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GH-88691: Shrink the CALL caches #103230

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merged 8 commits into from
Apr 5, 2023
Merged

GH-88691: Shrink the CALL caches #103230

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187f060
Shrink the CALL caches
brandtbucher Mar 25, 2023
ddd0968
Catch up with main
brandtbucher Mar 26, 2023
29928ee
Add another assert
brandtbucher Mar 26, 2023
3282d10
Bump the magic number
brandtbucher Mar 26, 2023
7b6a83e
blurb add
brandtbucher Mar 26, 2023
5d9ca5f
Fix doctest
brandtbucher Mar 26, 2023
d02b607
Get rid of the rest of the CALL cache
brandtbucher Apr 4, 2023
d2ebc2e
Revert "Get rid of the rest of the CALL cache"
brandtbucher Apr 5, 2023
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2 changes: 1 addition & 1 deletion Doc/library/dis.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -59,7 +59,7 @@ the following command can be used to display the disassembly of
3 2 LOAD_GLOBAL 1 (NULL + len)
12 LOAD_FAST 0 (alist)
14 CALL 1
24 RETURN_VALUE
22 RETURN_VALUE

(The "2" is a line number).

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1 change: 0 additions & 1 deletion Include/internal/pycore_code.h
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Expand Up @@ -73,7 +73,6 @@ typedef struct {
typedef struct {
uint16_t counter;
uint16_t func_version[2];
uint16_t min_args;
} _PyCallCache;

#define INLINE_CACHE_ENTRIES_CALL CACHE_ENTRIES(_PyCallCache)
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2 changes: 1 addition & 1 deletion Include/internal/pycore_opcode.h
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3 changes: 2 additions & 1 deletion Lib/importlib/_bootstrap_external.py
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Original file line number Diff line number Diff line change
Expand Up @@ -438,6 +438,7 @@ def _write_atomic(path, data, mode=0o666):
# Python 3.12a7 3522 (Removed JUMP_IF_FALSE_OR_POP/JUMP_IF_TRUE_OR_POP)
# Python 3.12a7 3523 (Convert COMPARE_AND_BRANCH back to COMPARE_OP)
# Python 3.12a7 3524 (Shrink the BINARY_SUBSCR caches)
# Python 3.12b1 3525 (Shrink the CALL caches)

# Python 3.13 will start with 3550

Expand All @@ -454,7 +455,7 @@ def _write_atomic(path, data, mode=0o666):
# Whenever MAGIC_NUMBER is changed, the ranges in the magic_values array
# in PC/launcher.c must also be updated.

MAGIC_NUMBER = (3524).to_bytes(2, 'little') + b'\r\n'
MAGIC_NUMBER = (3525).to_bytes(2, 'little') + b'\r\n'

_RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little') # For import.c

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1 change: 0 additions & 1 deletion Lib/opcode.py
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Expand Up @@ -410,7 +410,6 @@ def pseudo_op(name, op, real_ops):
"CALL": {
"counter": 1,
"func_version": 2,
"min_args": 1,
},
"STORE_SUBSCR": {
"counter": 1,
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258 changes: 129 additions & 129 deletions Lib/test/test_dis.py
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core and Builtins/2023-03-25-23-24-38.gh-issue-88691.2SWBd1.rst
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@@ -0,0 +1 @@
Reduce the number of inline :opcode:`CACHE` entries for :opcode:`CALL`.
66 changes: 33 additions & 33 deletions Programs/test_frozenmain.h
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43 changes: 24 additions & 19 deletions Python/bytecodes.c
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Expand Up @@ -2318,7 +2318,7 @@ dummy_func(
kwnames = GETITEM(frame->f_code->co_consts, oparg);
}

