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gh-118518: Allow perf to work without frame pointers (#112254)

This commit is contained in:
Pablo Galindo Salgado 2024-05-05 03:07:29 +02:00 committed by GitHub
parent 999f0c5122
commit 1b22d801b8
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19 changed files with 892 additions and 39 deletions
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5
Doc/c-api/init_config.rst
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@ -1251,7 +1251,10 @@ PyConfig
for more information.
Set by :option:`-X perf <-X>` command line option and by the
:envvar:`PYTHONPERFSUPPORT` environment variable.
:envvar:`PYTHONPERFSUPPORT` environment variable for perf support
with stack pointers and :option:`-X perfjit <-X>` command line option
and by the :envvar:`PYTHONPERFJITSUPPORT` environment variable for perf
support with DWARF JIT information.
Default: ``-1``.

33
Doc/howto/perf_profiling.rst
View File

@ -205,3 +205,36 @@ You can check if your system has been compiled with this flag by running::
If you don't see any output it means that your interpreter has not been compiled with
frame pointers and therefore it may not be able to show Python functions in the output
of ``perf``.
How to work without frame pointers
----------------------------------
If you are working with a Python interpreter that has been compiled without frame pointers
you can still use the ``perf`` profiler but the overhead will be a bit higher because Python
needs to generate unwinding information for every Python function call on the fly. Additionally,
``perf`` will take more time to process the data because it will need to use the DWARF debugging
information to unwind the stack and this is a slow process.
To enable this mode, you can use the environment variable :envvar:`PYTHONPERFJITSUPPORT` or the
:option:`-X perfjit <-X>` option, which will enable the JIT mode for the ``perf`` profiler.
When using the perf JIT mode, you need an extra step before you can run ``perf report``. You need to
call the ``perf inject`` command to inject the JIT information into the ``perf.data`` file.
$ perf record -F 9999 -g --call-graph dwarf -o perf.data python -Xperfjit my_script.py
$ perf inject -i perf.data --jit
$ perf report -g -i perf.data
or using the environment variable::
$ PYTHONPERFJITSUPPORT=1 perf record -F 9999 -g --call-graph dwarf -o perf.data python my_script.py
$ perf inject -i perf.data --jit
$ perf report -g -i perf.data
Notice that when using ``--call-graph dwarf`` the ``perf`` tool will take snapshots of the stack of
the process being profiled and save the information in the ``perf.data`` file. By default the size of
the stack dump is 8192 bytes but the user can change the size by passing the size after comma like
``--call-graph dwarf,4096``. The size of the stack dump is important because if the size is too small
``perf`` will not be able to unwind the stack and the output will be incomplete.

24
Doc/using/cmdline.rst
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@ -586,6 +586,15 @@ Miscellaneous options
.. versionadded:: 3.12
* ``-X perfjit`` enables support for the Linux ``perf`` profiler with DWARF
support. When this option is provided, the ``perf`` profiler will be able
to report Python calls using DWARF ifnormation. This option is only available on
some platforms and will do nothing if is not supported on the current
system. The default value is "off". See also :envvar:`PYTHONPERFJITSUPPORT`
and :ref:`perf_profiling`.
.. versionadded:: 3.13
* :samp:`-X cpu_count={n}` overrides :func:`os.cpu_count`,
:func:`os.process_cpu_count`, and :func:`multiprocessing.cpu_count`.
*n* must be greater than or equal to 1.
@ -1127,6 +1136,21 @@ conflict.
.. versionadded:: 3.12
.. envvar:: PYTHONPERFJITSUPPORT
If this variable is set to a nonzero value, it enables support for
the Linux ``perf`` profiler so Python calls can be detected by it
using DWARF information.
If set to ``0``, disable Linux ``perf`` profiler support.
See also the :option:`-X perfjit <-X>` command-line option
and :ref:`perf_profiling`.
.. versionadded:: 3.13
.. envvar:: PYTHON_CPU_COUNT
If this variable is set to a positive integer, it overrides the return

5
Doc/whatsnew/3.13.rst
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@ -231,6 +231,11 @@ Other Language Changes
equivalent of the :option:`-X frozen_modules <-X>` command-line option.
(Contributed by Yilei Yang in :gh:`111374`.)
* Add :ref:`support for the perf profiler <perf_profiling>` working without
frame pointers through the new environment variable
:envvar:`PYTHONPERFJITSUPPORT` and command-line option :option:`-X perfjit
<-X>` (Contributed by Pablo Galindo in :gh:`118518`.)
* The new :envvar:`PYTHON_HISTORY` environment variable can be used to change
the location of a ``.python_history`` file.
(Contributed by Levi Sabah, Zackery Spytz and Hugo van Kemenade in

1
Include/internal/pycore_ceval.h
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@ -108,6 +108,7 @@ extern int _PyIsPerfTrampolineActive(void);
extern PyStatus _PyPerfTrampoline_AfterFork_Child(void);
#ifdef PY_HAVE_PERF_TRAMPOLINE
extern _PyPerf_Callbacks _Py_perfmap_callbacks;
extern _PyPerf_Callbacks _Py_perfmap_jit_callbacks;
#endif
static inline PyObject*

2
Include/internal/pycore_ceval_state.h
View File

@ -75,6 +75,7 @@ struct trampoline_api_st {
unsigned int code_size, PyCodeObject* code);
int (*free_state)(void* state);
void *state;
Py_ssize_t code_padding;
};
#endif
@ -83,6 +84,7 @@ struct _ceval_runtime_state {
struct {
#ifdef PY_HAVE_PERF_TRAMPOLINE
perf_status_t status;
int perf_trampoline_type;
Py_ssize_t extra_code_index;
struct code_arena_st *code_arena;
struct trampoline_api_st trampoline_api;

