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-rw-r--r--Include/cpython/optimizer.h4
-rw-r--r--Misc/NEWS.d/next/Core and Builtins/2023-11-05-06-40-35.gh-issue-111843.c045cB.rst2
-rw-r--r--Python/bytecodes.c23
-rw-r--r--Python/generated_cases.c.h23
-rw-r--r--Python/optimizer.c9
5 files changed, 47 insertions, 14 deletions
diff --git a/Include/cpython/optimizer.h b/Include/cpython/optimizer.h
index 2a5251b..adc2c1f 100644
--- a/Include/cpython/optimizer.h
+++ b/Include/cpython/optimizer.h
@@ -45,6 +45,8 @@ typedef int (*optimize_func)(_PyOptimizerObject* self, PyCodeObject *code, _Py_C
typedef struct _PyOptimizerObject {
PyObject_HEAD
optimize_func optimize;
+ /* These thresholds are treated as signed so do not exceed INT16_MAX
+ * Use INT16_MAX to indicate that the optimizer should never be called */
uint16_t resume_threshold;
uint16_t backedge_threshold;
/* Data needed by the optimizer goes here, but is opaque to the VM */
@@ -76,6 +78,8 @@ PyAPI_FUNC(PyObject *)PyUnstable_Optimizer_NewCounter(void);
PyAPI_FUNC(PyObject *)PyUnstable_Optimizer_NewUOpOptimizer(void);
#define OPTIMIZER_BITS_IN_COUNTER 4
+/* Minimum of 16 additional executions before retry */
+#define MINIMUM_TIER2_BACKOFF 4
#ifdef __cplusplus
}
diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-11-05-06-40-35.gh-issue-111843.c045cB.rst b/Misc/NEWS.d/next/Core and Builtins/2023-11-05-06-40-35.gh-issue-111843.c045cB.rst
new file mode 100644
index 0000000..280f8f9
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2023-11-05-06-40-35.gh-issue-111843.c045cB.rst
@@ -0,0 +1,2 @@
+Use exponential backoff to reduce the number of failed tier 2 optimization
+attempts by over 99%.
diff --git a/Python/bytecodes.c b/Python/bytecodes.c
index 7010042..d914f27 100644
--- a/Python/bytecodes.c
+++ b/Python/bytecodes.c
@@ -2335,10 +2335,12 @@ dummy_func(
JUMPBY(-oparg);
#if ENABLE_SPECIALIZATION
this_instr[1].cache += (1 << OPTIMIZER_BITS_IN_COUNTER);
- if (this_instr[1].cache > tstate->interp->optimizer_backedge_threshold &&
- // Double-check that the opcode isn't instrumented or something:
- this_instr->op.code == JUMP_BACKWARD)
- {
+ /* We are using unsigned values, but we really want signed values, so
+ * do the 2s complement comparison manually */
+ uint16_t ucounter = this_instr[1].cache + (1 << 15);
+ uint16_t threshold = tstate->interp->optimizer_backedge_threshold + (1 << 15);
+ // Double-check that the opcode isn't instrumented or something:
+ if (ucounter > threshold && this_instr->op.code == JUMP_BACKWARD) {
OPT_STAT_INC(attempts);
int optimized = _PyOptimizer_BackEdge(frame, this_instr, next_instr, stack_pointer);
ERROR_IF(optimized < 0, error);
@@ -2346,8 +2348,19 @@ dummy_func(
// Rewind and enter the executor:
assert(this_instr->op.code == ENTER_EXECUTOR);
next_instr = this_instr;
+ this_instr[1].cache &= ((1 << OPTIMIZER_BITS_IN_COUNTER) - 1);
+ }
+ else {
+ int backoff = this_instr[1].cache & ((1 << OPTIMIZER_BITS_IN_COUNTER) - 1);
+ if (backoff < MINIMUM_TIER2_BACKOFF) {
+ backoff = MINIMUM_TIER2_BACKOFF;
+ }
+ else if (backoff < 15 - OPTIMIZER_BITS_IN_COUNTER) {
+ backoff++;
+ }
+ assert(backoff <= 15 - OPTIMIZER_BITS_IN_COUNTER);
