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all tasks profiler
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@d-netto
d-netto committed Sep 26, 2024
1 parent 7a76e32 commit 6b80fe3
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Showing 8 changed files with 410 additions and 206 deletions.
17 changes: 17 additions & 0 deletions src/julia_internal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -211,6 +211,23 @@ JL_DLLEXPORT void jl_unlock_profile_wr(void) JL_NOTSAFEPOINT JL_NOTSAFEPOINT_LEA
int jl_lock_stackwalk(void) JL_NOTSAFEPOINT JL_NOTSAFEPOINT_ENTER;
void jl_unlock_stackwalk(int lockret) JL_NOTSAFEPOINT JL_NOTSAFEPOINT_LEAVE;

arraylist_t jl_get_all_tasks_arraylist(void) JL_NOTSAFEPOINT;
typedef struct {
size_t bt_size;
int tid;
} jl_record_backtrace_result_t;
JL_DLLEXPORT jl_record_backtrace_result_t jl_record_backtrace(jl_task_t *t, struct _jl_bt_element_t *bt_data,
size_t max_bt_size) JL_NOTSAFEPOINT;
extern volatile struct _jl_bt_element_t *profile_bt_data_prof;
extern volatile size_t profile_bt_size_max;
extern volatile size_t profile_bt_size_cur;
extern volatile int profile_running;
extern volatile int profile_all_tasks;
STATIC_INLINE int all_tasks_profile_running(void)
{
return profile_running && profile_all_tasks;
}

// number of cycles since power-on
static inline uint64_t cycleclock(void) JL_NOTSAFEPOINT
{
Expand Down
38 changes: 19 additions & 19 deletions src/signal-handling.c
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Original file line number Diff line number Diff line change
Expand Up @@ -18,46 +18,46 @@ extern "C" {
#include <threading.h>

// Profiler control variables
// Note: these "static" variables are also used in "signals-*.c"
static volatile jl_bt_element_t *bt_data_prof = NULL;
static volatile size_t bt_size_max = 0;
static volatile size_t bt_size_cur = 0;
volatile jl_bt_element_t *profile_bt_data_prof = NULL;
volatile size_t profile_bt_size_max = 0;
volatile size_t profile_bt_size_cur = 0;
static volatile uint64_t nsecprof = 0;
static volatile int running = 0;
static const uint64_t GIGA = 1000000000ULL;
volatile int profile_running = 0;
volatile int profile_all_tasks = 0;
static const uint64_t GIGA = 1000000000ULL;
// Timers to take samples at intervals
JL_DLLEXPORT void jl_profile_stop_timer(void);
JL_DLLEXPORT int jl_profile_start_timer(void);
JL_DLLEXPORT int jl_profile_start_timer(uint8_t);

///////////////////////
// Utility functions //
///////////////////////
JL_DLLEXPORT int jl_profile_init(size_t maxsize, uint64_t delay_nsec)
{
bt_size_max = maxsize;
profile_bt_size_max = maxsize;
nsecprof = delay_nsec;
if (bt_data_prof != NULL)
free((void*)bt_data_prof);
bt_data_prof = (jl_bt_element_t*) calloc(maxsize, sizeof(jl_bt_element_t));
if (bt_data_prof == NULL && maxsize > 0)
if (profile_bt_data_prof != NULL)
free((void*)profile_bt_data_prof);
profile_bt_data_prof = (jl_bt_element_t*) calloc(maxsize, sizeof(jl_bt_element_t));
if (profile_bt_data_prof == NULL && maxsize > 0)
return -1;
bt_size_cur = 0;
profile_bt_size_cur = 0;
return 0;
}

JL_DLLEXPORT uint8_t *jl_profile_get_data(void)
{
return (uint8_t*) bt_data_prof;
return (uint8_t*) profile_bt_data_prof;
}

JL_DLLEXPORT size_t jl_profile_len_data(void)
{
return bt_size_cur;
return profile_bt_size_cur;
}

