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Merged
jbachorik merged 2 commits into from
Mar 21, 2026
Merged

Port async-profiler#1701: optimize nmethod type checks #423

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40950e6
Port async-profiler#1701: optimize nmethod type checks
jbachorik Mar 19, 2026
0cf5358
Move startsWith to file-scope inline utility
jbachorik Mar 21, 2026
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4 changes: 3 additions & 1 deletion ddprof-lib/src/main/cpp/profiler.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -96,7 +96,9 @@ void Profiler::addRuntimeStub(const void *address, int length,
_runtime_stubs.add(address, length, name, true);
_stubs_lock.unlock();

if (strcmp(name, "call_stub") == 0) {
if (name[0] == 'I' && strcmp(name, "Interpreter") == 0) {
CodeHeap::setInterpreterStart(address);
} else if (strcmp(name, "call_stub") == 0) {
_call_stub_begin = address;
_call_stub_end = (const char *)address + length;
}
Expand Down
94 changes: 47 additions & 47 deletions ddprof-lib/src/main/cpp/stackWalker.cpp
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Expand Up @@ -394,7 +394,53 @@ __attribute__((no_sanitize("address"))) int StackWalker::walkVM(void* ucontext,
anchor = NULL;
}

if (nm->isNMethod()) {
if (nm->isInterpreter()) {
if (vm_thread != NULL && vm_thread->inDeopt()) {
fillFrame(frames[depth++], BCI_ERROR, "break_deopt");
break;
}

bool is_plausible_interpreter_frame = StackWalkValidation::isPlausibleInterpreterFrame(fp, sp, bcp_offset);
if (is_plausible_interpreter_frame) {
VMMethod* method = ((VMMethod**)fp)[InterpreterFrame::method_offset];
jmethodID method_id = getMethodId(method);
if (method_id != NULL) {
Counters::increment(WALKVM_JAVA_FRAME_OK);
const char* bytecode_start = method->bytecode();
const char* bcp = ((const char**)fp)[bcp_offset];
int bci = bytecode_start == NULL || bcp < bytecode_start ? 0 : bcp - bytecode_start;
fillFrame(frames[depth++], FRAME_INTERPRETED, bci, method_id);

sp = ((uintptr_t*)fp)[InterpreterFrame::sender_sp_offset];
pc = stripPointer(((void**)fp)[FRAME_PC_SLOT]);
fp = *(uintptr_t*)fp;
continue;
}
}

if (depth == 0) {
VMMethod* method = (VMMethod*)frame.method();
jmethodID method_id = getMethodId(method);
if (method_id != NULL) {
Counters::increment(WALKVM_JAVA_FRAME_OK);
fillFrame(frames[depth++], FRAME_INTERPRETED, 0, method_id);

if (is_plausible_interpreter_frame) {
pc = stripPointer(((void**)fp)[FRAME_PC_SLOT]);
sp = frame.senderSP();
fp = *(uintptr_t*)fp;
} else {
pc = stripPointer(SafeAccess::load((void**)sp));
sp = frame.senderSP();
}
continue;
}
}

Counters::increment(WALKVM_BREAK_INTERPRETED);
fillFrame(frames[depth++], BCI_ERROR, "break_interpreted");
break;
} else if (nm->isNMethod()) {
// Check if deoptimization is in progress before walking compiled frames
if (vm_thread != NULL && vm_thread->inDeopt()) {
fillFrame(frames[depth++], BCI_ERROR, "break_deopt_compiled");
Expand Down Expand Up @@ -453,52 +499,6 @@ __attribute__((no_sanitize("address"))) int StackWalker::walkVM(void* ucontext,
Counters::increment(WALKVM_BREAK_COMPILED);
fillFrame(frames[depth++], BCI_ERROR, "break_compiled");
break;
} else if (nm->isInterpreter()) {
if (vm_thread != NULL && vm_thread->inDeopt()) {
fillFrame(frames[depth++], BCI_ERROR, "break_deopt");
break;
}

bool is_plausible_interpreter_frame = StackWalkValidation::isPlausibleInterpreterFrame(fp, sp, bcp_offset);
if (is_plausible_interpreter_frame) {
VMMethod* method = ((VMMethod**)fp)[InterpreterFrame::method_offset];
jmethodID method_id = getMethodId(method);
if (method_id != NULL) {
Counters::increment(WALKVM_JAVA_FRAME_OK);
const char* bytecode_start = method->bytecode();
const char* bcp = ((const char**)fp)[bcp_offset];
int bci = bytecode_start == NULL || bcp < bytecode_start ? 0 : bcp - bytecode_start;
fillFrame(frames[depth++], FRAME_INTERPRETED, bci, method_id);

sp = ((uintptr_t*)fp)[InterpreterFrame::sender_sp_offset];
pc = stripPointer(((void**)fp)[FRAME_PC_SLOT]);
fp = *(uintptr_t*)fp;
continue;
}
}

if (depth == 0) {
VMMethod* method = (VMMethod*)frame.method();
jmethodID method_id = getMethodId(method);
if (method_id != NULL) {
Counters::increment(WALKVM_JAVA_FRAME_OK);
fillFrame(frames[depth++], FRAME_INTERPRETED, 0, method_id);

if (is_plausible_interpreter_frame) {
pc = stripPointer(((void**)fp)[FRAME_PC_SLOT]);
sp = frame.senderSP();
fp = *(uintptr_t*)fp;
} else {
pc = stripPointer(SafeAccess::load((void**)sp));
sp = frame.senderSP();
}
continue;
}
}