// Cache layout: counter/1, func_version/2, min_args/1
// Cache layout: counter/1, func_version/2
// Neither CALL_INTRINSIC_1/2 nor CALL_FUNCTION_EX are members!
family(call, INLINE_CACHE_ENTRIES_CALL) = {
CALL,
Expand Down Expand Up @@ -2348,7 +2348,7 @@ dummy_func(
// (Some args may be keywords, see KW_NAMES, which sets 'kwnames'.)
// On exit, the stack is [result].
// When calling Python, inline the call using DISPATCH_INLINED().
inst(CALL, (unused/1, unused/2, unused/1, method, callable, args[oparg] -- res)) {
inst(CALL, (unused/1, unused/2, method, callable, args[oparg] -- res)) {
int is_meth = method != NULL;
int total_args = oparg;
if (is_meth) {
Expand Down Expand Up @@ -2426,7 +2426,7 @@ dummy_func(
// Start out with [NULL, bound_method, arg1, arg2, ...]
// Transform to [callable, self, arg1, arg2, ...]
// Then fall through to CALL_PY_EXACT_ARGS
inst(CALL_BOUND_METHOD_EXACT_ARGS, (unused/1, unused/2, unused/1, method, callable, unused[oparg] -- unused)) {
inst(CALL_BOUND_METHOD_EXACT_ARGS, (unused/1, unused/2, method, callable, unused[oparg] -- unused)) {
DEOPT_IF(method != NULL, CALL);
DEOPT_IF(Py_TYPE(callable) != &PyMethod_Type, CALL);
STAT_INC(CALL, hit);
Expand All @@ -2438,7 +2438,7 @@ dummy_func(
GO_TO_INSTRUCTION(CALL_PY_EXACT_ARGS);
}

inst(CALL_PY_EXACT_ARGS, (unused/1, func_version/2, unused/1, method, callable, args[oparg] -- unused)) {
inst(CALL_PY_EXACT_ARGS, (unused/1, func_version/2, method, callable, args[oparg] -- unused)) {
assert(kwnames == NULL);
DEOPT_IF(tstate->interp->eval_frame, CALL);
int is_meth = method != NULL;
Expand All @@ -2465,7 +2465,7 @@ dummy_func(
DISPATCH_INLINED(new_frame);
}

inst(CALL_PY_WITH_DEFAULTS, (unused/1, func_version/2, min_args/1, method, callable, args[oparg] -- unused)) {
inst(CALL_PY_WITH_DEFAULTS, (unused/1, func_version/2, method, callable, args[oparg] -- unused)) {
assert(kwnames == NULL);
DEOPT_IF(tstate->interp->eval_frame, CALL);
int is_meth = method != NULL;
Expand All @@ -2479,6 +2479,11 @@ dummy_func(
PyFunctionObject *func = (PyFunctionObject *)callable;
DEOPT_IF(func->func_version != func_version, CALL);
PyCodeObject *code = (PyCodeObject *)func->func_code;
assert(func->func_defaults);
assert(PyTuple_CheckExact(func->func_defaults));
int defcount = (int)PyTuple_GET_SIZE(func->func_defaults);
assert(defcount <= code->co_argcount);
int min_args = code->co_argcount - defcount;
DEOPT_IF(argcount > code->co_argcount, CALL);
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@markshannon markshannon Apr 5, 2023 •
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Why do we need these checks at all?
I suspect that I added them, but I'm not sure why.

If func->func_version == func_version then the only variable is argcount which is oparg + is_meth.
So we only need to know which of the two possible values of is_meth is safe.
Can precompute those at specialization, so we only need to check is_meth at runtime.

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@brandtbucher brandtbucher Apr 5, 2023 •
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Why do we need these checks at all? I suspect that I added them, but I'm not sure why.

It looks like we just had space for it at the time (when cache sizes were fixed).

If func->func_version == func_version then the only variable is argcount which is oparg + is_meth. So we only need to know which of the two possible values of is_meth is safe. Can precompute those at specialization, so we only need to check is_meth at runtime.