JL_DLLEXPORT size_t jl_profile_maxlen_data(void)
{
return bt_size_max;
return profile_bt_size_max;
}

JL_DLLEXPORT uint64_t jl_profile_delay_nsec(void)
Expand All @@ -67,12 +67,12 @@ JL_DLLEXPORT uint64_t jl_profile_delay_nsec(void)

JL_DLLEXPORT void jl_profile_clear_data(void)
{
bt_size_cur = 0;
profile_bt_size_cur = 0;
}

JL_DLLEXPORT int jl_profile_is_running(void)
{
return running;
return profile_running;
}

// Any function that acquires this lock must be either a unmanaged thread
Expand Down Expand Up @@ -184,7 +184,7 @@ JL_DLLEXPORT int jl_profile_is_buffer_full(void)
// Declare buffer full if there isn't enough room to sample even just the
// thread metadata and one max-sized frame. The `+ 6` is for the two block
// terminator `0`'s plus the 4 metadata entries.
return bt_size_cur + ((JL_BT_MAX_ENTRY_SIZE + 1) + 6) > bt_size_max;
return profile_bt_size_cur + ((JL_BT_MAX_ENTRY_SIZE + 1) + 6) > profile_bt_size_max;
}

static uint64_t jl_last_sigint_trigger = 0;
Expand Down
177 changes: 96 additions & 81 deletions src/signals-mach.c
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Original file line number Diff line number Diff line change
Expand Up @@ -724,6 +724,85 @@ void jl_unlock_stackwalk(int lockret)
jl_unlock_profile_mach(1, lockret);
}

// assumes holding `jl_lock_profile_mach`
void jl_profile_thread_mach(int tid)
{
// if there is no space left, return early
if (jl_profile_is_buffer_full()) {
jl_profile_stop_timer();
return;
}
if (_dyld_dlopen_atfork_prepare != NULL && _dyld_dlopen_atfork_parent != NULL)
_dyld_dlopen_atfork_prepare();
if (_dyld_atfork_prepare != NULL && _dyld_atfork_parent != NULL)
_dyld_atfork_prepare(); // briefly acquire the dlsym lock
host_thread_state_t state;
int valid_thread = jl_thread_suspend_and_get_state2(tid, &state);
unw_context_t *uc = (unw_context_t*)&state;
if (_dyld_atfork_prepare != NULL && _dyld_atfork_parent != NULL)
_dyld_atfork_parent(); // quickly release the dlsym lock
if (_dyld_dlopen_atfork_prepare != NULL && _dyld_dlopen_atfork_parent != NULL)
_dyld_dlopen_atfork_parent();
if (!valid_thread)
return;
if (profile_running) {
#ifdef LLVMLIBUNWIND
/*
* Unfortunately compact unwind info is incorrectly generated for quite a number of
* libraries by quite a large number of compilers. We can fall back to DWARF unwind info
* in some cases, but in quite a number of cases (especially libraries not compiled in debug
* mode, only the compact unwind info may be available). Even more unfortunately, there is no
* way to detect such bogus compact unwind info (other than noticing the resulting segfault).
* What we do here is ugly, but necessary until the compact unwind info situation improves.
* We try to use the compact unwind info and if that results in a segfault, we retry with DWARF info.
* Note that in a small number of cases this may result in bogus stack traces, but at least the topmost
* entry will always be correct, and the number of cases in which this is an issue is rather small.
* Other than that, this implementation is not incorrect as the other thread is paused while we are profiling
* and during stack unwinding we only ever read memory, but never write it.
*/

forceDwarf = 0;
unw_getcontext(&profiler_uc); // will resume from this point if the next lines segfault at any point

