8000 bpo-45527: Don't count cache hits, just misses. by markshannon · Pull Request #29092 · python/cpython · GitHub
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bpo-45527: Don't count cache hits, just misses. #29092

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Merged
merged 5 commits into from
Oct 20, 2021
Merged

bpo-45527: Don't count cache hits, just misses. #29092

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8406bc7
Do not record cache hits.
markshannon Oct 19, 2021
cf53525
Change start value to 64.
markshannon Oct 19, 2021
ded8288
Cleanup unused code.
markshannon Oct 20, 2021
811b387
Merge branch 'main' into streamline-adaptive-counting
markshannon Oct 20, 2021
8928acd
Explain 53.
markshannon Oct 20, 2021
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Do not record cache hits.
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@markshannon
markshannon committed Oct 20, 2021
commit 8406bc7ab81f7d64a049ef83d836c9936c493186
17 changes: 10 additions & 7 deletions Include/internal/pycore_code.h
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Original file line number Diff line number Diff line change
Expand Up @@ -267,6 +267,7 @@ 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.
Expand All @@ -275,22 +276,24 @@ saturating_zero(void)
static inline uint8_t
saturating_start(void)
{
return saturating_zero()<<3;
return 32;
}

static inline void
record_cache_hit(_PyAdaptiveEntry *entry) {
entry->counter = saturating_increment(entry->counter);
}
// static inline void
// record_cache_hit(_PyAdaptiveEntry *entry) {
// entry->counter = saturating_increment(entry->counter);
// }

#define record_cache_hit(e) ((void)0)

static inline void
record_cache_miss(_PyAdaptiveEntry *entry) {
entry->counter = saturating_decrement(entry->counter);
entry->counter--;
}

static inline int
too_many_cache_misses(_PyAdaptiveEntry *entry) {
return entry->counter == saturating_zero();
return entry->counter == 0;
}

#define ADAPTIVE_CACHE_BACKOFF 64
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16 changes: 9 additions & 7 deletions Python/ceval.c
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Expand Up @@ -1452,11 +1452,13 @@ eval_frame_handle_pending(PyThreadState *tstate)

#define UPDATE_PREV_INSTR_OPARG(instr, oparg) ((uint8_t*)(instr))[-1] = (oparg)

static inline void
record_hit_inline(_Py_CODEUNIT *next_instr, int oparg)
{
UPDATE_PREV_INSTR_OPARG(next_instr, saturating_increment(oparg));
}
// static inline void
// record_hit_inline(_Py_CODEUNIT *next_instr, int oparg)
// {
// UPDATE_PREV_INSTR_OPARG(next_instr, saturating_increment(oparg));
// }

#define record_hit_inline(n, o) ((void)0)

#define GLOBALS() frame->f_globals
#define BUILTINS() frame->f_builtins
Expand Down Expand Up @@ -5115,10 +5117,10 @@ opname ## _miss: \
opname ## _miss: \
{ \
STAT_INC(opname, miss); \
uint8_t oparg = saturating_decrement(_Py_OPARG(next_instr[-1])); \
uint8_t oparg = _Py_OPARG(next_instr[-1])-1; \
UPDATE_PREV_INSTR_OPARG(next_instr, oparg); \
assert(_Py_OPARG(next_instr[-1]) == oparg); \
if (oparg == saturating_zero()) /* too many cache misses */ { \
if (oparg == 0) /* too many cache misses */ { \
oparg = ADAPTIVE_CACHE_BACKOFF; \
next_instr[-1] = _Py_MAKECODEUNIT(opname ## _ADAPTIVE, oparg); \
STAT_INC(opname, deopt); \
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0