. We use a per thread buffer, so
// it is easier to just write the header information directly to file.
if (!trace_file_->WriteFully(buf_.get(), kTraceHeaderLength)) {
PLOG(WARNING) << "Failed streaming a tracing event.";
}
cur_offset_ = 0;
}
// Thread index of 0 is a special identifier used to distinguish between trace
// event entries and thread / method info entries.
current_thread_index_ = 1;
// Don't create threadpool for a zygote. This would cause slowdown when forking because we need
// to stop and start this thread pool. Method tracing on zygote isn't a frequent use case and
// it is okay to flush on the main thread in such cases.
if (!Runtime::Current()->IsZygote()) {
thread_pool_.reset(TraceWriterThreadPool::Create("Trace writer pool"));
thread_pool_->StartWorkers(Thread::Current());
}
// Initialize the pool of per-thread buffers.
InitializeTraceBuffers();
}
Trace::Trace(File* trace_file,
size_t buffer_size,
int flags,
TraceOutputMode output_mode,
TraceMode trace_mode)
: flags_(flags),
trace_mode_(trace_mode),
clock_source_(GetClockSourceFromFlags(flags)),
interval_us_(0),
stop_tracing_(false) {
CHECK_IMPLIES(trace_file == nullptr, output_mode == TraceOutputMode::kDDMS);
// In streaming mode, we only need a buffer big enough to store data per each
// thread buffer. In non-streaming mode this is specified by the user and we
// stop tracing when the buffer is full.
size_t buf_size = (output_mode == TraceOutputMode::kStreaming) ?
kPerThreadBufSize * kScalingFactorEncodedEntries :
buffer_size;
trace_writer_.reset(new TraceWriter(trace_file,
output_mode,
clock_source_,
buf_size,
kNumTracePoolBuffers,
GetClockOverheadNanoSeconds()));
}
void TraceWriter::FinishTracing(int flags, bool flush_entries) {
Thread* self = Thread::Current();
if (flush_entries) {
if (thread_pool_ != nullptr) {
// Wait for any workers to be created. If we are stopping tracing as a part of runtime
// shutdown, any unstarted workers can create problems if they try attaching while shutting
// down.
thread_pool_->WaitForWorkersToBeCreated();
// Wait for any outstanding writer tasks to finish.
thread_pool_->Wait(self, /* do_work= */ true, /* may_hold_locks= */ true);
DCHECK_EQ(thread_pool_->GetTaskCount(self), 0u);
thread_pool_->StopWorkers(self);
}
size_t final_offset = 0;
if (trace_output_mode_ != TraceOutputMode::kStreaming) {
MutexLock mu(Thread::Current(), tracing_lock_);
final_offset = cur_offset_;
}
// Compute elapsed time.
uint64_t elapsed = GetMicroTime(GetTimestamp()) - start_time_;
std::ostringstream os;
os << StringPrintf("%cversion\n", kTraceTokenChar);
os << StringPrintf("%d\n", GetTraceVersion(clock_source_));
os << StringPrintf("data-file-overflow=%s\n", overflow_ ? "true" : "false");
if (UseThreadCpuClock(clock_source_)) {
if (UseWallClock(clock_source_)) {
os << StringPrintf("clock=dual\n");
} else {
os << StringPrintf("clock=thread-cpu\n");
}
} else {
os << StringPrintf("clock=wall\n");
}
os << StringPrintf("elapsed-time-usec=%" PRIu64 "\n", elapsed);
if (trace_output_mode_ != TraceOutputMode::kStreaming) {
size_t num_records = (final_offset - kTraceHeaderLength) / GetRecordSize(clock_source_);
os << StringPrintf("num-method-calls=%zd\n", num_records);
}
os << StringPrintf("clock-call-overhead-nsec=%d\n", clock_overhead_ns_);
os << StringPrintf("vm=art\n");
os << StringPrintf("pid=%d\n", getpid());
if ((flags & Trace::kTraceCountAllocs) != 0) {
os << "alloc-count=" << Runtime::Current()->GetStat(KIND_ALLOCATED_OBJECTS) << "\n";
os << "alloc-size=" << Runtime::Current()->GetStat(KIND_ALLOCATED_BYTES) << "\n";
os << "gc-count=" << Runtime::Current()->GetStat(KIND_GC_INVOCATIONS) << "\n";
}
os << StringPrintf("%cthreads\n", kTraceTokenChar);
DumpThreadList(os);
os << StringPrintf("%cmethods\n", kTraceTokenChar);
DumpMethodList(os);
os << StringPrintf("%cend\n", kTraceTokenChar);
std::string header(os.str());
if (trace_output_mode_ == TraceOutputMode::kStreaming) {
DCHECK_NE(trace_file_.get(), nullptr);
// It is expected that this method is called when all other threads are suspended, so there
// cannot be any writes to trace_file_ after finish tracing.