146
Lib/test/test_perf_profiler.py
View File

@ -5,6 +5,7 @@ import sys
import sysconfig
import os
import pathlib
import shutil
from test import support
from test.support.script_helper import (
make_script,
@ -76,14 +77,27 @@ class TestPerfTrampoline(unittest.TestCase):
perf_file = pathlib.Path(f"/tmp/perf-{process.pid}.map")
self.assertTrue(perf_file.exists())
perf_file_contents = perf_file.read_text()
perf_lines = perf_file_contents.splitlines();
expected_symbols = [f"py::foo:{script}", f"py::bar:{script}", f"py::baz:{script}"]
perf_lines = perf_file_contents.splitlines()
expected_symbols = [
f"py::foo:{script}",
f"py::bar:{script}",
f"py::baz:{script}",
]
for expected_symbol in expected_symbols:
perf_line = next((line for line in perf_lines if expected_symbol in line), None)
self.assertIsNotNone(perf_line, f"Could not find {expected_symbol} in perf file")
perf_line = next(
(line for line in perf_lines if expected_symbol in line), None
)
self.assertIsNotNone(
perf_line, f"Could not find {expected_symbol} in perf file"
)
perf_addr = perf_line.split(" ")[0]
self.assertFalse(perf_addr.startswith("0x"), "Address should not be prefixed with 0x")
self.assertTrue(set(perf_addr).issubset(string.hexdigits), "Address should contain only hex characters")
self.assertFalse(
perf_addr.startswith("0x"), "Address should not be prefixed with 0x"
)
self.assertTrue(
set(perf_addr).issubset(string.hexdigits),
"Address should contain only hex characters",
)
def test_trampoline_works_with_forks(self):
code = """if 1:
@ -212,7 +226,7 @@ class TestPerfTrampoline(unittest.TestCase):
assert_python_ok("-c", code)
def is_unwinding_reliable():
def is_unwinding_reliable_with_frame_pointers():
cflags = sysconfig.get_config_var("PY_CORE_CFLAGS")
if not cflags:
return False
@ -259,14 +273,27 @@ def perf_command_works():
return True
def run_perf(cwd, *args, **env_vars):
def run_perf(cwd, *args, use_jit=False, **env_vars):
if env_vars:
env = os.environ.copy()
env.update(env_vars)
else:
env = None
output_file = cwd + "/perf_output.perf"
base_cmd = ("perf", "record", "-g", "--call-graph=fp", "-o", output_file, "--")
if not use_jit:
base_cmd = ("perf", "record", "-g", "--call-graph=fp", "-o", output_file, "--")
else:
base_cmd = (
"perf",
"record",
"-g",
"--call-graph=dwarf,65528",
"-F99",
"-k1",
"-o",
output_file,
"--",
)
proc = subprocess.run(
base_cmd + args,
stdout=subprocess.PIPE,
@ -274,9 +301,21 @@ def run_perf(cwd, *args, **env_vars):
env=env,
)
if proc.returncode:
print(proc.stderr)
print(proc.stderr, file=sys.stderr)
raise ValueError(f"Perf failed with return code {proc.returncode}")
if use_jit:
jit_output_file = cwd + "/jit_output.dump"
command = ("perf", "inject", "-j", "-i", output_file, "-o", jit_output_file)
proc = subprocess.run(
command, stderr=subprocess.PIPE, stdout=subprocess.PIPE, env=env
)
if proc.returncode:
print(proc.stderr)
raise ValueError(f"Perf failed with return code {proc.returncode}")
# Copy the jit_output_file to the output_file
os.rename(jit_output_file, output_file)
base_cmd = ("perf", "script")
proc = subprocess.run(
("perf", "script", "-i", output_file),
@ -290,20 +329,9 @@ def run_perf(cwd, *args, **env_vars):
)
@unittest.skipUnless(perf_command_works(), "perf command doesn't work")
@unittest.skipUnless(is_unwinding_reliable(), "Unwinding is unreliable")
class TestPerfProfiler(unittest.TestCase):
def setUp(self):
super().setUp()
self.perf_files = set(pathlib.Path("/tmp/").glob("perf-*.map"))
def tearDown(self) -> None:
super().tearDown()
files_to_delete = (
set(pathlib.Path("/tmp/").glob("perf-*.map")) - self.perf_files
)
for file in files_to_delete:
file.unlink()
class TestPerfProfilerMixin:
def run_perf(self, script_dir, perf_mode, script):
raise NotImplementedError()
def test_python_calls_appear_in_the_stack_if_perf_activated(self):
with temp_dir() as script_dir:
@ -322,14 +350,14 @@ class TestPerfProfiler(unittest.TestCase):
baz(10000000)
"""
script = make_script(script_dir, "perftest", code)
stdout, stderr = run_perf(script_dir, sys.executable, "-Xperf", script)
stdout, stderr = self.run_perf(script_dir, script)
self.assertEqual(stderr, "")
self.assertIn(f"py::foo:{script}", stdout)
self.assertIn(f"py::bar:{script}", stdout)
self.assertIn(f"py::baz:{script}", stdout)
def test_python_calls_do_not_appear_in_the_stack_if_perf_activated(self):
def test_python_calls_do_not_appear_in_the_stack_if_perf_deactivated(self):
with temp_dir() as script_dir:
code = """if 1:
def foo(n):
@ -346,13 +374,38 @@ class TestPerfProfiler(unittest.TestCase):
baz(10000000)
"""
script = make_script(script_dir, "perftest", code)
stdout, stderr = run_perf(script_dir, sys.executable, script)
stdout, stderr = self.run_perf(
script_dir, script, activate_trampoline=False
)
self.assertEqual(stderr, "")
self.assertNotIn(f"py::foo:{script}", stdout)
self.assertNotIn(f"py::bar:{script}", stdout)
self.assertNotIn(f"py::baz:{script}", stdout)
@unittest.skipUnless(perf_command_works(), "perf command doesn't work")
@unittest.skipUnless(
is_unwinding_reliable_with_frame_pointers(),
"Unwinding is unreliable with frame pointers",
)
class TestPerfProfiler(unittest.TestCase, TestPerfProfilerMixin):
def run_perf(self, script_dir, script, activate_trampoline=True):
if activate_trampoline:
return run_perf(script_dir, sys.executable, "-Xperf", script)
return run_perf(script_dir, sys.executable, script)
def setUp(self):
super().setUp()
self.perf_files = set(pathlib.Path("/tmp/").glob("perf-*.map"))
def tearDown(self) -> None:
super().tearDown()
files_to_delete = (
set(pathlib.Path("/tmp/").glob("perf-*.map")) - self.perf_files
)
for file in files_to_delete:
file.unlink()
def test_pre_fork_compile(self):
code = """if 1:
import sys
@ -370,7 +423,7 @@ class TestPerfProfiler(unittest.TestCase):
foo_fork()
def foo():
pass
import time; time.sleep(1)
def bar():
foo()
@ -423,12 +476,41 @@ class TestPerfProfiler(unittest.TestCase):
# identical in both the parent and child perf-map files.
perf_file_lines = perf_file_contents.split("\n")
for line in perf_file_lines:
if (
f"py::foo_fork:{script}" in line
or f"py::bar_fork:{script}" in line
):
if f"py::foo_fork:{script}" in line or f"py::bar_fork:{script}" in line:
self.assertIn(line, child_perf_file_contents)
def _is_kernel_version_at_least(major, minor):
try:
with open("/proc/version") as f:
version = f.readline().split()[2]
except FileNotFoundError:
return False
version = version.split(".")
return int(version[0]) > major or (int(version[0]) == major and int(version[1]) >= minor)
@unittest.skipUnless(perf_command_works(), "perf command doesn't work")
@unittest.skipUnless(_is_kernel_version_at_least(6, 6), "perf command may not work due to a perf bug")
class TestPerfProfilerWithDwarf(unittest.TestCase, TestPerfProfilerMixin):
def run_perf(self, script_dir, script, activate_trampoline=True):
if activate_trampoline:
return run_perf(
script_dir, sys.executable, "-Xperfjit", script, use_jit=True
)
return run_perf(script_dir, sys.executable, script, use_jit=True)
def setUp(self):
super().setUp()
self.perf_files = set(pathlib.Path("/tmp/").glob("jit*.dump"))
self.perf_files |= set(pathlib.Path("/tmp/").glob("jitted-*.so"))
def tearDown(self) -> None:
super().tearDown()
files_to_delete = set(pathlib.Path("/tmp/").glob("jit*.dump"))
files_to_delete |= set(pathlib.Path("/tmp/").glob("jitted-*.so"))
files_to_delete = files_to_delete - self.perf_files
for file in files_to_delete:
file.unlink()
if __name__ == "__main__":
unittest.main()