The obvious way to do this would be to split this into two specializations: one that expects is_meth, and one that doesn't.

With that said, I'm not sure it's worth breaking up. There would be a decent amount of code duplication, and this opcode is relatively rare (~0.1% of all instructions executed). So maybe we should just leave it.

(Maybe if we really wanted to, we could use the low bit of the func_version cache entry.)

DEOPT_IF(argcount < min_args, CALL);
DEOPT_IF(!_PyThreadState_HasStackSpace(tstate, code->co_framesize), CALL);
Expand All @@ -2497,7 +2502,7 @@ dummy_func(
DISPATCH_INLINED(new_frame);
}

inst(CALL_NO_KW_TYPE_1, (unused/1, unused/2, unused/1, null, callable, args[oparg] -- res)) {
inst(CALL_NO_KW_TYPE_1, (unused/1, unused/2, null, callable, args[oparg] -- res)) {
assert(kwnames == NULL);
assert(cframe.use_tracing == 0);
assert(oparg == 1);
Expand All @@ -2510,7 +2515,7 @@ dummy_func(
Py_DECREF(&PyType_Type); // I.e., callable
}

inst(CALL_NO_KW_STR_1, (unused/1, unused/2, unused/1, null, callable, args[oparg] -- res)) {
inst(CALL_NO_KW_STR_1, (unused/1, unused/2, null, callable, args[oparg] -- res)) {
assert(kwnames == NULL);
assert(cframe.use_tracing == 0);
assert(oparg == 1);
Expand All @@ -2525,7 +2530,7 @@ dummy_func(
CHECK_EVAL_BREAKER();
}

inst(CALL_NO_KW_TUPLE_1, (unused/1, unused/2, unused/1, null, callable, args[oparg] -- res)) {
inst(CALL_NO_KW_TUPLE_1, (unused/1, unused/2, null, callable, args[oparg] -- res)) {
assert(kwnames == NULL);
assert(oparg == 1);
DEOPT_IF(null != NULL, CALL);
Expand All @@ -2539,7 +2544,7 @@ dummy_func(
CHECK_EVAL_BREAKER();
}

inst(CALL_BUILTIN_CLASS, (unused/1, unused/2, unused/1, method, callable, args[oparg] -- res)) {
inst(CALL_BUILTIN_CLASS, (unused/1, unused/2, method, callable, args[oparg] -- res)) {
int is_meth = method != NULL;
int total_args = oparg;
if (is_meth) {
Expand All @@ -2564,7 +2569,7 @@ dummy_func(
CHECK_EVAL_BREAKER();
}

inst(CALL_NO_KW_BUILTIN_O, (unused/1, unused/2, unused/1, method, callable, args[oparg] -- res)) {
inst(CALL_NO_KW_BUILTIN_O, (unused/1, unused/2, method, callable, args[oparg] -- res)) {
assert(cframe.use_tracing == 0);
/* Builtin METH_O functions */
assert(kwnames == NULL);
Expand Down Expand Up @@ -2596,7 +2601,7 @@ dummy_func(
CHECK_EVAL_BREAKER();
}

inst(CALL_NO_KW_BUILTIN_FAST, (unused/1, unused/2, unused/1, method, callable, args[oparg] -- res)) {
inst(CALL_NO_KW_BUILTIN_FAST, (unused/1, unused/2, method, callable, args[oparg] -- res)) {
assert(cframe.use_tracing == 0);
/* Builtin METH_FASTCALL functions, without keywords */
assert(kwnames == NULL);
Expand Down Expand Up @@ -2632,7 +2637,7 @@ dummy_func(
CHECK_EVAL_BREAKER();
}