// Write a special token to mark the end of trace records and the start of
// trace summary.
uint8_t buf[7];
Append2LE(buf, 0);
buf[2] = kOpTraceSummary;
Append4LE(buf + 3, static_cast<uint32_t>(header.length()));
// Write the trace summary. The summary is identical to the file header when
// the output mode is not streaming (except for methods).
if (!trace_file_->WriteFully(buf, sizeof(buf)) ||
!trace_file_->WriteFully(header.c_str(), header.length())) {
PLOG(WARNING) << "Failed streaming a tracing event.";
}
} else {
if (trace_file_.get() == nullptr) {
std::vector<uint8_t> data;
data.resize(header.length() + final_offset);
memcpy(data.data(), header.c_str(), header.length());
memcpy(data.data() + header.length(), buf_.get(), final_offset);
Runtime::Current()->GetRuntimeCallbacks()->DdmPublishChunk(CHUNK_TYPE("MPSE"),
ArrayRef<const uint8_t>(data));
} else {
if (!trace_file_->WriteFully(header.c_str(), header.length()) ||
!trace_file_->WriteFully(buf_.get(), final_offset)) {
std::string detail(StringPrintf("Trace data write failed: %s", strerror(errno)));
PLOG(ERROR) << detail;
ThrowRuntimeException("%s", detail.c_str());
}
}
}
} else {
// This is only called from the child process post fork to abort the trace.
// We shouldn't have any workers in the thread pool here.
DCHECK_EQ(thread_pool_, nullptr);
}
if (trace_file_.get() != nullptr) {
// Do not try to erase, so flush and close explicitly.
if (flush_entries) {
if (trace_file_->Flush() != 0) {
PLOG(WARNING) << "Could not flush trace file.";
}
} else {
trace_file_->MarkUnchecked(); // Do not trigger guard.
}
if (trace_file_->Close() != 0) {
PLOG(ERROR) << "Could not close trace file.";
}
}
}
void Trace::DexPcMoved([[maybe_unused]] Thread* thread,
[[maybe_unused]] Handle<mirror::Object> this_object,
ArtMethod* method,
uint32_t new_dex_pc) {
// We're not recorded to listen to this kind of event, so complain.
LOG(ERROR) << "Unexpected dex PC event in tracing " << ArtMethod::PrettyMethod(method)
<< " " << new_dex_pc;
}
void Trace::FieldRead([[maybe_unused]] Thread* thread,
[[maybe_unused]] Handle<mirror::Object> this_object,
ArtMethod* method,
uint32_t dex_pc,
[[maybe_unused]] ArtField* field) REQUIRES_SHARED(Locks::mutator_lock_) {
// We're not recorded to listen to this kind of event, so complain.
LOG(ERROR) << "Unexpected field read event in tracing " << ArtMethod::PrettyMethod(method)
<< " " << dex_pc;
}
void Trace::FieldWritten([[maybe_unused]] Thread* thread,
[[maybe_unused]] Handle<mirror::Object> this_object,
ArtMethod* method,
uint32_t dex_pc,
[[maybe_unused]] ArtField* field,
[[maybe_unused]] const JValue& field_value)
REQUIRES_SHARED(Locks::mutator_lock_) {
// We're not recorded to listen to this kind of event, so complain.
