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mimalloc/src/bitmap.c
daanx e43eb1f191 nicer debug output
2024-12-12 20:22:24 -08:00

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/* ----------------------------------------------------------------------------
Copyright (c) 2019-2024 Microsoft Research, Daan Leijen
This is free software; you can redistribute it and/or modify it under the
terms of the MIT license. A copy of the license can be found in the file
"LICENSE" at the root of this distribution.
-----------------------------------------------------------------------------*/
/* ----------------------------------------------------------------------------
Concurrent bitmap that can set/reset sequences of bits atomically
---------------------------------------------------------------------------- */
#include "mimalloc.h"
#include "mimalloc/internal.h"
#include "mimalloc/bits.h"
#include "bitmap.h"
#ifndef MI_OPT_SIMD
#define MI_OPT_SIMD 0
#endif
/* --------------------------------------------------------------------------------
bfields
-------------------------------------------------------------------------------- */
static inline size_t mi_bfield_ctz(mi_bfield_t x) {
return mi_ctz(x);
}
static inline size_t mi_bfield_popcount(mi_bfield_t x) {
return mi_popcount(x);
}
static inline mi_bfield_t mi_bfield_clear_least_bit(mi_bfield_t x) {
return (x & (x-1));
}
// find the least significant bit that is set (i.e. count trailing zero's)
// return false if `x==0` (with `*idx` undefined) and true otherwise,
// with the `idx` is set to the bit index (`0 <= *idx < MI_BFIELD_BITS`).
static inline bool mi_bfield_find_least_bit(mi_bfield_t x, size_t* idx) {
return mi_bsf(x,idx);
}
// find each set bit in a bit field `x` until it becomes zero.
static inline bool mi_bfield_foreach_bit(mi_bfield_t* x, size_t* idx) {
const bool found = mi_bfield_find_least_bit(*x, idx);
*x = mi_bfield_clear_least_bit(*x);
return found;
}
//static inline mi_bfield_t mi_bfield_rotate_right(mi_bfield_t x, size_t r) {
// return mi_rotr(x,r);
//}
static inline mi_bfield_t mi_bfield_zero(void) {
return 0;
}
static inline mi_bfield_t mi_bfield_one(void) {
return 1;
}
static inline mi_bfield_t mi_bfield_all_set(void) {
return ~((mi_bfield_t)0);
}
static inline mi_bfield_t mi_bfield_mask(size_t bit_count, size_t shiftl) {
mi_assert_internal(bit_count > 0);
mi_assert_internal(bit_count + shiftl <= MI_BFIELD_BITS);
const mi_bfield_t mask0 = (bit_count < MI_BFIELD_BITS ? (mi_bfield_one() << bit_count)-1 : mi_bfield_all_set());
return (mask0 << shiftl);
}
// ------- mi_bfield_atomic_set ---------------------------------------
// Set a bit atomically. Returns `true` if the bit transitioned from 0 to 1
static inline bool mi_bfield_atomic_set(_Atomic(mi_bfield_t)*b, size_t idx) {
mi_assert_internal(idx < MI_BFIELD_BITS);
const mi_bfield_t mask = mi_bfield_one()<<idx;
const mi_bfield_t old = mi_atomic_or_acq_rel(b, mask);
return ((old&mask) == 0);
}
// Clear a bit atomically. Returns `true` if the bit transitioned from 1 to 0.
// `all_clear` is set if the new bfield is zero.
static inline bool mi_bfield_atomic_clear(_Atomic(mi_bfield_t)*b, size_t idx, bool* all_clear) {
mi_assert_internal(idx < MI_BFIELD_BITS);
const mi_bfield_t mask = mi_bfield_one()<<idx;
mi_bfield_t old = mi_atomic_and_acq_rel(b, ~mask);
if (all_clear != NULL) { *all_clear = ((old&~mask)==0); }
return ((old&mask) == mask);
}
// Clear a bit but only when/once it is set. This is used by concurrent free's while
// the page is abandoned and mapped.
static inline void mi_bfield_atomic_clear_once_set(_Atomic(mi_bfield_t)*b, size_t idx) {
mi_assert_internal(idx < MI_BFIELD_BITS);
const mi_bfield_t mask = mi_bfield_one()<<idx;
mi_bfield_t old = mi_atomic_load_relaxed(b);
do {
if mi_unlikely((old&mask) == 0) {
old = mi_atomic_load_acquire(b);
if ((old&mask)==0) { _mi_stat_counter_increase(&_mi_stats_main.pages_unabandon_busy_wait, 1); }
while ((old&mask)==0) { // busy wait
mi_atomic_yield();
old = mi_atomic_load_acquire(b);
}
}
} while (!mi_atomic_cas_weak_acq_rel(b,&old, (old&~mask)));
mi_assert_internal((old&mask)==mask); // we should only clear when it was set
}
// Set a mask set of bits atomically, and return true of the mask bits transitioned from all 0's to 1's.
static inline bool mi_bfield_atomic_set_mask(_Atomic(mi_bfield_t)*b, mi_bfield_t mask, size_t* already_set) {
mi_assert_internal(mask != 0);
mi_bfield_t old = mi_atomic_load_relaxed(b);
while (!mi_atomic_cas_weak_acq_rel(b, &old, old|mask)) { }; // try to atomically set the mask bits until success
if (already_set!=NULL) { *already_set = mi_bfield_popcount(old&mask); }
return ((old&mask) == 0);
}
// Clear a mask set of bits atomically, and return true of the mask bits transitioned from all 1's to 0's
static inline bool mi_bfield_atomic_clear_mask(_Atomic(mi_bfield_t)*b, mi_bfield_t mask, size_t* already_clear) {
mi_assert_internal(mask != 0);
mi_bfield_t old = mi_atomic_load_relaxed(b);
while (!mi_atomic_cas_weak_acq_rel(b, &old, old&~mask)) { }; // try to atomically clear the mask bits until success
if (already_clear!=NULL) { *already_clear = mi_bfield_popcount(~(old&mask)); }
return ((old&mask) == mask);
}
// Set/clear a mask set of bits atomically, and return true of the mask bits transitioned from all 0's to 1's (or all 1's to 0's)
static inline bool mi_bfield_atomic_xset_mask(mi_xset_t set, _Atomic(mi_bfield_t)*b, mi_bfield_t mask, size_t* already_xset) {
mi_assert_internal(mask != 0);
if (set) {
return mi_bfield_atomic_set_mask(b, mask, already_xset);
}
else {
return mi_bfield_atomic_clear_mask(b, mask, already_xset);
}
}
static inline bool mi_bfield_atomic_set8(_Atomic(mi_bfield_t)*b, size_t byte_idx) {
mi_assert_internal(byte_idx < MI_BFIELD_SIZE);
const mi_bfield_t mask = ((mi_bfield_t)0xFF)<<(byte_idx*8);
return mi_bfield_atomic_xset_mask(MI_BIT_SET, b, mask, NULL);
}
static inline bool mi_bfield_atomic_clear8(_Atomic(mi_bfield_t)*b, size_t byte_idx, bool* all_clear) {
mi_assert_internal(byte_idx < MI_BFIELD_SIZE);
const mi_bfield_t mask = ((mi_bfield_t)0xFF)<<(byte_idx*8);
mi_bfield_t old = mi_atomic_load_relaxed(b);
while (!mi_atomic_cas_weak_acq_rel(b, &old, old&~mask)) {}; // try to atomically clear the mask bits until success
if (all_clear!=NULL) { *all_clear = ((old&~mask)==0); }
return ((old&mask) == mask);
}
static inline bool mi_bfield_atomic_setX(_Atomic(mi_bfield_t)*b) {
const mi_bfield_t old = mi_atomic_exchange_release(b, mi_bfield_all_set());
return (old==0);
}
static inline bool mi_bfield_atomic_clearX(_Atomic(mi_bfield_t)*b) {
const mi_bfield_t old = mi_atomic_exchange_release(b, mi_bfield_zero());
return (~old==0);
}
// ------- mi_bfield_atomic_try_xset ---------------------------------------
// Tries to set a mask atomically, and returns true if the mask bits atomically transitioned from 0 to mask
// and false otherwise (leaving the bit field as is).