1
Makefile.pre.in
View File

@ -488,6 +488,7 @@ PYTHON_OBJS= \
Python/fileutils.o \
Python/suggestions.o \
Python/perf_trampoline.o \
Python/perf_jit_trampoline.o \
Python/$(DYNLOADFILE) \
$(LIBOBJS) \
$(MACHDEP_OBJS) \

4
Misc/NEWS.d/next/Core and Builtins/2024-05-02-20-32-42.gh-issue-118518.m-JbTi.rst Normal file
View File

@ -0,0 +1,4 @@
Allow the Linux perf support to work without frame pointers using perf's
advanced JIT support. The feature is activated when using the
``PYTHONPERFJITSUPPORT`` environment variable or when running Python with
``-Xperfjit``. Patch by Pablo Galindo

1
PCbuild/_freeze_module.vcxproj
View File

@ -240,6 +240,7 @@
<ClCompile Include="..\Python\parking_lot.c" />
<ClCompile Include="..\Python\pathconfig.c" />
<ClCompile Include="..\Python\perf_trampoline.c" />
<ClCompile Include="..\Python\perf_jit_trampoline.c" />
<ClCompile Include="..\Python\preconfig.c" />
<ClCompile Include="..\Python\pyarena.c" />
<ClCompile Include="..\Python\pyctype.c" />

3
PCbuild/_freeze_module.vcxproj.filters
View File

@ -94,6 +94,9 @@
<ClCompile Include="..\Python\perf_trampoline.c">
<Filter>Source Files</Filter>
</ClCompile>
<ClCompile Include="..\Python\perf_jit_trampoline.c">
<Filter>Source Files</Filter>
</ClCompile>
<ClCompile Include="..\Python\compile.c">
<Filter>Source Files</Filter>
</ClCompile>

1
PCbuild/pythoncore.vcxproj
View File

@ -609,6 +609,7 @@
<ClCompile Include="..\Python\parking_lot.c" />
<ClCompile Include="..\Python\pathconfig.c" />
<ClCompile Include="..\Python\perf_trampoline.c" />
<ClCompile Include="..\Python\perf_jit_trampoline.c" />
<ClCompile Include="..\Python\preconfig.c" />
<ClCompile Include="..\Python\pyarena.c" />
<ClCompile Include="..\Python\pyctype.c" />

3
PCbuild/pythoncore.vcxproj.filters
View File

@ -1403,6 +1403,9 @@
<ClCompile Include="..\Python\perf_trampoline.c">
<Filter>Python</Filter>
</ClCompile>
<ClCompile Include="..\Python\perf_jit_trampoline.c">
<Filter>Python</Filter>
</ClCompile>
<ClCompile Include="..\Python\preconfig.c">
<Filter>Python</Filter>
</ClCompile>

14
Python/initconfig.c
View File

@ -1703,6 +1703,20 @@ config_init_perf_profiling(PyConfig *config)
if (xoption) {
config->perf_profiling = 1;
}
env = config_get_env(config, "PYTHONPERFJITSUPPORT");
if (env) {
if (_Py_str_to_int(env, &active) != 0) {
active = 0;
}
if (active) {
config->perf_profiling = 2;
}
}
xoption = config_get_xoption(config, L"perfjit");
if (xoption) {
config->perf_profiling = 2;
}
return _PyStatus_OK();
}

