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gh-116968: Reimplement Tier 2 counters (#117144)

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Introduce a unified 16-bit backoff counter type (``_Py_BackoffCounter``),
shared between the Tier 1 adaptive specializer and the Tier 2 optimizer. The
API used for adaptive specialization counters is changed but the behavior is
(supposed to be) identical.

The behavior of the Tier 2 counters is changed:
- There are no longer dynamic thresholds (we never varied these).
- All counters now use the same exponential backoff.
- The counter for ``JUMP_BACKWARD`` starts counting down from 16.
- The ``temperature`` in side exits starts counting down from 64.
This commit is contained in:
Guido van Rossum 2024-04-04 08:03:27 -07:00 • committed by GitHub
parent 63bbe77d9b
commit 060a96f1a9
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19 changed files with 313 additions and 235 deletions
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11
Python/executor_cases.c.h generated
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@ -3694,21 +3694,22 @@
oparg = CURRENT_OPARG();
_PyExecutorObject *previous = (_PyExecutorObject *)tstate->previous_executor;
_PyExitData *exit = &previous->exits[oparg];
exit->temperature++;
PyCodeObject *code = _PyFrame_GetCode(frame);
_Py_CODEUNIT *target = _PyCode_CODE(code) + exit->target;
if (exit->temperature < (int32_t)tstate->interp->optimizer_side_threshold) {
_Py_BackoffCounter temperature = exit->temperature;
if (!backoff_counter_triggers(temperature)) {
exit->temperature = advance_backoff_counter(temperature);
GOTO_TIER_ONE(target);
}
_PyExecutorObject *executor;
if (target->op.code == ENTER_EXECUTOR) {
executor = code->co_executors->executors[target->op.arg];
Py_INCREF(executor);
} else {
}
else {
int optimized = _PyOptimizer_Optimize(frame, target, stack_pointer, &executor);
if (optimized <= 0) {
int32_t new_temp = -1 * tstate->interp->optimizer_side_threshold;
exit->temperature = (new_temp < INT16_MIN) ? INT16_MIN : new_temp;
exit->temperature = restart_backoff_counter(temperature);
if (optimized < 0) {
Py_DECREF(previous);
tstate->previous_executor = Py_None;