static inline bool mi_bfield_atomic_try_set_mask(_Atomic(mi_bfield_t)*b, mi_bfield_t mask) {
mi_assert_internal(mask != 0);
mi_bfield_t old = mi_atomic_load_relaxed(b);
do {
if ((old&mask) != 0) return false; // the mask bits are no longer 0
} while (!mi_atomic_cas_weak_acq_rel(b, &old, old|mask)); // try to atomically set the mask bits
return true;
}
// Tries to clear a mask atomically, and returns true if the mask bits atomically transitioned from mask to 0
// and false otherwise (leaving the bit field as is).
static inline bool mi_bfield_atomic_try_clear_mask(_Atomic(mi_bfield_t)*b, mi_bfield_t mask, bool* all_clear) {
mi_assert_internal(mask != 0);
mi_bfield_t old = mi_atomic_load_relaxed(b);
do {
if ((old&mask) != mask) {
// the mask bits are no longer set
if (all_clear != NULL) { *all_clear = (old==0); }
return false;
}
} while (!mi_atomic_cas_weak_acq_rel(b, &old, old&~mask)); // try to atomically clear the mask bits
if (all_clear != NULL) { *all_clear = ((old&~mask) == 0); }
return true;
}
// Tries to clear a bit atomically. Returns `true` if the bit transitioned from 1 to 0.
// `all_clear` is set to true if the new bfield is zero (and false otherwise)
static inline bool mi_bfield_atomic_try_clear(_Atomic(mi_bfield_t)*b, size_t idx, bool* all_clear) {
mi_assert_internal(idx < MI_BFIELD_BITS);
const mi_bfield_t mask = mi_bfield_one()<<idx;
return mi_bfield_atomic_try_clear_mask(b,mask,all_clear);
// const mi_bfield_t old = mi_atomic_and_acq_rel(b, ~mask);
// if (all_clear != NULL) { *all_clear = ((old&~mask)==0); }
// return ((old&mask) == mask);
}
// Tries to (un)set a mask atomically, and returns true if the mask bits atomically transitioned from 0 to mask (or mask to 0)
// and false otherwise (leaving the bit field as is).
static inline bool mi_bfield_atomic_try_xset_mask(mi_xset_t set, _Atomic(mi_bfield_t)* b, mi_bfield_t mask, bool* all_clear ) {
mi_assert_internal(mask != 0);
if (set) {
if (all_clear != NULL) { *all_clear = false; }
return mi_bfield_atomic_try_set_mask(b, mask);
}
else {
return mi_bfield_atomic_try_clear_mask(b, mask, all_clear);
}
}
// Tries to clear a byte atomically, and returns true if the byte atomically transitioned from 0xFF to 0
static inline bool mi_bfield_atomic_try_clear8(_Atomic(mi_bfield_t)*b, size_t byte_idx, bool* all_clear) {
mi_assert_internal(byte_idx < MI_BFIELD_SIZE);
const mi_bfield_t mask = ((mi_bfield_t)0xFF)<<(byte_idx*8);
return mi_bfield_atomic_try_clear_mask(b, mask, all_clear);
}
// Try to clear a full field of bits atomically, and return true all bits transitioned from all 1's to 0's.
// and false otherwise leaving the bit field as-is.
static inline bool mi_bfield_atomic_try_clearX(_Atomic(mi_bfield_t)*b) {
mi_bfield_t old = mi_bfield_all_set();
return mi_atomic_cas_strong_acq_rel(b, &old, mi_bfield_zero());
}
// ------- mi_bfield_atomic_is_set ---------------------------------------
// Check if all bits corresponding to a mask are set.
static inline bool mi_bfield_atomic_is_set_mask(_Atomic(mi_bfield_t)*b, mi_bfield_t mask) {
mi_assert_internal(mask != 0);
return ((*b & mask) == mask);
}
// Check if all bits corresponding to a mask are clear.
static inline bool mi_bfield_atomic_is_clear_mask(_Atomic(mi_bfield_t)*b, mi_bfield_t mask) {
mi_assert_internal(mask != 0);
return ((*b & mask) == 0);
}
// Check if all bits corresponding to a mask are set/cleared.
static inline bool mi_bfield_atomic_is_xset_mask(mi_xset_t set, _Atomic(mi_bfield_t)*b, mi_bfield_t mask) {
mi_assert_internal(mask != 0);
if (set) {
return mi_bfield_atomic_is_set_mask(b, mask);
}
else {
return mi_bfield_atomic_is_clear_mask(b, mask);
}
}
/* --------------------------------------------------------------------------------
bitmap chunks
-------------------------------------------------------------------------------- */
// ------- mi_bchunk_xset ---------------------------------------
static inline bool mi_bchunk_set(mi_bchunk_t* chunk, size_t cidx) {
mi_assert_internal(cidx < MI_BCHUNK_BITS);
const size_t i = cidx / MI_BFIELD_BITS;
const size_t idx = cidx % MI_BFIELD_BITS;
return mi_bfield_atomic_set(&chunk->bfields[i], idx);
}
static inline bool mi_bchunk_clear(mi_bchunk_t* chunk, size_t cidx, bool* maybe_all_clear) {
mi_assert_internal(cidx < MI_BCHUNK_BITS);
const size_t i = cidx / MI_BFIELD_BITS;
const size_t idx = cidx % MI_BFIELD_BITS;
return mi_bfield_atomic_clear(&chunk->bfields[i], idx, maybe_all_clear);
}
static inline bool mi_bchunk_set8(mi_bchunk_t* chunk, size_t byte_idx) {
mi_assert_internal(byte_idx < MI_BCHUNK_SIZE);
const size_t i = byte_idx / MI_BFIELD_SIZE;
const size_t bidx = byte_idx % MI_BFIELD_SIZE;
return mi_bfield_atomic_set8(&chunk->bfields[i], bidx);
}
static inline bool mi_bchunk_clear8(mi_bchunk_t* chunk, size_t byte_idx, bool* maybe_all_clear) {
mi_assert_internal(byte_idx < MI_BCHUNK_SIZE);
const size_t i = byte_idx / MI_BFIELD_SIZE;
const size_t bidx = byte_idx % MI_BFIELD_SIZE;
return mi_bfield_atomic_clear8(&chunk->bfields[i], bidx, maybe_all_clear);
}
static inline bool mi_bchunk_setX(mi_bchunk_t* chunk, size_t field_idx) {
mi_assert_internal(field_idx < MI_BCHUNK_FIELDS);
return mi_bfield_atomic_setX(&chunk->bfields[field_idx]);
}
static inline bool mi_bchunk_clearX(mi_bchunk_t* chunk, size_t field_idx, bool* maybe_all_clear) {
mi_assert_internal(field_idx < MI_BCHUNK_FIELDS);
if (maybe_all_clear != NULL) { *maybe_all_clear = true; }
return mi_bfield_atomic_clearX(&chunk->bfields[field_idx]);
}
// Set/clear a sequence of `n` bits within a chunk.