615
Python/perf_jit_trampoline.c Normal file
View File

@ -0,0 +1,615 @@
#include "Python.h"
#include "pycore_ceval.h" // _PyPerf_Callbacks
#include "pycore_frame.h"
#include "pycore_interp.h"
#ifdef PY_HAVE_PERF_TRAMPOLINE
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h> // mmap()
#include <sys/types.h>
#include <unistd.h> // sysconf()
#include <sys/time.h> // gettimeofday()
// ----------------------------------
// Perf jitdump API
// ----------------------------------
typedef struct {
FILE* perf_map;
PyThread_type_lock map_lock;
void* mapped_buffer;
size_t mapped_size;
int code_id;
} PerfMapJitState;
static PerfMapJitState perf_jit_map_state;
/*
Usually the binary and libraries are mapped in separate region like below:
address ->
--+---------------------+--//--+---------------------+--
| .text | .data | ... | | .text | .data | ... |
--+---------------------+--//--+---------------------+--
myprog libc.so
So it'd be easy and straight-forward to find a mapped binary or library from an
address.
But for JIT code, the code arena only cares about the code section. But the
resulting DSOs (which is generated by perf inject -j) contain ELF headers and
unwind info too. Then it'd generate following address space with synthesized
MMAP events. Let's say it has a sample between address B and C.
sample
|
address -> A B v C
---------------------------------------------------------------------------------------------------
/tmp/jitted-PID-0.so | (headers) | .text | unwind info |
/tmp/jitted-PID-1.so | (headers) | .text | unwind info |
/tmp/jitted-PID-2.so | (headers) | .text | unwind info |
...
---------------------------------------------------------------------------------------------------
If it only maps the .text section, it'd find the jitted-PID-1.so but cannot see
the unwind info. If it maps both .text section and unwind sections, the sample
could be mapped to either jitted-PID-0.so or jitted-PID-1.so and it's confusing
which one is right. So to make perf happy we have non-overlapping ranges for each
DSO:
address ->
-------------------------------------------------------------------------------------------------------
/tmp/jitted-PID-0.so | (headers) | .text | unwind info |
/tmp/jitted-PID-1.so | (headers) | .text | unwind info |
/tmp/jitted-PID-2.so | (headers) | .text | unwind info |
...
-------------------------------------------------------------------------------------------------------
As the trampolines are constant, we add a constant padding but in general the padding needs to have the
size of the unwind info rounded to 16 bytes. In general, for our trampolines this is 0x50
*/
#define PERF_JIT_CODE_PADDING 0x100
#define trampoline_api _PyRuntime.ceval.perf.trampoline_api
typedef uint64_t uword;
typedef const char* CodeComments;
#define Pd "d"
#define MB (1024 * 1024)
#define EM_386 3
#define EM_X86_64 62
#define EM_ARM 40
#define EM_AARCH64 183
#define EM_RISCV 243
#define TARGET_ARCH_IA32 0
#define TARGET_ARCH_X64 0
#define TARGET_ARCH_ARM 0
#define TARGET_ARCH_ARM64 0
#define TARGET_ARCH_RISCV32 0
#define TARGET_ARCH_RISCV64 0
#define FLAG_generate_perf_jitdump 0
#define FLAG_write_protect_code 0
#define FLAG_write_protect_vm_isolate 0
#define FLAG_code_comments 0
#define UNREACHABLE()
static uword GetElfMachineArchitecture(void) {
#if TARGET_ARCH_IA32
return EM_386;
#elif TARGET_ARCH_X64
return EM_X86_64;
#elif TARGET_ARCH_ARM
return EM_ARM;
#elif TARGET_ARCH_ARM64
return EM_AARCH64;
#elif TARGET_ARCH_RISCV32 || TARGET_ARCH_RISCV64
return EM_RISCV;
#else
UNREACHABLE();
return 0;
#endif
}
typedef struct {
uint32_t magic;
uint32_t version;
uint32_t size;
uint32_t elf_mach_target;
uint32_t reserved;
uint32_t process_id;
uint64_t time_stamp;
uint64_t flags;
} Header;
enum PerfEvent {
PerfLoad = 0,
PerfMove = 1,
PerfDebugInfo = 2,
PerfClose = 3,
PerfUnwindingInfo = 4
};
struct BaseEvent {
uint32_t event;
uint32_t size;
uint64_t time_stamp;
};
typedef struct {
struct BaseEvent base;
uint32_t process_id;
uint32_t thread_id;
uint64_t vma;
uint64_t code_address;
uint64_t code_size;