if (forceDwarf == 0) {
// Save the backtrace
profile_bt_size_cur += rec_backtrace_ctx((jl_bt_element_t*)profile_bt_data_prof + profile_bt_size_cur, profile_bt_size_max - profile_bt_size_cur - 1, uc, NULL);
}
else if (forceDwarf == 1) {
profile_bt_size_cur += rec_backtrace_ctx_dwarf((jl_bt_element_t*)profile_bt_data_prof + profile_bt_size_cur, profile_bt_size_max - profile_bt_size_cur - 1, uc, NULL);
}
else if (forceDwarf == -1) {
jl_safe_printf("WARNING: profiler attempt to access an invalid memory location\n");
}

forceDwarf = -2;
#else
profile_bt_size_cur += rec_backtrace_ctx((jl_bt_element_t*)profile_bt_data_prof + profile_bt_size_cur, profile_bt_size_max - profile_bt_size_cur - 1, uc, NULL);
#endif
jl_ptls_t ptls = jl_atomic_load_relaxed(&jl_all_tls_states)[tid];

// store threadid but add 1 as 0 is preserved to indicate end of block
profile_bt_data_prof[profile_bt_size_cur++].uintptr = ptls->tid + 1;

// store task id (never null)
profile_bt_data_prof[profile_bt_size_cur++].jlvalue = (jl_value_t*)jl_atomic_load_relaxed(&ptls->current_task);

// store cpu cycle clock
profile_bt_data_prof[profile_bt_size_cur++].uintptr = cycleclock();

// store whether thread is sleeping but add 1 as 0 is preserved to indicate end of block
profile_bt_data_prof[profile_bt_size_cur++].uintptr = jl_atomic_load_relaxed(&ptls->sleep_check_state) + 1;

// Mark the end of this block with two 0's
profile_bt_data_prof[profile_bt_size_cur++].uintptr = 0;
profile_bt_data_prof[profile_bt_size_cur++].uintptr = 0;
}
// We're done! Resume the thread.
jl_thread_resume(tid);
}

void jl_profile_task_unix(void);

void *mach_profile_listener(void *arg)
{
(void)arg;
Expand All @@ -741,88 +820,21 @@ void *mach_profile_listener(void *arg)
// sample each thread, round-robin style in reverse order
// (so that thread zero gets notified last)
int keymgr_locked = jl_lock_profile_mach(0);

int nthreads = jl_atomic_load_acquire(&jl_n_threads);
int *randperm = profile_get_randperm(nthreads);
for (int idx = nthreads; idx-- > 0; ) {
// Stop the threads in the random or reverse round-robin order.
int i = randperm[idx];
// if there is no space left, break early
if (jl_profile_is_buffer_full()) {
jl_profile_stop_timer();
break;
}

if (_dyld_dlopen_atfork_prepare != NULL && _dyld_dlopen_atfork_parent != NULL)
_dyld_dlopen_atfork_prepare();
if (_dyld_atfork_prepare != NULL && _dyld_atfork_parent != NULL)
_dyld_atfork_prepare(); // briefly acquire the dlsym lock
host_thread_state_t state;
int valid_thread = jl_thread_suspend_and_get_state2(i, &state);
unw_context_t *uc = (unw_context_t*)&state;
if (_dyld_atfork_prepare != NULL && _dyld_atfork_parent != NULL)
_dyld_atfork_parent(); // quickly release the dlsym lock
if (_dyld_dlopen_atfork_prepare != NULL && _dyld_dlopen_atfork_parent != NULL)
_dyld_dlopen_atfork_parent();
if (!valid_thread)
continue;
if (running) {
#ifdef LLVMLIBUNWIND
/*
* Unfortunately compact unwind info is incorrectly generated for quite a number of
* libraries by quite a large number of compilers. We can fall back to DWARF unwind info
* in some cases, but in quite a number of cases (especially libraries not compiled in debug
* mode, only the compact unwind info may be available). Even more unfortunately, there is no
* way to detect such bogus compact unwind info (other than noticing the resulting segfault).
* What we do here is ugly, but necessary until the compact unwind info situation improves.
* We try to use the compact unwind info and if that results in a segfault, we retry with DWARF info.
* Note that in a small number of cases this may result in bogus stack traces, but at least the topmost
* entry will always be correct, and the number of cases in which this is an issue is rather small.
* Other than that, this implementation is not incorrect as the other thread is paused while we are profiling
* and during stack unwinding we only ever read memory, but never write it.
*/

