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Implement support for providing information to Linux's perf JIT interface. 

For more information on what this is, see:
 https://github.com/torvalds/linux/blob/master/tools/perf/Documentation/jit-interface.txt

[ChangeLog][QtQml][Profiling] QtQml can now write additional information so that
perf is able to give function names of JavaScript methods when profiling. To
enable this, set the environment variable QV4_PROFILE_WRITE_PERF_MAP=1 when
running the process in question.

Change-Id: I187c9b0792f40d93c89a986c0edb3c4487095cb7
Reviewed-by: Ulf Hermann <ulf.hermann@theqtcompany.com>
This commit is contained in:
Robin Burchell 2015-07-28 12:41:31 +00:00
parent 6328dd2d27
commit 45ea8df187
1 changed files with 61 additions and 1 deletions
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62
src/qml/jit/qv4isel_masm.cpp
View File

@ -45,6 +45,7 @@
#include "qv4binop_p.h"
#include <QtCore/QBuffer>
#include <QtCore/QCoreApplication>
#include <assembler/LinkBuffer.h>
#include <WTFStubs.h>
@ -120,6 +121,19 @@ static void printDisassembledOutputWithCalls(QByteArray processedOutput, const Q
qDebug("%s", processedOutput.constData());
}
#if defined(Q_OS_LINUX)
static FILE *pmap;
static void qt_closePmap()
{
if (pmap) {
fclose(pmap);
pmap = 0;
}
}
#endif
JSC::MacroAssemblerCodeRef Assembler::link(int *codeSize)
{
Label endOfCode = label();
@ -167,6 +181,8 @@ JSC::MacroAssemblerCodeRef Assembler::link(int *codeSize)
*codeSize = linkBuffer.offsetOf(endOfCode);
QByteArray name;
JSC::MacroAssemblerCodeRef codeRef;
static bool showCode = !qgetenv("QV4_SHOW_ASM").isNull();
@ -175,7 +191,7 @@ JSC::MacroAssemblerCodeRef Assembler::link(int *codeSize)
buf.open(QIODevice::WriteOnly);
WTF::setDataFile(new QIODevicePrintStream(&buf));
QByteArray name = _function->name->toUtf8();
name = _function->name->toUtf8();
if (name.isEmpty()) {
name = QByteArray::number(quintptr(_function), 16);
name.prepend("IR::Function(0x");
@ -189,6 +205,50 @@ JSC::MacroAssemblerCodeRef Assembler::link(int *codeSize)
codeRef = linkBuffer.finalizeCodeWithoutDisassembly();
}
#if defined(Q_OS_LINUX)
// This implements writing of JIT'd addresses so that perf can find the
// symbol names.
//
// Perf expects the mapping to be in a certain place and have certain
// content, for more information, see:
// https://github.com/torvalds/linux/blob/master/tools/perf/Documentation/jit-interface.txt
static bool doProfile = !qEnvironmentVariableIsEmpty("QV4_PROFILE_WRITE_PERF_MAP");
static bool profileInitialized = false;
if (doProfile && !profileInitialized) {
profileInitialized = true;
char pname[PATH_MAX];
snprintf(pname, PATH_MAX - 1, "/tmp/perf-%lu.map",
(unsigned long)QCoreApplication::applicationPid());
pmap = fopen(pname, "w");
if (!pmap)
qWarning("QV4: Can't write %s, call stacks will not contain JavaScript function names", pname);
// make sure we clean up nicely
std::atexit(qt_closePmap);
}
if (pmap) {
// this may have been pre-populated, if QV4_SHOW_ASM was on
if (name.isEmpty()) {
name = _function->name->toUtf8();
if (name.isEmpty()) {
name = QByteArray::number(quintptr(_function), 16);
name.prepend("IR::Function(0x");
name.append(")");
}
}
fprintf(pmap, "%llx %x %.*s\n",
(long long unsigned int)codeRef.code().executableAddress(),
*codeSize,
name.length(),
name.constData());
fflush(pmap);
}
#endif
return codeRef;
}