uint64_t code_id;
} CodeLoadEvent;
typedef struct {
struct BaseEvent base;
uint64_t unwind_data_size;
uint64_t eh_frame_hdr_size;
uint64_t mapped_size;
} CodeUnwindingInfoEvent;
static const intptr_t nanoseconds_per_second = 1000000000;
// Dwarf encoding constants
static const uint8_t DwarfUData4 = 0x03;
static const uint8_t DwarfSData4 = 0x0b;
static const uint8_t DwarfPcRel = 0x10;
static const uint8_t DwarfDataRel = 0x30;
// static uint8_t DwarfOmit = 0xff;
typedef struct {
unsigned char version;
unsigned char eh_frame_ptr_enc;
unsigned char fde_count_enc;
unsigned char table_enc;
int32_t eh_frame_ptr;
int32_t eh_fde_count;
int32_t from;
int32_t to;
} EhFrameHeader;
static int64_t get_current_monotonic_ticks(void) {
struct timespec ts;
if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0) {
UNREACHABLE();
return 0;
}
// Convert to nanoseconds.
int64_t result = ts.tv_sec;
result *= nanoseconds_per_second;
result += ts.tv_nsec;
return result;
}
static int64_t get_current_time_microseconds(void) {
// gettimeofday has microsecond resolution.
struct timeval tv;
if (gettimeofday(&tv, NULL) < 0) {
UNREACHABLE();
return 0;
}
return ((int64_t)(tv.tv_sec) * 1000000) + tv.tv_usec;
}
static size_t round_up(int64_t value, int64_t multiple) {
if (multiple == 0) {
// Avoid division by zero
return value;
}
int64_t remainder = value % multiple;
if (remainder == 0) {
// Value is already a multiple of 'multiple'
return value;
}
// Calculate the difference to the next multiple
int64_t difference = multiple - remainder;
// Add the difference to the value
int64_t rounded_up_value = value + difference;
return rounded_up_value;
}
static void perf_map_jit_write_fully(const void* buffer, size_t size) {
FILE* out_file = perf_jit_map_state.perf_map;
const char* ptr = (const char*)(buffer);
while (size > 0) {
const size_t written = fwrite(ptr, 1, size, out_file);
if (written == 0) {
UNREACHABLE();
break;
}
size -= written;
ptr += written;
}
}
static void perf_map_jit_write_header(int pid, FILE* out_file) {
Header header;
header.magic = 0x4A695444;
header.version = 1;
header.size = sizeof(Header);
header.elf_mach_target = GetElfMachineArchitecture();
header.process_id = pid;
header.time_stamp = get_current_time_microseconds();
header.flags = 0;
perf_map_jit_write_fully(&header, sizeof(header));
}
static void* perf_map_jit_init(void) {
char filename[100];
int pid = getpid();
snprintf(filename, sizeof(filename) - 1, "/tmp/jit-%d.dump", pid);
const int fd = open(filename, O_CREAT | O_TRUNC | O_RDWR, 0666);
if (fd == -1) {
return NULL;
}
const long page_size = sysconf(_SC_PAGESIZE); // NOLINT(runtime/int)
if (page_size == -1) {
close(fd);
return NULL;
}
// The perf jit interface forces us to map the first page of the file
// to signal that we are using the interface.
perf_jit_map_state.mapped_buffer = mmap(NULL, page_size, PROT_READ | PROT_EXEC, MAP_PRIVATE, fd, 0);
if (perf_jit_map_state.mapped_buffer == NULL) {
close(fd);
return NULL;
}
perf_jit_map_state.mapped_size = page_size;
perf_jit_map_state.perf_map = fdopen(fd, "w+");
if (perf_jit_map_state.perf_map == NULL) {
close(fd);
return NULL;
}
setvbuf(perf_jit_map_state.perf_map, NULL, _IOFBF, 2 * MB);
perf_map_jit_write_header(pid, perf_jit_map_state.perf_map);
perf_jit_map_state.map_lock = PyThread_allocate_lock();
if (perf_jit_map_state.map_lock == NULL) {
fclose(perf_jit_map_state.perf_map);
return NULL;
}
perf_jit_map_state.code_id = 0;
// trampoline_api.code_padding = PERF_JIT_CODE_PADDING;
return &perf_jit_map_state;
}
/* DWARF definitions. */
#define DWRF_CIE_VERSION 1
enum {
DWRF_CFA_nop = 0x0,
DWRF_CFA_offset_extended = 0x5,
DWRF_CFA_def_cfa = 0xc,
DWRF_CFA_def_cfa_offset = 0xe,
DWRF_CFA_offset_extended_sf = 0x11,
DWRF_CFA_advance_loc = 0x40,
DWRF_CFA_offset = 0x80
};
enum
{
DWRF_EH_PE_absptr = 0x00,
DWRF_EH_PE_omit = 0xff,
/* FDE data encoding. */
DWRF_EH_PE_uleb128 = 0x01,
DWRF_EH_PE_udata2 = 0x02,
DWRF_EH_PE_udata4 = 0x03,
DWRF_EH_PE_udata8 = 0x04,
DWRF_EH_PE_sleb128 = 0x09,
DWRF_EH_PE_sdata2 = 0x0a,
DWRF_EH_PE_sdata4 = 0x0b,
DWRF_EH_PE_sdata8 = 0x0c,