// Returns true if all bits transitioned from 0 to 1 (or 1 to 0).
static bool mi_bchunk_xsetN(mi_xset_t set, mi_bchunk_t* chunk, size_t cidx, size_t n, size_t* palready_xset) {
mi_assert_internal(cidx + n <= MI_BCHUNK_BITS);
mi_assert_internal(n>0);
bool all_transition = true;
size_t total_already_xset = 0;
size_t idx = cidx % MI_BFIELD_BITS;
size_t field = cidx / MI_BFIELD_BITS;
while (n > 0) {
size_t m = MI_BFIELD_BITS - idx; // m is the bits to xset in this field
if (m > n) { m = n; }
mi_assert_internal(idx + m <= MI_BFIELD_BITS);
mi_assert_internal(field < MI_BCHUNK_FIELDS);
const mi_bfield_t mask = mi_bfield_mask(m, idx);
size_t already_xset = 0;
const bool transition = mi_bfield_atomic_xset_mask(set, &chunk->bfields[field], mask, &already_xset);
mi_assert_internal((transition && already_xset == 0) || (!transition && already_xset > 0));
all_transition = all_transition && transition;
total_already_xset += already_xset;
// next field
field++;
idx = 0;
n -= m;
}
if (palready_xset!=NULL) { *palready_xset = total_already_xset; }
return all_transition;
}
static inline bool mi_bchunk_setN(mi_bchunk_t* chunk, size_t cidx, size_t n, size_t* already_set) {
return mi_bchunk_xsetN(MI_BIT_SET, chunk, cidx, n, already_set);
}
static inline bool mi_bchunk_clearN(mi_bchunk_t* chunk, size_t cidx, size_t n, size_t* already_clear) {
return mi_bchunk_xsetN(MI_BIT_CLEAR, chunk, cidx, n, already_clear);
}
// ------- mi_bchunk_is_xset ---------------------------------------
// Check if a sequence of `n` bits within a chunk are all set/cleared.
// This can cross bfield's
mi_decl_noinline static bool mi_bchunk_is_xsetN_(mi_xset_t set, mi_bchunk_t* chunk, size_t field_idx, size_t idx, size_t n) {
mi_assert_internal((field_idx*MI_BFIELD_BITS) + idx + n <= MI_BCHUNK_BITS);
while (n > 0) {
size_t m = MI_BFIELD_BITS - idx; // m is the bits to xset in this field
if (m > n) { m = n; }
mi_assert_internal(idx + m <= MI_BFIELD_BITS);
mi_assert_internal(field_idx < MI_BCHUNK_FIELDS);
const size_t mask = mi_bfield_mask(m, idx);
if (!mi_bfield_atomic_is_xset_mask(set, &chunk->bfields[field_idx], mask)) {
return false;
}
// next field
field_idx++;
idx = 0;
n -= m;
}
return true;
}
// Check if a sequence of `n` bits within a chunk are all set/cleared.
static inline bool mi_bchunk_is_xsetN(mi_xset_t set, mi_bchunk_t* chunk, size_t cidx, size_t n) {
mi_assert_internal(cidx + n <= MI_BCHUNK_BITS);
mi_assert_internal(n>0);
if (n==0) return true;
size_t field = cidx / MI_BFIELD_BITS;
size_t idx = cidx % MI_BFIELD_BITS;
if mi_likely(n<=MI_BFIELD_BITS) {
return mi_bfield_atomic_is_xset_mask(set, &chunk->bfields[field], mi_bfield_mask(n, idx));
}
else {
return mi_bchunk_is_xsetN_(set, chunk, field, idx, n);
}
}
// ------- mi_bchunk_try_xset ---------------------------------------
// Try to atomically set/clear a sequence of `n` bits within a chunk.
// Returns true if all bits transitioned from 0 to 1 (or 1 to 0),
// and false otherwise leaving all bit fields as is.
static bool mi_bchunk_try_xsetN(mi_xset_t set, mi_bchunk_t* chunk, size_t cidx, size_t n, bool* pmaybe_all_clear) {
mi_assert_internal(cidx + n <= MI_BCHUNK_BITS);
mi_assert_internal(n>0);
if (n==0) return true;
size_t start_idx = cidx % MI_BFIELD_BITS;
size_t start_field = cidx / MI_BFIELD_BITS;
size_t end_field = MI_BCHUNK_FIELDS;
mi_bfield_t mask_mid = 0;
mi_bfield_t mask_end = 0;
bool field_is_clear;
bool maybe_all_clear = true;
if (pmaybe_all_clear != NULL) { *pmaybe_all_clear = false; }
// first field
size_t field = start_field;
size_t m = MI_BFIELD_BITS - start_idx; // m is the bits to xset in this field
if (m > n) { m = n; }
mi_assert_internal(start_idx + m <= MI_BFIELD_BITS);
mi_assert_internal(start_field < MI_BCHUNK_FIELDS);
const mi_bfield_t mask_start = mi_bfield_mask(m, start_idx);
if (!mi_bfield_atomic_try_xset_mask(set, &chunk->bfields[field], mask_start, &field_is_clear)) return false;
maybe_all_clear = maybe_all_clear && field_is_clear;
// done?