LOG(ERROR) << "Unexpected field write event in tracing " << ArtMethod::PrettyMethod(method)
<< " " << dex_pc;
}
void Trace::MethodEntered(Thread* thread, ArtMethod* method) {
uint32_t thread_clock_diff = 0;
uint64_t timestamp_counter = 0;
ReadClocks(thread, &thread_clock_diff, &timestamp_counter);
LogMethodTraceEvent(thread, method, kTraceMethodEnter, thread_clock_diff, timestamp_counter);
}
void Trace::MethodExited(Thread* thread,
ArtMethod* method,
[[maybe_unused]] instrumentation::OptionalFrame frame,
[[maybe_unused]] JValue& return_value) {
uint32_t thread_clock_diff = 0;
uint64_t timestamp_counter = 0;
ReadClocks(thread, &thread_clock_diff, &timestamp_counter);
LogMethodTraceEvent(thread, method, kTraceMethodExit, thread_clock_diff, timestamp_counter);
}
void Trace::MethodUnwind(Thread* thread, ArtMethod* method, [[maybe_unused]] uint32_t dex_pc) {
uint32_t thread_clock_diff = 0;
uint64_t timestamp_counter = 0;
ReadClocks(thread, &thread_clock_diff, &timestamp_counter);
LogMethodTraceEvent(thread, method, kTraceUnroll, thread_clock_diff, timestamp_counter);
}
void Trace::ExceptionThrown([[maybe_unused]] Thread* thread,
[[maybe_unused]] Handle<mirror::Throwable> exception_object)
REQUIRES_SHARED(Locks::mutator_lock_) {
LOG(ERROR) << "Unexpected exception thrown event in tracing";
}
void Trace::ExceptionHandled([[maybe_unused]] Thread* thread,
[[maybe_unused]] Handle<mirror::Throwable> exception_object)
REQUIRES_SHARED(Locks::mutator_lock_) {
LOG(ERROR) << "Unexpected exception thrown event in tracing";
}
void Trace::Branch(Thread* /*thread*/, ArtMethod* method,
uint32_t /*dex_pc*/, int32_t /*dex_pc_offset*/)
REQUIRES_SHARED(Locks::mutator_lock_) {
LOG(ERROR) << "Unexpected branch event in tracing" << ArtMethod::PrettyMethod(method);
}
void Trace::WatchedFramePop([[maybe_unused]] Thread* self,
[[maybe_unused]] const ShadowFrame& frame) {
LOG(ERROR) << "Unexpected WatchedFramePop event in tracing";
}
void Trace::ReadClocks(Thread* thread, uint32_t* thread_clock_diff, uint64_t* timestamp_counter) {
if (UseThreadCpuClock(clock_source_)) {
uint64_t clock_base = thread->GetTraceClockBase();
if (UNLIKELY(clock_base == 0)) {
// First event, record the base time in the map.
uint64_t time = thread->GetCpuMicroTime();
thread->SetTraceClockBase(time);
} else {
*thread_clock_diff = thread->GetCpuMicroTime() - clock_base;
}
}
if (UseWallClock(clock_source_)) {
*timestamp_counter = GetTimestamp();
}
}
uintptr_t* TraceWriterThreadPool::FinishTaskAndClaimBuffer(size_t tid) {
Thread* self = Thread::Current();
TraceWriterTask* task = static_cast<TraceWriterTask*>(TryGetTask(self));
if (task == nullptr) {
// TODO(mythria): We need to ensure we have at least as many buffers in the pool as the number
// of active threads for efficiency. It's a bit unlikely to hit this case and not trivial to
// handle this. So we haven't fixed this yet.
LOG(WARNING)
<< "Fewer buffers in the pool than the number of threads. Might cause some slowdown";
return nullptr;
}
uintptr_t* buffer = task->ReserveBufferForTid(tid);
task->Run(self);
task->Finalize();
return buffer;
}
std::string TraceWriter::GetMethodLine(const std::string& method_line, uint32_t method_index) {
return StringPrintf("%#x\t%s", (method_index << TraceActionBits), method_line.c_str());
}
std::string TraceWriter::GetMethodInfoLine(ArtMethod* method) {
method = method->GetInterfaceMethodIfProxy(kRuntimePointerSize);
return StringPrintf("%s\t%s\t%s\t%s\n",
PrettyDescriptor(method->GetDeclaringClassDescriptor()).c_str(),
method->GetName(),
method->GetSignature().ToString().c_str(),
method->GetDeclaringClassSourceFile());
}
void TraceWriter::RecordThreadInfo(Thread* thread) {
// This is the first event from this thread, so first record information about the thread.
std::string thread_name;
thread->GetThreadName(thread_name);
// In tests, we destroy VM after already detaching the current thread. We re-attach the current
// thread again as a "Shutdown thread" during the process of shutting down. So don't record
// information about shutdown threads since it overwrites the actual thread_name.
