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GH-116968: Remove branch from advance_backoff_counter (GH-124469)

This commit is contained in:
Mark Shannon 2024-10-07 11:46:33 +01:00 committed by GitHub
parent 31516c98dd
commit f55273b3b7
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GPG Key ID: B5690EEEBB952194
4 changed files with 29 additions and 33 deletions
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46
Include/internal/pycore_backoff.h
View File

@ -15,13 +15,7 @@ extern "C" {
typedef struct {
union {
struct {
uint16_t backoff : 4;
uint16_t value : 12;
};
uint16_t as_counter; // For printf("%#x", ...)
};
uint16_t value_and_backoff;
} _Py_BackoffCounter;
@ -38,17 +32,19 @@ typedef struct {
and a 4-bit 'backoff' field. When resetting the counter, the
backoff field is incremented (until it reaches a limit) and the
value is set to a bit mask representing the value 2**backoff - 1.
The maximum backoff is 12 (the number of value bits).
The maximum backoff is 12 (the number of bits in the value).
There is an exceptional value which must not be updated, 0xFFFF.
*/
#define UNREACHABLE_BACKOFF 0xFFFF
#define BACKOFF_BITS 4
#define MAX_BACKOFF 12
#define UNREACHABLE_BACKOFF 15
static inline bool
is_unreachable_backoff_counter(_Py_BackoffCounter counter)
{
return counter.as_counter == UNREACHABLE_BACKOFF;
return counter.value_and_backoff == UNREACHABLE_BACKOFF;
}
static inline _Py_BackoffCounter
@ -57,8 +53,7 @@ make_backoff_counter(uint16_t value, uint16_t backoff)
assert(backoff <= 15);
assert(value <= 0xFFF);
_Py_BackoffCounter result;
result.value = value;
result.backoff = backoff;
result.value_and_backoff = (value << BACKOFF_BITS) | backoff;
return result;
}
@ -66,7 +61,7 @@ static inline _Py_BackoffCounter
forge_backoff_counter(uint16_t counter)
{
_Py_BackoffCounter result;
result.as_counter = counter;
result.value_and_backoff = counter;
return result;
}
@ -74,35 +69,36 @@ static inline _Py_BackoffCounter
restart_backoff_counter(_Py_BackoffCounter counter)
{
assert(!is_unreachable_backoff_counter(counter));
if (counter.backoff < 12) {
return make_backoff_counter((1 << (counter.backoff + 1)) - 1, counter.backoff + 1);
int backoff = counter.value_and_backoff & 15;
if (backoff < MAX_BACKOFF) {
return make_backoff_counter((1 << (backoff + 1)) - 1, backoff + 1);
}
else {
return make_backoff_counter((1 << 12) - 1, 12);
return make_backoff_counter((1 << MAX_BACKOFF) - 1, MAX_BACKOFF);
}
}
static inline _Py_BackoffCounter
pause_backoff_counter(_Py_BackoffCounter counter)
{
return make_backoff_counter(counter.value | 1, counter.backoff);
_Py_BackoffCounter result;
result.value_and_backoff = counter.value_and_backoff | (1 << BACKOFF_BITS);
return result;
}
static inline _Py_BackoffCounter
advance_backoff_counter(_Py_BackoffCounter counter)
{
if (!is_unreachable_backoff_counter(counter)) {
return make_backoff_counter((counter.value - 1) & 0xFFF, counter.backoff);
}
else {
return counter;
}
_Py_BackoffCounter result;
result.value_and_backoff = counter.value_and_backoff - (1 << BACKOFF_BITS);
return result;
}
static inline bool
backoff_counter_triggers(_Py_BackoffCounter counter)
{
return counter.value == 0;
/* Test whether the value is zero and the backoff is not UNREACHABLE_BACKOFF */
return counter.value_and_backoff < UNREACHABLE_BACKOFF;
}
/* Initial JUMP_BACKWARD counter.
@ -136,7 +132,7 @@ initial_temperature_backoff_counter(void)
static inline _Py_BackoffCounter
initial_unreachable_backoff_counter(void)
{
return forge_backoff_counter(UNREACHABLE_BACKOFF);
return make_backoff_counter(0, UNREACHABLE_BACKOFF);
}
#ifdef __cplusplus

4
Python/bytecodes.c
View File

@ -4705,7 +4705,7 @@ dummy_func(
printf("SIDE EXIT: [UOp ");
_PyUOpPrint(&next_uop[-1]);
printf(", exit %u, temp %d, target %d -> %s]\n",
exit - current_executor->exits, exit->temperature.as_counter,
exit - current_executor->exits, exit->temperature.value_and_backoff,
(int)(target - _PyCode_CODE(code)),
_PyOpcode_OpName[target->op.code]);
}
@ -4794,7 +4794,7 @@ dummy_func(
printf("DYNAMIC EXIT: [UOp ");
_PyUOpPrint(&next_uop[-1]);
printf(", exit %u, temp %d, target %d -> %s]\n",
exit - current_executor->exits, exit->temperature.as_counter,
exit - current_executor->exits, exit->temperature.value_and_backoff,
(int)(target - _PyCode_CODE(_PyFrame_GetCode(frame))),
_PyOpcode_OpName[target->op.code]);
}

4
Python/executor_cases.c.h generated
View File

@ -5252,7 +5252,7 @@
printf("SIDE EXIT: [UOp ");
_PyUOpPrint(&next_uop[-1]);
printf(", exit %u, temp %d, target %d -> %s]\n",
exit - current_executor->exits, exit->temperature.as_counter,
exit - current_executor->exits, exit->temperature.value_and_backoff,
(int)(target - _PyCode_CODE(code)),
_PyOpcode_OpName[target->op.code]);
}
@ -5390,7 +5390,7 @@
printf("DYNAMIC EXIT: [UOp ");
_PyUOpPrint(&next_uop[-1]);
printf(", exit %u, temp %d, target %d -> %s]\n",
exit - current_executor->exits, exit->temperature.as_counter,
exit - current_executor->exits, exit->temperature.value_and_backoff,
(int)(target - _PyCode_CODE(_PyFrame_GetCode(frame))),
_PyOpcode_OpName[target->op.code]);
}

8
Python/instrumentation.c
View File

@ -643,8 +643,8 @@ de_instrument(PyCodeObject *code, int i, int event)
CHECK(_PyOpcode_Deopt[deinstrumented] == deinstrumented);
FT_ATOMIC_STORE_UINT8_RELAXED(*opcode_ptr, deinstrumented);
if (_PyOpcode_Caches[deinstrumented]) {
FT_ATOMIC_STORE_UINT16_RELAXED(instr[1].counter.as_counter,
adaptive_counter_warmup().as_counter);
FT_ATOMIC_STORE_UINT16_RELAXED(instr[1].counter.value_and_backoff,
adaptive_counter_warmup().value_and_backoff);
}
}
@ -719,8 +719,8 @@ instrument(PyCodeObject *code, int i)
assert(instrumented);
FT_ATOMIC_STORE_UINT8_RELAXED(*opcode_ptr, instrumented);
if (_PyOpcode_Caches[deopt]) {
FT_ATOMIC_STORE_UINT16_RELAXED(instr[1].counter.as_counter,
adaptive_counter_warmup().as_counter);
FT_ATOMIC_STORE_UINT16_RELAXED(instr[1].counter.value_and_backoff,
adaptive_counter_warmup().value_and_backoff);
instr[1].counter = adaptive_counter_warmup();
}
}