n -= m;
if (n==0) {
if (pmaybe_all_clear != NULL) { *pmaybe_all_clear = maybe_all_clear; }
return true;
}
// continue with mid fields and last field: if these fail we need to recover by unsetting previous fields
// mid fields
while (n >= MI_BFIELD_BITS) {
field++;
mi_assert_internal(field < MI_BCHUNK_FIELDS);
mask_mid = mi_bfield_all_set();
if (!mi_bfield_atomic_try_xset_mask(set, &chunk->bfields[field], mask_mid, &field_is_clear)) goto restore;
maybe_all_clear = maybe_all_clear && field_is_clear;
n -= MI_BFIELD_BITS;
}
// last field
if (n > 0) {
mi_assert_internal(n < MI_BFIELD_BITS);
field++;
mi_assert_internal(field < MI_BCHUNK_FIELDS);
end_field = field;
mask_end = mi_bfield_mask(n, 0);
if (!mi_bfield_atomic_try_xset_mask(set, &chunk->bfields[field], mask_end, &field_is_clear)) goto restore;
maybe_all_clear = maybe_all_clear && field_is_clear;
}
if (pmaybe_all_clear != NULL) { *pmaybe_all_clear = maybe_all_clear; }
return true;
restore:
// field is on the field that failed to set atomically; we need to restore all previous fields
mi_assert_internal(field > start_field);
while( field > start_field) {
field--;
const size_t mask = (field == start_field ? mask_start : (field == end_field ? mask_end : mask_mid));
mi_bfield_atomic_xset_mask(!set, &chunk->bfields[field], mask, NULL);
}
return false;
}
// static inline bool mi_bchunk_try_setN(mi_bchunk_t* chunk, size_t cidx, size_t n) {
// return mi_bchunk_try_xsetN(MI_BIT_SET, chunk, cidx, n, NULL);
// }
static inline bool mi_bchunk_try_clearN(mi_bchunk_t* chunk, size_t cidx, size_t n, bool* maybe_all_clear) {
return mi_bchunk_try_xsetN(MI_BIT_CLEAR, chunk, cidx, n, maybe_all_clear);
}
// ------- mi_bchunk_try_find_and_clear ---------------------------------------
#if MI_OPT_SIMD && defined(__AVX2__)
static inline __m256i mi_mm256_zero(void) {
return _mm256_setzero_si256();
}
static inline __m256i mi_mm256_ones(void) {
return _mm256_set1_epi64x(~0);
}
//static inline bool mi_mm256_is_ones(__m256i vec) {
// return _mm256_testc_si256(vec, _mm256_cmpeq_epi32(vec, vec));
//}
static inline bool mi_mm256_is_zero( __m256i vec) {
return _mm256_testz_si256(vec,vec);
}
#endif
static inline bool mi_bchunk_try_find_and_clear_at(mi_bchunk_t* chunk, size_t chunk_idx, size_t* pidx, bool allow_allset) {
mi_assert_internal(chunk_idx < MI_BCHUNK_FIELDS);
const mi_bfield_t b = mi_atomic_load_relaxed(&chunk->bfields[chunk_idx]);
size_t cidx;
if (!allow_allset && (~b == 0)) return false;
if (mi_bfield_find_least_bit(b, &cidx)) { // find the least bit
if mi_likely(mi_bfield_atomic_try_clear(&chunk->bfields[chunk_idx], cidx, NULL)) { // clear it atomically
*pidx = (chunk_idx*MI_BFIELD_BITS) + cidx;
mi_assert_internal(*pidx < MI_BCHUNK_BITS);
return true;
}
}
return false;
}
// Find least 1-bit in a chunk and try to clear it atomically
// set `*pidx` to the bit index (0 <= *pidx < MI_BCHUNK_BITS) on success.
// This is used to find free slices and abandoned pages and should be efficient.
// todo: try neon version
static inline bool mi_bchunk_try_find_and_clear(mi_bchunk_t* chunk, size_t* pidx) {
#if MI_OPT_SIMD && defined(__AVX2__) && (MI_BCHUNK_BITS==256)
while (true) {
const __m256i vec = _mm256_load_si256((const __m256i*)chunk->bfields);
const __m256i vcmp = _mm256_cmpeq_epi64(vec, mi_mm256_zero()); // (elem64 == 0 ? 0xFF : 0)
const uint32_t mask = ~_mm256_movemask_epi8(vcmp); // mask of most significant bit of each byte (so each 8 bits are all set or clear)
// mask is inverted, so each 8-bits is 0xFF iff the corresponding elem64 has a bit set (and thus can be cleared)
if (mask==0) return false;
mi_assert_internal((_tzcnt_u32(mask)%8) == 0); // tzcnt == 0, 8, 16, or 24
const size_t chunk_idx = _tzcnt_u32(mask) / 8;
if (mi_bchunk_try_find_and_clear_at(chunk, chunk_idx, pidx, true)) return true;
// try again
}
#elif MI_OPT_SIMD && defined(__AVX2__) && (MI_BCHUNK_BITS==512)
while (true) {
size_t chunk_idx = 0;
#if 0
// one vector at a time
__m256i vec = _mm256_load_si256((const __m256i*)chunk->bfields);
if (mi_mm256_is_zero(vec)) {
chunk_idx += 4;
vec = _mm256_load_si256(((const __m256i*)chunk->bfields) + 1);
}
const __m256i vcmp = _mm256_cmpeq_epi64(vec, mi_mm256_zero()); // (elem64 == 0 ? 0xFF : 0)
const uint32_t mask = ~_mm256_movemask_epi8(vcmp); // mask of most significant bit of each byte (so each 8 bits are all set or clear)
// mask is inverted, so each 8-bits is 0xFF iff the corresponding elem64 has a bit set (and thus can be cleared)
if (mask==0) return false;
mi_assert_internal((_tzcnt_u32(mask)%8) == 0); // tzcnt == 0, 8, 16, or 24
chunk_idx += _tzcnt_u32(mask) / 8;
#else
// a cache line is 64b so we can just as well load all at the same time
const __m256i vec1 = _mm256_load_si256((const __m256i*)chunk->bfields);
const __m256i vec2 = _mm256_load_si256(((const __m256i*)chunk->bfields)+1);
const __m256i cmpv = mi_mm256_zero();
const __m256i vcmp1 = _mm256_cmpeq_epi64(vec1, cmpv); // (elem64 == 0 ? 0xFF : 0)
const __m256i vcmp2 = _mm256_cmpeq_epi64(vec2, cmpv); // (elem64 == 0 ? 0xFF : 0)
const uint32_t mask1 = ~_mm256_movemask_epi8(vcmp1); // mask of most significant bit of each byte (so each 8 bits are all set or clear)
const uint32_t mask2 = ~_mm256_movemask_epi8(vcmp2); // mask of most significant bit of each byte (so each 8 bits are all set or clear)
const uint64_t mask = ((uint64_t)mask2 << 32) | mask1;
// mask is inverted, so each 8-bits is 0xFF iff the corresponding elem64 has a bit set (and thus can be cleared)
if (mask==0) return false;
mi_assert_internal((_tzcnt_u64(mask)%8) == 0); // tzcnt == 0, 8, 16, 24 , ..