+ this_instr[1].cache = ((1 << 16) - ((1 << OPTIMIZER_BITS_IN_COUNTER) << backoff)) | backoff;
}
- this_instr[1].cache &= ((1 << OPTIMIZER_BITS_IN_COUNTER) - 1);
}
#endif /* ENABLE_SPECIALIZATION */
}
diff --git a/Python/generated_cases.c.h b/Python/generated_cases.c.h
index 1c85304..b9a2b22 100644
--- a/Python/generated_cases.c.h
+++ b/Python/generated_cases.c.h
@@ -3409,10 +3409,12 @@
JUMPBY(-oparg);
#if ENABLE_SPECIALIZATION
this_instr[1].cache += (1 << OPTIMIZER_BITS_IN_COUNTER);
- if (this_instr[1].cache > tstate->interp->optimizer_backedge_threshold &&
- // Double-check that the opcode isn't instrumented or something:
- this_instr->op.code == JUMP_BACKWARD)
- {
+ /* We are using unsigned values, but we really want signed values, so
+ * do the 2s complement comparison manually */
+ uint16_t ucounter = this_instr[1].cache + (1 << 15);
+ uint16_t threshold = tstate->interp->optimizer_backedge_threshold + (1 << 15);
+ // Double-check that the opcode isn't instrumented or something:
+ if (ucounter > threshold && this_instr->op.code == JUMP_BACKWARD) {
OPT_STAT_INC(attempts);
int optimized = _PyOptimizer_BackEdge(frame, this_instr, next_instr, stack_pointer);
if (optimized < 0) goto error;
@@ -3420,8 +3422,19 @@
// Rewind and enter the executor:
assert(this_instr->op.code == ENTER_EXECUTOR);
next_instr = this_instr;
+ this_instr[1].cache &= ((1 << OPTIMIZER_BITS_IN_COUNTER) - 1);
+ }
+ else {
+ int backoff = this_instr[1].cache & ((1 << OPTIMIZER_BITS_IN_COUNTER) - 1);
+ if (backoff < MINIMUM_TIER2_BACKOFF) {
+ backoff = MINIMUM_TIER2_BACKOFF;
+ }
+ else if (backoff < 15 - OPTIMIZER_BITS_IN_COUNTER) {
+ backoff++;
+ }
+ assert(backoff <= 15 - OPTIMIZER_BITS_IN_COUNTER);
+ this_instr[1].cache = ((1 << 16) - ((1 << OPTIMIZER_BITS_IN_COUNTER) << backoff)) | backoff;
}
- this_instr[1].cache &= ((1 << OPTIMIZER_BITS_IN_COUNTER) - 1);
}
#endif /* ENABLE_SPECIALIZATION */
DISPATCH();
diff --git a/Python/optimizer.c b/Python/optimizer.c
index 42279be..e142bd0 100644
--- a/Python/optimizer.c
+++ b/Python/optimizer.c
@@ -107,6 +107,7 @@ error_optimize(
_PyExecutorObject **exec,
int Py_UNUSED(stack_entries))
{
+ assert(0);
PyErr_Format(PyExc_SystemError, "Should never call error_optimize");
return -1;
}
@@ -122,8 +123,8 @@ PyTypeObject _PyDefaultOptimizer_Type = {
_PyOptimizerObject _PyOptimizer_Default = {
PyObject_HEAD_INIT(&_PyDefaultOptimizer_Type)
.optimize = error_optimize,
- .resume_threshold = UINT16_MAX,
- .backedge_threshold = UINT16_MAX,
+ .resume_threshold = INT16_MAX,
+ .backedge_threshold = INT16_MAX,
};
_PyOptimizerObject *
@@ -309,7 +310,7 @@ PyUnstable_Optimizer_NewCounter(void)
return NULL;
}
opt->base.optimize = counter_optimize;
- opt->base.resume_threshold = UINT16_MAX;
+ opt->base.resume_threshold = INT16_MAX;
opt->base.backedge_threshold = 0;
opt->count = 0;
return (PyObject *)opt;
@@ -915,7 +916,7 @@ PyUnstable_Optimizer_NewUOpOptimizer(void)
return NULL;
}
opt->optimize = uop_optimize;
- opt->resume_threshold = UINT16_MAX;
+ opt->resume_threshold = INT16_MAX;
// Need at least 3 iterations to settle specializations.
// A few lower bits of the counter are reserved for other flags.
opt->backedge_threshold = 16 << OPTIMIZER_BITS_IN_COUNTER;
generated by cgit v0.12 at 2024-11-22 21:12:57 (GMT)