inst(CALL_BUILTIN_FAST_WITH_KEYWORDS, (unused/1, unused/2, unused/1, method, callable, args[oparg] -- res)) {
inst(CALL_BUILTIN_FAST_WITH_KEYWORDS, (unused/1, unused/2, method, callable, args[oparg] -- res)) {
assert(cframe.use_tracing == 0);
/* Builtin METH_FASTCALL | METH_KEYWORDS functions */
int is_meth = method != NULL;
Expand Down Expand Up @@ -2668,7 +2673,7 @@ dummy_func(
CHECK_EVAL_BREAKER();
}

inst(CALL_NO_KW_LEN, (unused/1, unused/2, unused/1, method, callable, args[oparg] -- res)) {
inst(CALL_NO_KW_LEN, (unused/1, unused/2, method, callable, args[oparg] -- res)) {
assert(cframe.use_tracing == 0);
assert(kwnames == NULL);
/* len(o) */
Expand Down Expand Up @@ -2696,7 +2701,7 @@ dummy_func(
ERROR_IF(res == NULL, error);
}

inst(CALL_NO_KW_ISINSTANCE, (unused/1, unused/2, unused/1, method, callable, args[oparg] -- res)) {
inst(CALL_NO_KW_ISINSTANCE, (unused/1, unused/2, method, callable, args[oparg] -- res)) {
assert(cframe.use_tracing == 0);
assert(kwnames == NULL);
/* isinstance(o, o2) */
Expand Down Expand Up @@ -2727,7 +2732,7 @@ dummy_func(
}

// This is secretly a super-instruction
inst(CALL_NO_KW_LIST_APPEND, (unused/1, unused/2, unused/1, method, self, args[oparg] -- unused)) {
inst(CALL_NO_KW_LIST_APPEND, (unused/1, unused/2, method, self, args[oparg] -- unused)) {
assert(cframe.use_tracing == 0);
assert(kwnames == NULL);
assert(oparg == 1);
Expand All @@ -2748,7 +2753,7 @@ dummy_func(
DISPATCH();
}

inst(CALL_NO_KW_METHOD_DESCRIPTOR_O, (unused/1, unused/2, unused/1, method, unused, args[oparg] -- res)) {
inst(CALL_NO_KW_METHOD_DESCRIPTOR_O, (unused/1, unused/2, method, unused, args[oparg] -- res)) {
assert(kwnames == NULL);
int is_meth = method != NULL;
int total_args = oparg;
Expand Down Expand Up @@ -2782,7 +2787,7 @@ dummy_func(
CHECK_EVAL_BREAKER();
}

inst(CALL_METHOD_DESCRIPTOR_FAST_WITH_KEYWORDS, (unused/1, unused/2, unused/1, method, unused, args[oparg] -- res)) {
inst(CALL_METHOD_DESCRIPTOR_FAST_WITH_KEYWORDS, (unused/1, unused/2, method, unused, args[oparg] -- res)) {
int is_meth = method != NULL;
int total_args = oparg;
if (is_meth) {
Expand Down Expand Up @@ -2814,7 +2819,7 @@ dummy_func(
CHECK_EVAL_BREAKER();
}

inst(CALL_NO_KW_METHOD_DESCRIPTOR_NOARGS, (unused/1, unused/2, unused/1, method, unused, args[oparg] -- res)) {
inst(CALL_NO_KW_METHOD_DESCRIPTOR_NOARGS, (unused/1, unused/2, method, unused, args[oparg] -- res)) {
assert(kwnames == NULL);
assert(oparg == 0 || oparg == 1);
int is_meth = method != NULL;
Expand Down Expand Up @@ -2846,7 +2851,7 @@ dummy_func(
CHECK_EVAL_BREAKER();
}

inst(CALL_NO_KW_METHOD_DESCRIPTOR_FAST, (unused/1, unused/2, unused/1, method, unused, args[oparg] -- res)) {
inst(CALL_NO_KW_METHOD_DESCRIPTOR_FAST, (unused/1, unused/2, method, unused, args[oparg] -- res)) {
assert(kwnames == NULL);
int is_meth = method != NULL;
int total_args = oparg;
Expand Down
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