chunk_idx = mi_ctz(mask) / 8;
#endif
if (mi_bchunk_try_find_and_clear_at(chunk, chunk_idx, pidx, true)) return true;
// try again
}
#else
// try first to find a field that is not all set (to reduce fragmentation)
for (int i = 0; i < MI_BCHUNK_FIELDS; i++) {
if (mi_bchunk_try_find_and_clear_at(chunk, i, pidx, false /* don't consider allset fields */)) return true;
}
for (int i = 0; i < MI_BCHUNK_FIELDS; i++) {
if (mi_bchunk_try_find_and_clear_at(chunk, i, pidx, true)) return true;
}
return false;
#endif
}
static inline bool mi_bchunk_try_find_and_clear_1(mi_bchunk_t* chunk, size_t n, size_t* pidx) {
mi_assert_internal(n==1); MI_UNUSED(n);
return mi_bchunk_try_find_and_clear(chunk, pidx);
}
#if !MI_OPT_SIMD
static inline bool mi_bchunk_try_find_and_clear8_at(mi_bchunk_t* chunk, size_t chunk_idx, size_t* pidx, bool allow_all_set) {
const mi_bfield_t b = mi_atomic_load_relaxed(&chunk->bfields[chunk_idx]);
if (!allow_all_set && (~b == 0)) return false;
// has_set8 has low bit in each byte set if the byte in x == 0xFF
const mi_bfield_t has_set8 =
((~b - MI_BFIELD_LO_BIT8) & // high bit set if byte in x is 0xFF or < 0x7F
(b & MI_BFIELD_HI_BIT8)) // high bit set if byte in x is >= 0x80
>> 7; // shift high bit to low bit
size_t idx;
if (mi_bfield_find_least_bit(has_set8, &idx)) { // find least 1-bit
mi_assert_internal(idx <= (MI_BFIELD_BITS - 8));
mi_assert_internal((idx%8)==0);
const size_t byte_idx = idx/8;
if mi_likely(mi_bfield_atomic_try_clear8(&chunk->bfields[chunk_idx], byte_idx, NULL)) { // unset the byte atomically
*pidx = (chunk_idx*MI_BFIELD_BITS) + idx;
mi_assert_internal(*pidx + 8 <= MI_BCHUNK_BITS);
return true;
}
}
return false;
}
#endif
// find least byte in a chunk with all bits set, and try unset it atomically
// set `*pidx` to its bit index (0 <= *pidx < MI_BCHUNK_BITS) on success.
// Used to find medium size pages in the free blocks.
// todo: try neon version
static mi_decl_noinline bool mi_bchunk_try_find_and_clear8(mi_bchunk_t* chunk, size_t* pidx) {
#if MI_OPT_SIMD && defined(__AVX2__) && (MI_BCHUNK_BITS==512)
while (true) {
// since a cache-line is 64b, load all at once
const __m256i vec1 = _mm256_load_si256((const __m256i*)chunk->bfields);
const __m256i vec2 = _mm256_load_si256((const __m256i*)chunk->bfields+1);
const __m256i cmpv = mi_mm256_ones();
const __m256i vcmp1 = _mm256_cmpeq_epi8(vec1, cmpv); // (byte == ~0 ? 0xFF : 0)
const __m256i vcmp2 = _mm256_cmpeq_epi8(vec2, cmpv); // (byte == ~0 ? 0xFF : 0)
const uint32_t mask1 = _mm256_movemask_epi8(vcmp1); // mask of most significant bit of each byte
const uint32_t mask2 = _mm256_movemask_epi8(vcmp2); // mask of most significant bit of each byte
const uint64_t mask = ((uint64_t)mask2 << 32) | mask1;
// mask is inverted, so each bit is 0xFF iff the corresponding byte has a bit set (and thus can be cleared)
if (mask==0) return false;
const size_t bidx = _tzcnt_u64(mask); // byte-idx of the byte in the chunk
const size_t chunk_idx = bidx / 8;
const size_t byte_idx = bidx % 8; // byte index of the byte in the bfield
mi_assert_internal(chunk_idx < MI_BCHUNK_FIELDS);
if mi_likely(mi_bfield_atomic_try_clear8(&chunk->bfields[chunk_idx], byte_idx, NULL)) { // clear it atomically
*pidx = (chunk_idx*MI_BFIELD_BITS) + 8*byte_idx;
mi_assert_internal(*pidx + 8 <= MI_BCHUNK_BITS);
return true;
}
// try again
}
#else
// first skip allset fields to reduce fragmentation
for(int i = 0; i < MI_BCHUNK_FIELDS; i++) {
if (mi_bchunk_try_find_and_clear8_at(chunk, i, pidx, false /* don't allow allset fields */)) return true;
}
for (int i = 0; i < MI_BCHUNK_FIELDS; i++) {
if (mi_bchunk_try_find_and_clear8_at(chunk, i, pidx, true /* allow allset fields */)) return true;
}
return false;
#endif
}
static inline bool mi_bchunk_try_find_and_clear_8(mi_bchunk_t* chunk, size_t n, size_t* pidx) {
mi_assert_internal(n==8); MI_UNUSED(n);
return mi_bchunk_try_find_and_clear8(chunk, pidx);
}
// find least bfield in a chunk with all bits set, and try unset it atomically
// set `*pidx` to its bit index (0 <= *pidx < MI_BCHUNK_BITS) on success.
// Used to find large size pages in the free blocks.
// todo: try neon version
static mi_decl_noinline bool mi_bchunk_try_find_and_clearX(mi_bchunk_t* chunk, size_t* pidx) {
#if MI_OPT_SIMD && defined(__AVX2__) && (MI_BCHUNK_BITS==512)
while (true) {
// since a cache-line is 64b, load all at once
const __m256i vec1 = _mm256_load_si256((const __m256i*)chunk->bfields);
const __m256i vec2 = _mm256_load_si256((const __m256i*)chunk->bfields+1);
const __m256i cmpv = mi_mm256_ones();
const __m256i vcmp1 = _mm256_cmpeq_epi64(vec1, cmpv); // (bfield == ~0 ? -1 : 0)
const __m256i vcmp2 = _mm256_cmpeq_epi64(vec2, cmpv); // (bfield == ~0 ? -1 : 0)
const uint32_t mask1 = _mm256_movemask_epi8(vcmp1); // mask of most significant bit of each byte
const uint32_t mask2 = _mm256_movemask_epi8(vcmp2); // mask of most significant bit of each byte
const uint64_t mask = ((uint64_t)mask2 << 32) | mask1;
// mask is inverted, so each 8-bits are set iff the corresponding elem64 has all bits set (and thus can be cleared)
if (mask==0) return false;
mi_assert_internal((_tzcnt_u64(mask)%8) == 0); // tzcnt == 0, 8, 16, 24 , ..
const size_t chunk_idx = _tzcnt_u64(mask) / 8;
mi_assert_internal(chunk_idx < MI_BCHUNK_FIELDS);
if mi_likely(mi_bfield_atomic_try_clearX(&chunk->bfields[chunk_idx])) {
*pidx = chunk_idx*MI_BFIELD_BITS;
mi_assert_internal(*pidx + MI_BFIELD_BITS <= MI_BCHUNK_BITS);
return true;
}
// try again
}
#else
for (int i = 0; i < MI_BCHUNK_FIELDS; i++) {
const mi_bfield_t b = mi_atomic_load_relaxed(&chunk->bfields[i]);
if (~b==0 && mi_bfield_atomic_try_clearX(&chunk->bfields[i])) {
*pidx = i*MI_BFIELD_BITS;
mi_assert_internal(*pidx + MI_BFIELD_BITS <= MI_BCHUNK_BITS);
return true;
}
}
return false;
#endif
}
static inline bool mi_bchunk_try_find_and_clear_X(mi_bchunk_t* chunk, size_t n, size_t* pidx) {
mi_assert_internal(n==MI_BFIELD_BITS); MI_UNUSED(n);
return mi_bchunk_try_find_and_clearX(chunk, pidx);
}
// find a sequence of `n` bits in a chunk with `n < MI_BFIELD_BITS` with all bits set,
// and try to clear them atomically.