if (thread_name.compare("Shutdown thread") == 0) {
return;
}
MutexLock mu(Thread::Current(), tracing_lock_);
if (trace_output_mode_ != TraceOutputMode::kStreaming) {
threads_list_.Overwrite(GetThreadEncoding(thread->GetTid()), thread_name);
return;
}
static constexpr size_t kThreadNameHeaderSize = 7;
uint8_t header[kThreadNameHeaderSize];
Append2LE(header, 0);
header[2] = kOpNewThread;
Append2LE(header + 3, GetThreadEncoding(thread->GetTid()));
DCHECK(thread_name.length() < (1 << 16));
Append2LE(header + 5, static_cast<uint16_t>(thread_name.length()));
if (!trace_file_->WriteFully(header, kThreadNameHeaderSize) ||
!trace_file_->WriteFully(reinterpret_cast<const uint8_t*>(thread_name.c_str()),
thread_name.length())) {
PLOG(WARNING) << "Failed streaming a tracing event.";
}
}
void TraceWriter::PreProcessTraceForMethodInfos(
uintptr_t* method_trace_entries,
size_t current_offset,
std::unordered_map<ArtMethod*, std::string>& method_infos) {
// Compute the method infos before we process the entries. We don't want to assign an encoding
// for the method here. The expectation is that once we assign a method id we write it to the
// file before any other thread can see the method id. So we should assign method encoding while
// holding the tracing_lock_ and not release it till we flush the method info to the file. We
// don't want to flush entries to file while holding the mutator lock. We need the mutator lock to
// get method info. So we just precompute method infos without assigning a method encoding here.
// There may be a race and multiple threads computing the method info but only one of them would
// actually put into the method_id_map_.
MutexLock mu(Thread::Current(), tracing_lock_);
size_t num_entries = GetNumEntries(clock_source_);
DCHECK_EQ((kPerThreadBufSize - current_offset) % num_entries, 0u);
for (size_t entry_index = kPerThreadBufSize; entry_index != current_offset;) {
entry_index -= num_entries;
uintptr_t method_and_action = method_trace_entries[entry_index];
ArtMethod* method = reinterpret_cast<ArtMethod*>(method_and_action & kMaskTraceAction);
if (!HasMethodEncoding(method) && method_infos.find(method) == method_infos.end()) {
method_infos.emplace(method, std::move(GetMethodInfoLine(method)));
}
}
}
void TraceWriter::RecordMethodInfo(const std::string& method_info_line, uint32_t method_id) {
std::string method_line(GetMethodLine(method_info_line, method_id));
// Write a special block with the name.
static constexpr size_t kMethodNameHeaderSize = 5;
uint8_t method_header[kMethodNameHeaderSize];
DCHECK_LT(kMethodNameHeaderSize, kPerThreadBufSize);
Append2LE(method_header, 0);
method_header[2] = kOpNewMethod;
uint16_t method_line_length = static_cast<uint16_t>(method_line.length());
DCHECK(method_line.length() < (1 << 16));
Append2LE(method_header + 3, method_line_length);
const uint8_t* ptr = reinterpret_cast<const uint8_t*>(method_line.c_str());
if (!trace_file_->WriteFully(method_header, kMethodNameHeaderSize) ||
!trace_file_->WriteFully(ptr, method_line_length)) {
PLOG(WARNING) << "Failed streaming a tracing event.";
}
}
void TraceWriter::FlushAllThreadBuffers() {
ScopedThreadStateChange stsc(Thread::Current(), ThreadState::kSuspended);
ScopedSuspendAll ssa(__FUNCTION__);
MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
for (Thread* thread : Runtime::Current()->GetThreadList()->GetList()) {
if (thread->GetMethodTraceBuffer() != nullptr) {
FlushBuffer(thread, /* is_sync= */ true, /* free_buffer= */ false);
// We cannot flush anynore data, so just return.
if (overflow_) {
return;
}
}
}
return;
}
uintptr_t* TraceWriter::PrepareBufferForNewEntries(Thread* thread) {
if (trace_output_mode_ == TraceOutputMode::kStreaming) {
// In streaming mode, just flush the per-thread buffer and reuse the
// existing buffer for new entries.
