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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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GPG key ID: B5690EEEBB952194
19 changed files with 313 additions and 235 deletions
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31
Python/ceval_macros.h
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@ -262,7 +262,7 @@ GETITEM(PyObject *v, Py_ssize_t i) {
STAT_INC(opcode, miss); \
STAT_INC((INSTNAME), miss); \
/* The counter is always the first cache entry: */ \
if (ADAPTIVE_COUNTER_IS_ZERO(next_instr->cache)) { \
if (ADAPTIVE_COUNTER_TRIGGERS(next_instr->cache)) { \
STAT_INC((INSTNAME), deopt); \
} \
} while (0)
@ -290,29 +290,28 @@ GETITEM(PyObject *v, Py_ssize_t i) {
dtrace_function_entry(frame); \
}
#define ADAPTIVE_COUNTER_IS_ZERO(COUNTER) \
(((COUNTER) >> ADAPTIVE_BACKOFF_BITS) == 0)
#define ADAPTIVE_COUNTER_IS_MAX(COUNTER) \
(((COUNTER) >> ADAPTIVE_BACKOFF_BITS) == ((1 << MAX_BACKOFF_VALUE) - 1))
/* This takes a uint16_t instead of a _Py_BackoffCounter,
* because it is used directly on the cache entry in generated code,
* which is always an integral type. */
#define ADAPTIVE_COUNTER_TRIGGERS(COUNTER) \
backoff_counter_triggers(forge_backoff_counter((COUNTER)))
#ifdef Py_GIL_DISABLED
#define DECREMENT_ADAPTIVE_COUNTER(COUNTER) \
do { \
/* gh-115999 tracks progress on addressing this. */ \
#define ADVANCE_ADAPTIVE_COUNTER(COUNTER) \
do { \
/* gh-115999 tracks progress on addressing this. */ \
static_assert(0, "The specializing interpreter is not yet thread-safe"); \
} while (0);
#else
#define DECREMENT_ADAPTIVE_COUNTER(COUNTER) \
do { \
assert(!ADAPTIVE_COUNTER_IS_ZERO((COUNTER))); \
(COUNTER) -= (1 << ADAPTIVE_BACKOFF_BITS); \
#define ADVANCE_ADAPTIVE_COUNTER(COUNTER) \
do { \
(COUNTER) = advance_backoff_counter((COUNTER)); \
} while (0);
#endif
#define INCREMENT_ADAPTIVE_COUNTER(COUNTER) \
do { \
(COUNTER) += (1 << ADAPTIVE_BACKOFF_BITS); \
#define PAUSE_ADAPTIVE_COUNTER(COUNTER) \
do { \
(COUNTER) = pause_backoff_counter((COUNTER)); \
} while (0);
#define UNBOUNDLOCAL_ERROR_MSG \