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bpo-45527: Don't count cache hits, just misses. (GH-29092)

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Mark Shannon 2021-10-20 19:53:48 +01:00 • committed by GitHub
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commit bc85eb7a4f
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3 changed files with 33 additions and 107 deletions
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47
Include/internal/pycore_code.h
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@ -253,53 +253,6 @@ PyAPI_FUNC(PyObject *) _PyCode_GetVarnames(PyCodeObject *);
PyAPI_FUNC(PyObject *) _PyCode_GetCellvars(PyCodeObject *);
PyAPI_FUNC(PyObject *) _PyCode_GetFreevars(PyCodeObject *);
/* Cache hits and misses */
static inline uint8_t
saturating_increment(uint8_t c)
{
return c<<1;
}
static inline uint8_t
saturating_decrement(uint8_t c)
{
return (c>>1) + 128;
}
static inline uint8_t
saturating_zero(void)
{
return 255;
}
/* Starting value for saturating counter.
* Technically this should be 1, but that is likely to
* cause a bit of thrashing when we optimize then get an immediate miss.
* We want to give the counter a change to stabilize, so we start at 3.
*/
static inline uint8_t
saturating_start(void)
{
return saturating_zero()<<3;
}
static inline void
record_cache_hit(_PyAdaptiveEntry *entry) {
entry->counter = saturating_increment(entry->counter);
}
static inline void
record_cache_miss(_PyAdaptiveEntry *entry) {
entry->counter = saturating_decrement(entry->counter);
}
static inline int
too_many_cache_misses(_PyAdaptiveEntry *entry) {
return entry->counter == saturating_zero();
}
#define ADAPTIVE_CACHE_BACKOFF 64
static inline void