FlushBuffer(thread, /* is_sync= */ false, /* free_buffer= */ false);
DCHECK_EQ(overflow_, false);
} else {
// For non-streaming mode, flush all the threads to check if we have space in the common
// buffer to record any future events.
FlushAllThreadBuffers();
}
if (overflow_) {
return nullptr;
}
return thread->GetMethodTraceBuffer();
}
void TraceWriter::InitializeTraceBuffers() {
for (size_t i = 0; i < owner_tids_.size(); i++) {
owner_tids_[i].store(0);
}
trace_buffer_.reset(new uintptr_t[kPerThreadBufSize * owner_tids_.size()]);
CHECK(trace_buffer_.get() != nullptr);
}
uintptr_t* TraceWriter::AcquireTraceBuffer(size_t tid) {
for (size_t index = 0; index < owner_tids_.size(); index++) {
size_t owner = 0;
if (owner_tids_[index].compare_exchange_strong(owner, tid)) {
return trace_buffer_.get() + index * kPerThreadBufSize;
}
}
// No free buffers, flush the buffer at the start of task queue synchronously and then use that
// buffer.
uintptr_t* buffer = thread_pool_->FinishTaskAndClaimBuffer(tid);
if (buffer == nullptr) {
// We couldn't find a free buffer even after flushing all the tasks. So allocate a new buffer
// here. This should only happen if we have more threads than the number of pool buffers.
// TODO(mythria): Add a check for the above case here.
buffer = new uintptr_t[kPerThreadBufSize];
CHECK(buffer != nullptr);
}
return buffer;
}
void TraceWriter::FetchTraceBufferForThread(int index, size_t tid) {
// Only the trace_writer_ thread can release the buffer.
owner_tids_[index].store(tid);
}
int TraceWriter::GetMethodTraceIndex(uintptr_t* current_buffer) {
if (current_buffer < trace_buffer_.get() ||
current_buffer > trace_buffer_.get() + (owner_tids_.size() - 1) * kPerThreadBufSize) {
// This was the temporary buffer we allocated.
return -1;
}
return (current_buffer - trace_buffer_.get()) / kPerThreadBufSize;
}
void TraceWriter::FlushBuffer(Thread* thread, bool is_sync, bool release) {
uintptr_t* method_trace_entries = thread->GetMethodTraceBuffer();
size_t* current_offset = thread->GetMethodTraceIndexPtr();
size_t tid = thread->GetTid();
DCHECK(method_trace_entries != nullptr);
if (is_sync || thread_pool_ == nullptr) {
std::unordered_map<ArtMethod*, std::string> method_infos;
PreProcessTraceForMethodInfos(method_trace_entries, *current_offset, method_infos);
FlushBuffer(method_trace_entries, *current_offset, tid, method_infos);
// This is a synchronous flush, so no need to allocate a new buffer. This is used either
// when the tracing has finished or in non-streaming mode.
// Just reset the buffer pointer to the initial value, so we can reuse the same buffer.
*current_offset = kPerThreadBufSize;
if (release) {
thread->SetMethodTraceBuffer(nullptr);
}
} else {
int old_index = GetMethodTraceIndex(method_trace_entries);
// The TraceWriterTask takes the ownership of the buffer and releases the buffer once the
// entries are flushed.
thread_pool_->AddTask(
Thread::Current(),
new TraceWriterTask(this, old_index, method_trace_entries, *current_offset, tid));
*current_offset = kPerThreadBufSize;
if (release) {
thread->SetMethodTraceBuffer(nullptr);
} else {
thread->SetMethodTraceBuffer(AcquireTraceBuffer(tid));
}
}
return;
}
void TraceWriter::FlushBuffer(uintptr_t* method_trace_entries,
size_t current_offset,
size_t tid,
const std::unordered_map<ArtMethod*, std::string>& method_infos) {
// Take a tracing_lock_ to serialize writes across threads. We also need to allocate a unique
// method id for each method. We do that by maintaining a map from id to method for each newly
// seen method. tracing_lock_ is required to serialize these.
MutexLock mu(Thread::Current(), tracing_lock_);
size_t current_index;
uint8_t* buffer_ptr = buf_.get();
size_t buffer_size = buffer_size_;
if (trace_output_mode_ == TraceOutputMode::kStreaming) {
// In streaming mode, we flush the data to file each time we flush the per-thread buffer.