// set `*pidx` to its bit index (0 <= *pidx <= MI_BCHUNK_BITS - n) on success.
// (We do not cross bfield boundaries)
static mi_decl_noinline bool mi_bchunk_try_find_and_clearNX(mi_bchunk_t* chunk, size_t n, size_t* pidx) {
if (n == 0 || n > MI_BFIELD_BITS) return false;
const mi_bfield_t mask = mi_bfield_mask(n, 0);
for(int i = 0; i < MI_BCHUNK_FIELDS; i++) {
mi_bfield_t b = mi_atomic_load_relaxed(&chunk->bfields[i]);
size_t bshift = 0;
size_t idx;
while (mi_bfield_find_least_bit(b, &idx)) { // find least 1-bit
b >>= idx;
bshift += idx;
if (bshift + n > MI_BFIELD_BITS) break;
if ((b&mask) == mask) { // found a match
mi_assert_internal( ((mask << bshift) >> bshift) == mask );
if mi_likely(mi_bfield_atomic_try_clear_mask(&chunk->bfields[i],mask<<bshift,NULL)) {
*pidx = (i*MI_BFIELD_BITS) + bshift;
mi_assert_internal(*pidx < MI_BCHUNK_BITS);
mi_assert_internal(*pidx + n <= MI_BCHUNK_BITS);
return true;
}
else {
// if failed to atomically commit, reload b and try again from this position
bshift -= idx;
b = mi_atomic_load_relaxed(&chunk->bfields[i]) >> bshift;
}
}
else {
// advance
const size_t ones = mi_bfield_ctz(~b); // skip all ones (since it didn't fit the mask)
mi_assert_internal(ones>0);
b >>= ones;
bshift += ones;
}
}
}
return false;
}
// find a sequence of `n` bits in a chunk with `n < MI_BCHUNK_BITS` with all bits set,
// and try to clear them atomically.
// set `*pidx` to its bit index (0 <= *pidx <= MI_BCHUNK_BITS - n) on success.
// This can cross bfield boundaries.
static mi_decl_noinline bool mi_bchunk_try_find_and_clearN_(mi_bchunk_t* chunk, size_t n, size_t* pidx) {
if (n == 0 || n > MI_BCHUNK_BITS) return false; // cannot be more than a chunk
// we align at a bfield, and scan `field_count` fields
// n >= MI_BFIELD_BITS; find a first field that is 0
const size_t field_count = _mi_divide_up(n, MI_BFIELD_BITS); // we need this many fields
for (size_t i = 0; i <= MI_BCHUNK_FIELDS - field_count; i++)
{
// first pre-scan for a range of fields that are all set (up to the last one)
bool allset = true;
size_t j = 0;
size_t m = n;
do {
mi_assert_internal(i + j < MI_BCHUNK_FIELDS);
mi_bfield_t b = mi_atomic_load_relaxed(&chunk->bfields[i+j]);
size_t idx;
if (mi_bfield_find_least_bit(~b,&idx)) {
if (m > idx) {
allset = false;
i += j; // no need to look again at the previous fields
break;
}
}
else {
// all bits in b were set
m -= MI_BFIELD_BITS; // note: can underflow
}
} while (++j < field_count);
// if all set, we can try to atomically clear them
if (allset) {
const size_t cidx = i*MI_BFIELD_BITS;
if (mi_bchunk_try_clearN(chunk, cidx, n, NULL)) {
// we cleared all atomically
*pidx = cidx;
mi_assert_internal(*pidx < MI_BCHUNK_BITS);
mi_assert_internal(*pidx + n <= MI_BCHUNK_BITS);
return true;
}
}
// continue
}
return false;
}
//static inline bool mi_bchunk_try_find_and_clearN(mi_bchunk_t* chunk, size_t n, size_t* pidx) {
// if (n==1) return mi_bchunk_try_find_and_clear(chunk, pidx); // small pages
// if (n==8) return mi_bchunk_try_find_and_clear8(chunk, pidx); // medium pages
// if (n==MI_BFIELD_BITS) return mi_bchunk_try_find_and_clearX(chunk, pidx); // large pages
// if (n == 0 || n > MI_BCHUNK_BITS) return false; // cannot be more than a chunk
// if (n < MI_BFIELD_BITS) return mi_bchunk_try_find_and_clearNX(chunk, n, pidx);
// return mi_bchunk_try_find_and_clearN_(chunk, n, pidx);
//}
// ------- mi_bchunk_clear_once_set ---------------------------------------
static inline void mi_bchunk_clear_once_set(mi_bchunk_t* chunk, size_t cidx) {
mi_assert_internal(cidx < MI_BCHUNK_BITS);
const size_t i = cidx / MI_BFIELD_BITS;
const size_t idx = cidx % MI_BFIELD_BITS;
mi_bfield_atomic_clear_once_set(&chunk->bfields[i], idx);
}
// ------- mi_bitmap_all_are_clear ---------------------------------------
// are all bits in a bitmap chunk clear? (this uses guaranteed atomic reads)
static inline bool mi_bchunk_all_are_clear(mi_bchunk_t* chunk) {
for(int i = 0; i < MI_BCHUNK_FIELDS; i++) {
if (mi_atomic_load_relaxed(&chunk->bfields[i]) != 0) return false;
}
return true;
}
// are all bits in a bitmap chunk clear?