Counters::increment(WALKVM_BREAK_INTERPRETED);
fillFrame(frames[depth++], BCI_ERROR, "break_interpreted");
break;
} else if (nm->isEntryFrame(pc) && !features.mixed) {
VMJavaFrameAnchor* next_anchor = VMJavaFrameAnchor::fromEntryFrame(fp);
if (next_anchor == NULL) {
Expand Down
6 changes: 6 additions & 0 deletions ddprof-lib/src/main/cpp/vmStructs.cpp
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Expand Up @@ -4,6 +4,7 @@
*/

#include <pthread.h>
#include <string.h>
#include <unistd.h>
#include <stdarg.h>
#include "vmStructs.h"
Expand Down Expand Up @@ -33,6 +34,8 @@ int VMStructs::_narrow_klass_shift = -1;
int VMStructs::_interpreter_frame_bcp_offset = 0;
unsigned char VMStructs::_unsigned5_base = 0;
const void* VMStructs::_call_stub_return = nullptr;
const void* VMStructs::_interpreter_start = nullptr;
VMNMethod* VMStructs::_interpreter_nm = nullptr;
const void* VMStructs::_interpreted_frame_valid_start = nullptr;
const void* VMStructs::_interpreted_frame_valid_end = nullptr;

Expand Down Expand Up @@ -437,6 +440,9 @@ void VMStructs::resolveOffsets() {
_heap_block_used_offset < 0) {
memset(_code_heap, 0, sizeof(_code_heap));
}
if (_interpreter_nm == NULL && _interpreter_start != NULL) {
_interpreter_nm = CodeHeap::findNMethod(_interpreter_start);
}
}

void VMStructs::initJvmFunctions() {
Expand Down
32 changes: 24 additions & 8 deletions ddprof-lib/src/main/cpp/vmStructs.h
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Expand Up @@ -10,7 +10,6 @@
#include <initializer_list>
#include <jvmti.h>
#include <stdint.h>
#include <string.h>
#include <type_traits>
#include "codeCache.h"
#include "counters.h"
Expand All @@ -21,6 +20,7 @@

class GCHeapSummary;
class HeapUsage;
class VMNMethod;


// During stack walking in the profiler's signal handler, GC or class unloading
Expand Down Expand Up @@ -310,6 +310,8 @@ class VMStructs {
static int _interpreter_frame_bcp_offset;
static unsigned char _unsigned5_base;
static const void* _call_stub_return;
static const void* _interpreter_start;
static VMNMethod* _interpreter_nm;
static const void* _interpreted_frame_valid_start;
static const void* _interpreted_frame_valid_end;

Expand Down Expand Up @@ -829,6 +831,16 @@ DECLARE(VMMethod)
DECLARE_END

DECLARE(VMNMethod)
private:
// Inline string comparison to avoid indirect call to strncmp
template<size_t N>
static bool startsWith(const char* s, const char (&pattern)[N]) {

@zhengyu123 zhengyu123 Mar 20, 2026

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Make it an inline utility function.

@jbachorik jbachorik Mar 21, 2026

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Moved startsWith to a file-scope static inline utility function just before DECLARE(VMNMethod).

for (size_t i = 0; i < N - 1; i++) {
if (s[i] != pattern[i]) return false;
}
return true;
}

public:
int size() {
assert(_blob_size_offset >= 0);
Expand Down Expand Up @@ -902,24 +914,23 @@ DECLARE(VMNMethod)
return *(const char**) at(_nmethod_name_offset);
}

bool isNMethod() {
const char* n = name();
return n != NULL && (strcmp(n, "nmethod") == 0 || strcmp(n, "native nmethod") == 0);
bool isInterpreter() {
return this == _interpreter_nm;
}

bool isInterpreter() {
bool isNMethod() {
const char* n = name();
return n != NULL && strcmp(n, "Interpreter") == 0;
return n != NULL && (startsWith(n, "nmethod\0") || startsWith(n, "native nmethod\0"));
}

bool isStub() {
const char* n = name();
return n != NULL && strncmp(n, "StubRoutines", 12) == 0;
return n != NULL && startsWith(n, "StubRoutines");
}

bool isVTableStub() {
const char* n = name();
return n != NULL && strcmp(n, "vtable chunks") == 0;
return n != NULL && startsWith(n, "vtable chunks");
}

VMMethod* method() {
Expand Down Expand Up @@ -985,6 +996,11 @@ class CodeHeap : VMStructs {
high = _code_heap_high);
}

static void setInterpreterStart(const void* start) {
_interpreter_start = start;
_interpreter_nm = findNMethod(start);
}

static VMNMethod* findNMethod(const void* pc) {
if (contains(_code_heap[0], pc)) return findNMethod(_code_heap[0], pc);
if (contains(_code_heap[1], pc)) return findNMethod(_code_heap[1], pc);
Expand Down
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