// Just reuse the entire buffer.
current_index = 0;
} else {
// In non-streaming mode we only flush at the end, so retain the earlier data. If the buffer
// is full we don't process any more entries.
current_index = cur_offset_;
}
uint16_t thread_id = GetThreadEncoding(tid);
bool has_thread_cpu_clock = UseThreadCpuClock(clock_source_);
bool has_wall_clock = UseWallClock(clock_source_);
const size_t record_size = GetRecordSize(clock_source_);
DCHECK_LT(record_size, kPerThreadBufSize);
size_t num_entries = GetNumEntries(clock_source_);
size_t num_records = (kPerThreadBufSize - current_offset) / num_entries;
DCHECK_EQ((kPerThreadBufSize - current_offset) % num_entries, 0u);
// Check if there is sufficient place in the buffer for non-streaming case. If not return early.
if (cur_offset_ + record_size * num_records >= buffer_size &&
trace_output_mode_ != TraceOutputMode::kStreaming) {
overflow_ = true;
return;
}
DCHECK_GT(buffer_size_, record_size * num_entries);
for (size_t entry_index = kPerThreadBufSize; entry_index != current_offset;) {
entry_index -= num_entries;
size_t record_index = entry_index;
uintptr_t method_and_action = method_trace_entries[record_index++];
ArtMethod* method = reinterpret_cast<ArtMethod*>(method_and_action & kMaskTraceAction);
CHECK(method != nullptr);
TraceAction action = DecodeTraceAction(method_and_action);
uint32_t thread_time = 0;
uint32_t wall_time = 0;
if (has_thread_cpu_clock) {
thread_time = method_trace_entries[record_index++];
}
if (has_wall_clock) {
uint64_t timestamp = method_trace_entries[record_index++];
if (art::kRuntimePointerSize == PointerSize::k32) {
// On 32-bit architectures timestamp is stored as two 32-bit values.
uint64_t high_timestamp = method_trace_entries[record_index++];
timestamp = (high_timestamp << 32 | timestamp);
}
wall_time = GetMicroTime(timestamp) - start_time_;
}
auto [method_id, is_new_method] = GetMethodEncoding(method);
if (is_new_method && trace_output_mode_ == TraceOutputMode::kStreaming) {
RecordMethodInfo(method_infos.find(method)->second, method_id);
}
DCHECK_LT(current_index + record_size, buffer_size);
EncodeEventEntry(
buffer_ptr + current_index, thread_id, method_id, action, thread_time, wall_time);
current_index += record_size;
}
if (trace_output_mode_ == TraceOutputMode::kStreaming) {
// Flush the contents of buffer to file.
if (!trace_file_->WriteFully(buffer_ptr, current_index)) {
PLOG(WARNING) << "Failed streaming a tracing event.";
}
} else {
// In non-streaming mode, we keep the data in the buffer and write to the
// file when tracing has stopped. Just updated the offset of the buffer.
cur_offset_ = current_index;
}
return;
}
void Trace::LogMethodTraceEvent(Thread* thread,
ArtMethod* method,
TraceAction action,
uint32_t thread_clock_diff,
uint64_t timestamp_counter) {
// This method is called in both tracing modes (method and sampling). In sampling mode, this
// method is only called by the sampling thread. In method tracing mode, it can be called
// concurrently.
// In non-streaming modes, we stop recoding events once the buffer is full.
if (trace_writer_->HasOverflow()) {
return;
}
uintptr_t* method_trace_buffer = thread->GetMethodTraceBuffer();
size_t* current_index = thread->GetMethodTraceIndexPtr();
// Initialize the buffer lazily. It's just simpler to keep the creation at one place.
if (method_trace_buffer == nullptr) {
method_trace_buffer = trace_writer_->AcquireTraceBuffer(thread->GetTid());
DCHECK(method_trace_buffer != nullptr);
thread->SetMethodTraceBuffer(method_trace_buffer);
*current_index = kPerThreadBufSize;
trace_writer_->RecordThreadInfo(thread);
}
size_t required_entries = GetNumEntries(clock_source_);
if (*current_index < required_entries) {
// This returns nullptr in non-streaming mode if there's an overflow and we cannot record any
// more entries. In streaming mode, it returns nullptr if it fails to allocate a new buffer.
method_trace_buffer = trace_writer_->PrepareBufferForNewEntries(thread);
if (method_trace_buffer == nullptr) {
return;
}
}
// Record entry in per-thread trace buffer.