DWRF_EH_PE_signed = 0x08,
/* FDE flags. */
DWRF_EH_PE_pcrel = 0x10,
DWRF_EH_PE_textrel = 0x20,
DWRF_EH_PE_datarel = 0x30,
DWRF_EH_PE_funcrel = 0x40,
DWRF_EH_PE_aligned = 0x50,
DWRF_EH_PE_indirect = 0x80
};
enum { DWRF_TAG_compile_unit = 0x11 };
enum { DWRF_children_no = 0, DWRF_children_yes = 1 };
enum { DWRF_AT_name = 0x03, DWRF_AT_stmt_list = 0x10, DWRF_AT_low_pc = 0x11, DWRF_AT_high_pc = 0x12 };
enum { DWRF_FORM_addr = 0x01, DWRF_FORM_data4 = 0x06, DWRF_FORM_string = 0x08 };
enum { DWRF_LNS_extended_op = 0, DWRF_LNS_copy = 1, DWRF_LNS_advance_pc = 2, DWRF_LNS_advance_line = 3 };
enum { DWRF_LNE_end_sequence = 1, DWRF_LNE_set_address = 2 };
enum {
#ifdef __x86_64__
/* Yes, the order is strange, but correct. */
DWRF_REG_AX,
DWRF_REG_DX,
DWRF_REG_CX,
DWRF_REG_BX,
DWRF_REG_SI,
DWRF_REG_DI,
DWRF_REG_BP,
DWRF_REG_SP,
DWRF_REG_8,
DWRF_REG_9,
DWRF_REG_10,
DWRF_REG_11,
DWRF_REG_12,
DWRF_REG_13,
DWRF_REG_14,
DWRF_REG_15,
DWRF_REG_RA,
#elif defined(__aarch64__) && defined(__AARCH64EL__) && !defined(__ILP32__)
DWRF_REG_SP = 31,
DWRF_REG_RA = 30,
#else
# error "Unsupported target architecture"
#endif
};
typedef struct ELFObjectContext
{
uint8_t* p; /* Pointer to next address in obj.space. */
uint8_t* startp; /* Pointer to start address in obj.space. */
uint8_t* eh_frame_p; /* Pointer to start address in obj.space. */
uint32_t code_size; /* Size of machine code. */
} ELFObjectContext;
/* Append a null-terminated string. */
static uint32_t
elfctx_append_string(ELFObjectContext* ctx, const char* str)
{
uint8_t* p = ctx->p;
uint32_t ofs = (uint32_t)(p - ctx->startp);
do {
*p++ = (uint8_t)*str;
} while (*str++);
ctx->p = p;
return ofs;
}
/* Append a SLEB128 value. */
static void
elfctx_append_sleb128(ELFObjectContext* ctx, int32_t v)
{
uint8_t* p = ctx->p;
for (; (uint32_t)(v + 0x40) >= 0x80; v >>= 7) {
*p++ = (uint8_t)((v & 0x7f) | 0x80);
}
*p++ = (uint8_t)(v & 0x7f);
ctx->p = p;
}
/* Append a ULEB128 to buffer. */
static void
elfctx_append_uleb128(ELFObjectContext* ctx, uint32_t v)
{
uint8_t* p = ctx->p;
for (; v >= 0x80; v >>= 7) {
*p++ = (char)((v & 0x7f) | 0x80);
}
*p++ = (char)v;
ctx->p = p;
}
/* Shortcuts to generate DWARF structures. */
#define DWRF_U8(x) (*p++ = (x))
#define DWRF_I8(x) (*(int8_t*)p = (x), p++)
#define DWRF_U16(x) (*(uint16_t*)p = (x), p += 2)
#define DWRF_U32(x) (*(uint32_t*)p = (x), p += 4)
#define DWRF_ADDR(x) (*(uintptr_t*)p = (x), p += sizeof(uintptr_t))
#define DWRF_UV(x) (ctx->p = p, elfctx_append_uleb128(ctx, (x)), p = ctx->p)
#define DWRF_SV(x) (ctx->p = p, elfctx_append_sleb128(ctx, (x)), p = ctx->p)
#define DWRF_STR(str) (ctx->p = p, elfctx_append_string(ctx, (str)), p = ctx->p)
#define DWRF_ALIGNNOP(s) \
while ((uintptr_t)p & ((s)-1)) { \
*p++ = DWRF_CFA_nop; \
}
#define DWRF_SECTION(name, stmt) \
{ \
uint32_t* szp_##name = (uint32_t*)p; \
p += 4; \
stmt; \
*szp_##name = (uint32_t)((p - (uint8_t*)szp_##name) - 4); \
}
/* Initialize .eh_frame section. */
static void
elf_init_ehframe(ELFObjectContext* ctx)
{
uint8_t* p = ctx->p;
uint8_t* framep = p;
/* Emit DWARF EH CIE. */
DWRF_SECTION(CIE, DWRF_U32(0); /* Offset to CIE itself. */
DWRF_U8(DWRF_CIE_VERSION);
DWRF_STR("zR"); /* Augmentation. */
DWRF_UV(1); /* Code alignment factor. */
DWRF_SV(-(int64_t)sizeof(uintptr_t)); /* Data alignment factor. */
DWRF_U8(DWRF_REG_RA); /* Return address register. */
DWRF_UV(1);
DWRF_U8(DWRF_EH_PE_pcrel | DWRF_EH_PE_sdata4); /* Augmentation data. */
DWRF_U8(DWRF_CFA_def_cfa); DWRF_UV(DWRF_REG_SP); DWRF_UV(sizeof(uintptr_t));
DWRF_U8(DWRF_CFA_offset|DWRF_REG_RA); DWRF_UV(1);
DWRF_ALIGNNOP(sizeof(uintptr_t));
)
ctx->eh_frame_p = p;
/* Emit DWARF EH FDE. */
DWRF_SECTION(FDE, DWRF_U32((uint32_t)(p - framep)); /* Offset to CIE. */
DWRF_U32(-0x30); /* Machine code offset relative to .text. */
DWRF_U32(ctx->code_size); /* Machine code length. */
DWRF_U8(0); /* Augmentation data. */
/* Registers saved in CFRAME. */
#ifdef __x86_64__
DWRF_U8(DWRF_CFA_advance_loc | 4);
DWRF_U8(DWRF_CFA_def_cfa_offset); DWRF_UV(16);
DWRF_U8(DWRF_CFA_advance_loc | 6);
DWRF_U8(DWRF_CFA_def_cfa_offset); DWRF_UV(8);