static inline bool mi_bchunk_all_are_clear_relaxed(mi_bchunk_t* chunk) {
#if MI_OPT_SIMD && defined(__AVX2__) && (MI_BCHUNK_BITS==256)
const __m256i vec = _mm256_load_si256((const __m256i*)chunk->bfields);
return mi_mm256_is_zero(vec);
#elif MI_OPT_SIMD && defined(__AVX2__) && (MI_BCHUNK_BITS==512)
// a 64b cache-line contains the entire chunk anyway so load both at once
const __m256i vec1 = _mm256_load_si256((const __m256i*)chunk->bfields);
const __m256i vec2 = _mm256_load_si256(((const __m256i*)chunk->bfields)+1);
return (mi_mm256_is_zero(_mm256_or_si256(vec1,vec2)));
#else
return mi_bchunk_all_are_clear(chunk);
#endif
}
static bool mi_bchunk_bsr(mi_bchunk_t* chunk, size_t* pidx) {
for (size_t i = MI_BCHUNK_FIELDS; i > 0; ) {
i--;
mi_bfield_t b = mi_atomic_load_relaxed(&chunk->bfields[i]);
size_t idx;
if (mi_bsr(b, &idx)) {
*pidx = (i*MI_BFIELD_BITS) + idx;
return true;
}
}
return false;
}
/* --------------------------------------------------------------------------------
bitmap chunkmap
-------------------------------------------------------------------------------- */
static void mi_bitmap_chunkmap_set_max(mi_bitmap_t* bitmap, size_t chunk_idx) {
size_t oldmax = mi_atomic_load_relaxed(&bitmap->chunk_max_accessed);
if mi_unlikely(chunk_idx > oldmax) {
mi_atomic_cas_strong_relaxed(&bitmap->chunk_max_accessed, &oldmax, chunk_idx);
}
}
static void mi_bitmap_chunkmap_set(mi_bitmap_t* bitmap, size_t chunk_idx) {
mi_assert(chunk_idx < mi_bitmap_chunk_count(bitmap));
mi_bchunk_set(&bitmap->chunkmap, chunk_idx);
mi_bitmap_chunkmap_set_max(bitmap, chunk_idx);
}
static bool mi_bitmap_chunkmap_try_clear(mi_bitmap_t* bitmap, size_t chunk_idx) {
mi_assert(chunk_idx < mi_bitmap_chunk_count(bitmap));
// check if the corresponding chunk is all clear
if (!mi_bchunk_all_are_clear_relaxed(&bitmap->chunks[chunk_idx])) return false;
// clear the chunkmap bit
mi_bchunk_clear(&bitmap->chunkmap, chunk_idx, NULL);
// .. but a concurrent set may have happened in between our all-clear test and the clearing of the
// bit in the mask. We check again to catch this situation.
if (!mi_bchunk_all_are_clear_relaxed(&bitmap->chunks[chunk_idx])) {
mi_bchunk_set(&bitmap->chunkmap, chunk_idx);
return false;
}
mi_bitmap_chunkmap_set_max(bitmap, chunk_idx);
return true;
}
/* --------------------------------------------------------------------------------
bitmap
-------------------------------------------------------------------------------- */
size_t mi_bitmap_size(size_t bit_count, size_t* pchunk_count) {
mi_assert_internal((bit_count % MI_BCHUNK_BITS) == 0);
bit_count = _mi_align_up(bit_count, MI_BCHUNK_BITS);
mi_assert_internal(bit_count <= MI_BITMAP_MAX_BIT_COUNT);
mi_assert_internal(bit_count > 0);
const size_t chunk_count = bit_count / MI_BCHUNK_BITS;
mi_assert_internal(chunk_count >= 1);
const size_t size = offsetof(mi_bitmap_t,chunks) + (chunk_count * MI_BCHUNK_SIZE);
mi_assert_internal( (size%MI_BCHUNK_SIZE) == 0 );
if (pchunk_count != NULL) { *pchunk_count = chunk_count; }
return size;
}
// initialize a bitmap to all unset; avoid a mem_zero if `already_zero` is true
// returns the size of the bitmap
size_t mi_bitmap_init(mi_bitmap_t* bitmap, size_t bit_count, bool already_zero) {
size_t chunk_count;
const size_t size = mi_bitmap_size(bit_count, &chunk_count);
if (!already_zero) {
_mi_memzero_aligned(bitmap, size);
}
mi_atomic_store_release(&bitmap->chunk_count, chunk_count);
mi_assert_internal(mi_atomic_load_relaxed(&bitmap->chunk_count) <= MI_BITMAP_MAX_CHUNK_COUNT);
return size;
}
// Set a sequence of `n` bits in the bitmap (and can cross chunks). Not atomic so only use if local to a thread.
void mi_bitmap_unsafe_setN(mi_bitmap_t* bitmap, size_t idx, size_t n) {
mi_assert_internal(n>0);
mi_assert_internal(idx + n <= mi_bitmap_max_bits(bitmap));
// first chunk
size_t chunk_idx = idx / MI_BCHUNK_BITS;
const size_t cidx = idx % MI_BCHUNK_BITS;
size_t m = MI_BCHUNK_BITS - cidx;
if (m > n) { m = n; }
mi_bchunk_setN(&bitmap->chunks[chunk_idx], cidx, m, NULL);
mi_bitmap_chunkmap_set(bitmap, chunk_idx);
// n can be large so use memset for efficiency for all in-between chunks
chunk_idx++;
n -= m;
const size_t mid_chunks = n / MI_BCHUNK_BITS;
if (mid_chunks > 0) {
_mi_memset(&bitmap->chunks[chunk_idx], ~0, mid_chunks * MI_BCHUNK_SIZE);
const size_t end_chunk = chunk_idx + mid_chunks;
while (chunk_idx < end_chunk) {
if ((chunk_idx % MI_BFIELD_BITS) == 0 && (chunk_idx + MI_BFIELD_BITS <= end_chunk)) {
// optimize: we can set a full bfield in the chunkmap
mi_atomic_store_relaxed( &bitmap->chunkmap.bfields[chunk_idx/MI_BFIELD_BITS], mi_bfield_all_set());
mi_bitmap_chunkmap_set(bitmap, chunk_idx + MI_BFIELD_BITS - 1); // track the max set
chunk_idx += MI_BFIELD_BITS;
}
else {
mi_bitmap_chunkmap_set(bitmap, chunk_idx);
chunk_idx++;
}
}
n -= (mid_chunks * MI_BCHUNK_BITS);
}
// last chunk
if (n > 0) {
mi_assert_internal(n < MI_BCHUNK_BITS);
mi_assert_internal(chunk_idx < MI_BCHUNK_FIELDS);
mi_bchunk_setN(&bitmap->chunks[chunk_idx], 0, n, NULL);
mi_bitmap_chunkmap_set(bitmap, chunk_idx);
}
// reset max_accessed
mi_atomic_store_relaxed(&bitmap->chunk_max_accessed, 0);
}
// ------- mi_bitmap_xset ---------------------------------------
// Set/clear a bit in the bitmap; returns `true` if atomically transitioned from 0 to 1 (or 1 to 0)
bool mi_bitmap_xset(mi_xset_t set, mi_bitmap_t* bitmap, size_t idx) {
mi_assert_internal(idx < mi_bitmap_max_bits(bitmap));
const size_t chunk_idx = idx / MI_BCHUNK_BITS;
const size_t cidx = idx % MI_BCHUNK_BITS;
mi_assert_internal(chunk_idx < mi_bitmap_chunk_count(bitmap));
if (set) {
const bool wasclear = mi_bchunk_set(&bitmap->chunks[chunk_idx], cidx);
mi_bitmap_chunkmap_set(bitmap, chunk_idx); // set afterwards
return wasclear;
}
else {
bool maybe_all_clear;
const bool wasset = mi_bchunk_clear(&bitmap->chunks[chunk_idx], cidx, &maybe_all_clear);
if (maybe_all_clear) { mi_bitmap_chunkmap_try_clear(bitmap, chunk_idx); }
return wasset;
}
}
// Set/clear aligned 8-bits in the bitmap (with `(idx%8)==0`).