// Update the offset
int new_entry_index = *current_index - required_entries;
*current_index = new_entry_index;
// Ensure we always use the non-obsolete version of the method so that entry/exit events have the
// same pointer value.
method = method->GetNonObsoleteMethod();
method_trace_buffer[new_entry_index++] = reinterpret_cast<uintptr_t>(method) | action;
if (UseThreadCpuClock(clock_source_)) {
method_trace_buffer[new_entry_index++] = thread_clock_diff;
}
if (UseWallClock(clock_source_)) {
if (art::kRuntimePointerSize == PointerSize::k32) {
// On 32-bit architectures store timestamp counter as two 32-bit values.
method_trace_buffer[new_entry_index++] = static_cast<uint32_t>(timestamp_counter);
method_trace_buffer[new_entry_index++] = timestamp_counter >> 32;
} else {
method_trace_buffer[new_entry_index++] = timestamp_counter;
}
}
}
void TraceWriter::EncodeEventEntry(uint8_t* ptr,
uint16_t thread_id,
uint32_t method_index,
TraceAction action,
uint32_t thread_clock_diff,
uint32_t wall_clock_diff) {
static constexpr size_t kPacketSize = 14U; // The maximum size of data in a packet.
DCHECK(method_index < (1 << (32 - TraceActionBits)));
uint32_t method_value = (method_index << TraceActionBits) | action;
Append2LE(ptr, thread_id);
Append4LE(ptr + 2, method_value);
ptr += 6;
if (UseThreadCpuClock(clock_source_)) {
Append4LE(ptr, thread_clock_diff);
ptr += 4;
}
if (UseWallClock(clock_source_)) {
Append4LE(ptr, wall_clock_diff);
}
static_assert(kPacketSize == 2 + 4 + 4 + 4, "Packet size incorrect.");
}
void TraceWriter::EnsureSpace(uint8_t* buffer,
size_t* current_index,
size_t buffer_size,
size_t required_size) {
if (*current_index + required_size < buffer_size) {
return;
}
if (!trace_file_->WriteFully(buffer, *current_index)) {
PLOG(WARNING) << "Failed streaming a tracing event.";
}
*current_index = 0;
}
void TraceWriter::DumpMethodList(std::ostream& os) {
MutexLock mu(Thread::Current(), tracing_lock_);
for (auto const& entry : art_method_id_map_) {
os << GetMethodLine(GetMethodInfoLine(entry.first), entry.second);
}
}
void TraceWriter::DumpThreadList(std::ostream& os) {
MutexLock mu(Thread::Current(), tracing_lock_);
for (const auto& it : threads_list_) {
os << it.first << "\t" << it.second << "\n";
}
}
TraceOutputMode Trace::GetOutputMode() {
MutexLock mu(Thread::Current(), *Locks::trace_lock_);
CHECK(the_trace_ != nullptr) << "Trace output mode requested, but no trace currently running";
return the_trace_->trace_writer_->GetOutputMode();
}
Trace::TraceMode Trace::GetMode() {
MutexLock mu(Thread::Current(), *Locks::trace_lock_);
CHECK(the_trace_ != nullptr) << "Trace mode requested, but no trace currently running";
return the_trace_->trace_mode_;
}
int Trace::GetFlags() {
MutexLock mu(Thread::Current(), *Locks::trace_lock_);
CHECK(the_trace_ != nullptr) << "Trace flags requested, but no trace currently running";
return the_trace_->flags_;
}
int Trace::GetIntervalInMillis() {
MutexLock mu(Thread::Current(), *Locks::trace_lock_);
CHECK(the_trace_ != nullptr) << "Trace interval requested, but no trace currently running";
return the_trace_->interval_us_;
}
size_t Trace::GetBufferSize() {
MutexLock mu(Thread::Current(), *Locks::trace_lock_);
CHECK(the_trace_ != nullptr) << "Trace buffer size requested, but no trace currently running";
return the_trace_->trace_writer_->GetBufferSize();
}
bool Trace::IsTracingEnabled() {
MutexLock mu(Thread::Current(), *Locks::trace_lock_);
return the_trace_ != nullptr;
}
} // namespace art