/* Extra registers saved for JIT-compiled code. */
#elif defined(__aarch64__) && defined(__AARCH64EL__) && !defined(__ILP32__)
DWRF_U8(DWRF_CFA_advance_loc | 1);
DWRF_U8(DWRF_CFA_def_cfa_offset); DWRF_UV(16);
DWRF_U8(DWRF_CFA_offset | 29); DWRF_UV(2);
DWRF_U8(DWRF_CFA_offset | 30); DWRF_UV(1);
DWRF_U8(DWRF_CFA_advance_loc | 3);
DWRF_U8(DWRF_CFA_offset | -(64 - 29));
DWRF_U8(DWRF_CFA_offset | -(64 - 30));
DWRF_U8(DWRF_CFA_def_cfa_offset);
DWRF_UV(0);
#else
# error "Unsupported target architecture"
#endif
DWRF_ALIGNNOP(sizeof(uintptr_t));)
ctx->p = p;
}
static void perf_map_jit_write_entry(void *state, const void *code_addr,
unsigned int code_size, PyCodeObject *co)
{
if (perf_jit_map_state.perf_map == NULL) {
void* ret = perf_map_jit_init();
if(ret == NULL){
return;
}
}
const char *entry = "";
if (co->co_qualname != NULL) {
entry = PyUnicode_AsUTF8(co->co_qualname);
}
const char *filename = "";
if (co->co_filename != NULL) {
filename = PyUnicode_AsUTF8(co->co_filename);
}
size_t perf_map_entry_size = snprintf(NULL, 0, "py::%s:%s", entry, filename) + 1;
char* perf_map_entry = (char*) PyMem_RawMalloc(perf_map_entry_size);
if (perf_map_entry == NULL) {
return;
}
snprintf(perf_map_entry, perf_map_entry_size, "py::%s:%s", entry, filename);
const size_t name_length = strlen(perf_map_entry);
uword base = (uword)code_addr;
uword size = code_size;
// Write the code unwinding info event.
// Create unwinding information (eh frame)
ELFObjectContext ctx;
char buffer[1024];
ctx.code_size = code_size;
ctx.startp = ctx.p = (uint8_t*)buffer;
elf_init_ehframe(&ctx);
int eh_frame_size = ctx.p - ctx.startp;
// Populate the unwind info event for perf
CodeUnwindingInfoEvent ev2;
ev2.base.event = PerfUnwindingInfo;
ev2.base.time_stamp = get_current_monotonic_ticks();
ev2.unwind_data_size = sizeof(EhFrameHeader) + eh_frame_size;
// Ensure we have enough space between DSOs when perf maps them
assert(ev2.unwind_data_size <= PERF_JIT_CODE_PADDING);
ev2.eh_frame_hdr_size = sizeof(EhFrameHeader);
ev2.mapped_size = round_up(ev2.unwind_data_size, 16);
int content_size = sizeof(ev2) + sizeof(EhFrameHeader) + eh_frame_size;
int padding_size = round_up(content_size, 8) - content_size;
ev2.base.size = content_size + padding_size;
perf_map_jit_write_fully(&ev2, sizeof(ev2));
// Populate the eh Frame header
EhFrameHeader f;
f.version = 1;
f.eh_frame_ptr_enc = DwarfSData4 | DwarfPcRel;
f.fde_count_enc = DwarfUData4;
f.table_enc = DwarfSData4 | DwarfDataRel;
f.eh_frame_ptr = -(eh_frame_size + 4 * sizeof(unsigned char));
f.eh_fde_count = 1;
f.from = -(round_up(code_size, 8) + eh_frame_size);
int cie_size = ctx.eh_frame_p - ctx.startp;
f.to = -(eh_frame_size - cie_size);
perf_map_jit_write_fully(ctx.startp, eh_frame_size);
perf_map_jit_write_fully(&f, sizeof(f));
char padding_bytes[] = "\0\0\0\0\0\0\0\0";
perf_map_jit_write_fully(&padding_bytes, padding_size);
// Write the code load event.
CodeLoadEvent ev;
ev.base.event = PerfLoad;
ev.base.size = sizeof(ev) + (name_length+1) + size;
ev.base.time_stamp = get_current_monotonic_ticks();
ev.process_id = getpid();
ev.thread_id = gettid();
ev.vma = base;
ev.code_address = base;
ev.code_size = size;
perf_jit_map_state.code_id += 1;
ev.code_id = perf_jit_map_state.code_id;
perf_map_jit_write_fully(&ev, sizeof(ev));
perf_map_jit_write_fully(perf_map_entry, name_length+1);
perf_map_jit_write_fully((void*)(base), size);
return;
}
static int perf_map_jit_fini(void* state) {
if (perf_jit_map_state.perf_map != NULL) {
// close the file
PyThread_acquire_lock(perf_jit_map_state.map_lock, 1);
fclose(perf_jit_map_state.perf_map);
PyThread_release_lock(perf_jit_map_state.map_lock);
// clean up the lock and state
PyThread_free_lock(perf_jit_map_state.map_lock);
perf_jit_map_state.perf_map = NULL;
}
if (perf_jit_map_state.mapped_buffer != NULL) {
munmap(perf_jit_map_state.mapped_buffer, perf_jit_map_state.mapped_size);
}
trampoline_api.state = NULL;
return 0;
}
_PyPerf_Callbacks _Py_perfmap_jit_callbacks = {
&perf_map_jit_init,
&perf_map_jit_write_entry,
&perf_map_jit_fini,
};
#endif