forceDwarf = 0;
unw_getcontext(&profiler_uc); // will resume from this point if the next lines segfault at any point

if (forceDwarf == 0) {
// Save the backtrace
bt_size_cur += rec_backtrace_ctx((jl_bt_element_t*)bt_data_prof + bt_size_cur, bt_size_max - bt_size_cur - 1, uc, NULL);
}
else if (forceDwarf == 1) {
bt_size_cur += rec_backtrace_ctx_dwarf((jl_bt_element_t*)bt_data_prof + bt_size_cur, bt_size_max - bt_size_cur - 1, uc, NULL);
}
else if (forceDwarf == -1) {
jl_safe_printf("WARNING: profiler attempt to access an invalid memory location\n");
}

forceDwarf = -2;
#else
bt_size_cur += rec_backtrace_ctx((jl_bt_element_t*)bt_data_prof + bt_size_cur, bt_size_max - bt_size_cur - 1, uc, NULL);
#endif
jl_ptls_t ptls = jl_atomic_load_relaxed(&jl_all_tls_states)[i];

// META_OFFSET_THREADID store threadid but add 1 as 0 is preserved to indicate end of block
bt_data_prof[bt_size_cur++].uintptr = ptls->tid + 1;

// META_OFFSET_TASKID store task id (never null)
bt_data_prof[bt_size_cur++].jlvalue = (jl_value_t*)jl_atomic_load_relaxed(&ptls->current_task);

// META_OFFSET_CPUCYCLECLOCK store cpu cycle clock
bt_data_prof[bt_size_cur++].uintptr = cycleclock();

// META_OFFSET_SLEEPSTATE store whether thread is sleeping but add 1 as 0 is preserved to indicate end of block
bt_data_prof[bt_size_cur++].uintptr = jl_atomic_load_relaxed(&ptls->sleep_check_state) + 1;

// Mark the end of this block with two 0's
bt_data_prof[bt_size_cur++].uintptr = 0;
bt_data_prof[bt_size_cur++].uintptr = 0;
if (profile_all_tasks) {
// Don't take the stackwalk lock here since it's already taken in `jl_rec_backtrace`
jl_profile_task_unix();
}
else {
int *randperm = profile_get_randperm(nthreads);
for (int idx = nthreads; idx-- > 0; ) {
// Stop the threads in random order.
int i = randperm[idx];
jl_profile_thread_mach(i);
}
// We're done! Resume the thread.
jl_thread_resume(i);
}
jl_unlock_profile_mach(0, keymgr_locked);
if (running) {
if (profile_running) {
jl_check_profile_autostop();
// Reset the alarm
kern_return_t ret = clock_alarm(clk, TIME_RELATIVE, timerprof, profile_port);
Expand All @@ -831,7 +843,8 @@ void *mach_profile_listener(void *arg)
}
}

JL_DLLEXPORT int jl_profile_start_timer(void)

JL_DLLEXPORT int jl_profile_start_timer(uint8_t all_tasks)
{
kern_return_t ret;
if (!profile_started) {
Expand Down Expand Up @@ -860,7 +873,8 @@ JL_DLLEXPORT int jl_profile_start_timer(void)
timerprof.tv_sec = nsecprof/GIGA;
timerprof.tv_nsec = nsecprof%GIGA;

running = 1;
profile_running = 1;
profile_all_tasks = all_tasks;
// ensure the alarm is running
ret = clock_alarm(clk, TIME_RELATIVE, timerprof, profile_port);
HANDLE_MACH_ERROR("clock_alarm", ret);
Expand All @@ -870,5 +884,6 @@ JL_DLLEXPORT int jl_profile_start_timer(void)

JL_DLLEXPORT void jl_profile_stop_timer(void)
{
running = 0;
profile_running = 0;
profile_all_tasks = 0;
}
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