52
Python/perf_trampoline.c
View File

@ -143,6 +143,8 @@ any DWARF information available for them).
#include <sys/mman.h> // mmap()
#include <sys/types.h>
#include <unistd.h> // sysconf()
#include <sys/time.h> // gettimeofday()
#if defined(__arm__) || defined(__arm64__) || defined(__aarch64__)
#define PY_HAVE_INVALIDATE_ICACHE
@ -187,12 +189,19 @@ struct code_arena_st {
typedef struct code_arena_st code_arena_t;
typedef struct trampoline_api_st trampoline_api_t;
enum perf_trampoline_type {
PERF_TRAMPOLINE_UNSET = 0,
PERF_TRAMPOLINE_TYPE_MAP = 1,
PERF_TRAMPOLINE_TYPE_JITDUMP = 2,
};
#define perf_status _PyRuntime.ceval.perf.status
#define extra_code_index _PyRuntime.ceval.perf.extra_code_index
#define perf_code_arena _PyRuntime.ceval.perf.code_arena
#define trampoline_api _PyRuntime.ceval.perf.trampoline_api
#define perf_map_file _PyRuntime.ceval.perf.map_file
#define persist_after_fork _PyRuntime.ceval.perf.persist_after_fork
#define perf_trampoline_type _PyRuntime.ceval.perf.perf_trampoline_type
static void
perf_map_write_entry(void *state, const void *code_addr,
@ -220,6 +229,8 @@ static void*
perf_map_init_state(void)
{
PyUnstable_PerfMapState_Init();
trampoline_api.code_padding = 0;
perf_trampoline_type = PERF_TRAMPOLINE_TYPE_MAP;
return NULL;
}
@ -236,6 +247,30 @@ _PyPerf_Callbacks _Py_perfmap_callbacks = {
&perf_map_free_state,
};
static size_t round_up(int64_t value, int64_t multiple) {
if (multiple == 0) {
// Avoid division by zero
return value;
}
int64_t remainder = value % multiple;
if (remainder == 0) {
// Value is already a multiple of 'multiple'
return value;
}
// Calculate the difference to the next multiple
int64_t difference = multiple - remainder;
// Add the difference to the value
int64_t rounded_up_value = value + difference;
return rounded_up_value;
}
// TRAMPOLINE MANAGEMENT API
static int
new_code_arena(void)
{
@ -256,6 +291,7 @@ new_code_arena(void)
void *start = &_Py_trampoline_func_start;
void *end = &_Py_trampoline_func_end;
size_t code_size = end - start;
size_t chunk_size = round_up(code_size + trampoline_api.code_padding, 16);
// TODO: Check the effect of alignment of the code chunks. Initial investigation
// showed that this has no effect on performance in x86-64 or aarch64 and the current
// version has the advantage that the unwinder in GDB can unwind across JIT-ed code.
@ -264,9 +300,9 @@ new_code_arena(void)
// measurable performance improvement by rounding trampolines up to 32-bit
// or 64-bit alignment.
size_t n_copies = mem_size / code_size;
size_t n_copies = mem_size / chunk_size;
for (size_t i = 0; i < n_copies; i++) {
memcpy(memory + i * code_size, start, code_size * sizeof(char));
memcpy(memory + i * chunk_size, start, code_size * sizeof(char));
}
// Some systems may prevent us from creating executable code on the fly.
int res = mprotect(memory, mem_size, PROT_READ | PROT_EXEC);
@ -320,16 +356,18 @@ static inline py_trampoline
code_arena_new_code(code_arena_t *code_arena)
{
py_trampoline trampoline = (py_trampoline)code_arena->current_addr;
code_arena->size_left -= code_arena->code_size;
code_arena->current_addr += code_arena->code_size;
size_t total_code_size = round_up(code_arena->code_size + trampoline_api.code_padding, 16);
code_arena->size_left -= total_code_size;
code_arena->current_addr += total_code_size;
return trampoline;
}
static inline py_trampoline
compile_trampoline(void)
{
size_t total_code_size = round_up(perf_code_arena->code_size + trampoline_api.code_padding, 16);
if ((perf_code_arena == NULL) ||
(perf_code_arena->size_left <= perf_code_arena->code_size)) {
(perf_code_arena->size_left <= total_code_size)) {
if (new_code_arena() < 0) {
return NULL;
}
@ -480,6 +518,7 @@ _PyPerfTrampoline_Fini(void)
}
if (perf_status == PERF_STATUS_OK) {
trampoline_api.free_state(trampoline_api.state);
perf_trampoline_type = PERF_TRAMPOLINE_UNSET;
}
extra_code_index = -1;
perf_status = PERF_STATUS_NO_INIT;
@ -508,6 +547,9 @@ _PyPerfTrampoline_AfterFork_Child(void)
{
#ifdef PY_HAVE_PERF_TRAMPOLINE
if (persist_after_fork) {
if (perf_trampoline_type != PERF_TRAMPOLINE_TYPE_MAP) {
return PyStatus_Error("Failed to copy perf map file as perf trampoline type is not type map.");
}
_PyPerfTrampoline_Fini();
char filename[256];
pid_t parent_pid = getppid();

9
Python/pylifecycle.c
View File

@ -1210,7 +1210,14 @@ init_interp_main(PyThreadState *tstate)
#ifdef PY_HAVE_PERF_TRAMPOLINE
if (config->perf_profiling) {
if (_PyPerfTrampoline_SetCallbacks(&_Py_perfmap_callbacks) < 0 ||
_PyPerf_Callbacks *cur_cb;
if (config->perf_profiling == 1) {
cur_cb = &_Py_perfmap_callbacks;
}
else {
cur_cb = &_Py_perfmap_jit_callbacks;
}
if (_PyPerfTrampoline_SetCallbacks(cur_cb) < 0 ||
_PyPerfTrampoline_Init(config->perf_profiling) < 0) {
return _PyStatus_ERR("can't initialize the perf trampoline");
}

10
Python/sysmodule.c
View File

@ -2282,6 +2282,16 @@ sys_activate_stack_trampoline_impl(PyObject *module, const char *backend)
return NULL;
}
}
else if (strcmp(backend, "perfjit") == 0) {
_PyPerf_Callbacks cur_cb;
_PyPerfTrampoline_GetCallbacks(&cur_cb);
if (cur_cb.write_state != _Py_perfmap_jit_callbacks.write_state) {
if (_PyPerfTrampoline_SetCallbacks(&_Py_perfmap_jit_callbacks) < 0 ) {
PyErr_SetString(PyExc_ValueError, "can't activate perf jit trampoline");
return NULL;
}
}
}
}
else {
PyErr_Format(PyExc_ValueError, "invalid backend: %s", backend);

2
Tools/c-analyzer/cpython/ignored.tsv
View File

@ -365,6 +365,8 @@ Python/intrinsics.c - _PyIntrinsics_BinaryFunctions -
Python/lock.c - TIME_TO_BE_FAIR_NS -
Python/opcode_targets.h - opcode_targets -
Python/perf_trampoline.c - _Py_perfmap_callbacks -
Python/perf_jit_trampoline.c - _Py_perfmap_jit_callbacks -
Python/perf_jit_trampoline.c - perf_jit_map_state -
Python/pyhash.c - PyHash_Func -
Python/pylifecycle.c - _C_LOCALE_WARNING -
Python/pylifecycle.c - _PyOS_mystrnicmp_hack -

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