// Returns `true` if atomically transitioned from 0 to 1 (or 1 to 0)
static bool mi_bitmap_xset8(mi_xset_t set, mi_bitmap_t* bitmap, size_t idx) {
mi_assert_internal(idx < mi_bitmap_max_bits(bitmap));
mi_assert_internal((idx%8)==0);
const size_t chunk_idx = idx / MI_BCHUNK_BITS;
const size_t byte_idx = (idx % MI_BCHUNK_BITS)/8;
mi_assert_internal(chunk_idx < mi_bitmap_chunk_count(bitmap));
if (set) {
const bool wasclear = mi_bchunk_set8(&bitmap->chunks[chunk_idx], byte_idx);
mi_bitmap_chunkmap_set(bitmap, chunk_idx); // set afterwards
return wasclear;
}
else {
bool maybe_all_clear;
const bool wasset = mi_bchunk_clear8(&bitmap->chunks[chunk_idx], byte_idx, &maybe_all_clear);
if (maybe_all_clear) { mi_bitmap_chunkmap_try_clear(bitmap, chunk_idx); }
return wasset;
}
}
// Set/clear a field of bits.
// Returns `true` if atomically transitioned from 0 to ~0 (or ~0 to 0)
static bool mi_bitmap_xsetX(mi_xset_t set, mi_bitmap_t* bitmap, size_t idx) {
mi_assert_internal(idx < mi_bitmap_max_bits(bitmap));
mi_assert_internal((idx%MI_BFIELD_BITS)==0);
const size_t chunk_idx = idx / MI_BCHUNK_BITS;
const size_t field_idx = (idx % MI_BCHUNK_BITS)/MI_BFIELD_BITS;
mi_assert_internal(chunk_idx < mi_bitmap_chunk_count(bitmap));
if (set) {
const bool wasclear = mi_bchunk_setX(&bitmap->chunks[chunk_idx],field_idx);
mi_bitmap_chunkmap_set(bitmap, chunk_idx); // set afterwards
return wasclear;
}
else {
bool maybe_all_clear;
const bool wasset = mi_bchunk_clearX(&bitmap->chunks[chunk_idx], field_idx, &maybe_all_clear);
if (maybe_all_clear) { mi_bitmap_chunkmap_try_clear(bitmap, chunk_idx); }
return wasset;
}
}
// Set/clear a sequence of `n` bits in the bitmap; returns `true` if atomically transitioned from 0's to 1's (or 1's to 0's).
// `n` cannot cross chunk boundaries (and `n <= MI_BCHUNK_BITS`)!
static bool mi_bitmap_xsetN_(mi_xset_t set, mi_bitmap_t* bitmap, size_t idx, size_t n, size_t* already_xset ) {
mi_assert_internal(n>0);
mi_assert_internal(n<=MI_BCHUNK_BITS);
const size_t chunk_idx = idx / MI_BCHUNK_BITS;
const size_t cidx = idx % MI_BCHUNK_BITS;
mi_assert_internal(cidx + n <= MI_BCHUNK_BITS); // don't cross chunks (for now)
mi_assert_internal(chunk_idx < mi_bitmap_chunk_count(bitmap));
if (cidx + n > MI_BCHUNK_BITS) { n = MI_BCHUNK_BITS - cidx; } // paranoia
if (set) {
const bool allclear = mi_bchunk_setN(&bitmap->chunks[chunk_idx], cidx, n, already_xset);
mi_bitmap_chunkmap_set(bitmap,chunk_idx); // set afterwards
return allclear;
}
else {
size_t already_clear = 0;
const bool allset = mi_bchunk_clearN(&bitmap->chunks[chunk_idx], cidx, n, &already_clear );
if (already_xset != NULL) { *already_xset = already_clear; }
if (already_clear < n) { mi_bitmap_chunkmap_try_clear(bitmap, chunk_idx); }
return allset;
}
}
// Set/clear a sequence of `n` bits in the bitmap; returns `true` if atomically transitioned from 0's to 1's (or 1's to 0's).
// `n` cannot cross chunk boundaries (and `n <= MI_BCHUNK_BITS`)!
bool mi_bitmap_xsetN(mi_xset_t set, mi_bitmap_t* bitmap, size_t idx, size_t n, size_t* already_xset) {
mi_assert_internal(n>0 && n<=MI_BCHUNK_BITS);
if (n==1) return mi_bitmap_xset(set, bitmap, idx);
if (n==8) return mi_bitmap_xset8(set, bitmap, idx);
if (n==MI_BFIELD_BITS) return mi_bitmap_xsetX(set, bitmap, idx);
return mi_bitmap_xsetN_(set, bitmap, idx, n, already_xset);
}
// ------- mi_bitmap_is_xset ---------------------------------------
// Is a sequence of n bits already all set/cleared?
bool mi_bitmap_is_xsetN(mi_xset_t set, mi_bitmap_t* bitmap, size_t idx, size_t n) {
mi_assert_internal(n>0);
mi_assert_internal(n<=MI_BCHUNK_BITS);
mi_assert_internal(idx + n <= mi_bitmap_max_bits(bitmap));
const size_t chunk_idx = idx / MI_BCHUNK_BITS;
const size_t cidx = idx % MI_BCHUNK_BITS;
mi_assert_internal(cidx + n <= MI_BCHUNK_BITS); // don't cross chunks (for now)
mi_assert_internal(chunk_idx < mi_bitmap_chunk_count(bitmap));
if (cidx + n > MI_BCHUNK_BITS) { n = MI_BCHUNK_BITS - cidx; } // paranoia
return mi_bchunk_is_xsetN(set, &bitmap->chunks[chunk_idx], cidx, n);
}
/* --------------------------------------------------------------------------------
Iterate through a bfield
-------------------------------------------------------------------------------- */
// Cycle iteration through a bitfield. This is used to space out threads
// so there is less chance of contention. When searching for a free page we
// like to first search only the accessed part (so we reuse better). This
// high point is called the `cycle`.
//
// We then iterate through the bitfield as:
// first: [start, cycle>
// then : [0, start>
// then : [cycle, MI_BFIELD_BITS>
//
// The start is determined usually as `tseq % cycle` to have each thread
// start at a different spot.
// - We use `popcount` to improve branch prediction (maybe not needed? can we simplify?)
// - The `cycle_mask` is the part `[start, cycle>`.
#define mi_bfield_iterate(bfield,start,cycle,name_idx,SUF) { \
mi_assert_internal(start <= cycle); \
mi_assert_internal(start < MI_BFIELD_BITS); \
mi_assert_internal(cycle < MI_BFIELD_BITS); \
mi_bfield_t _cycle_mask##SUF = mi_bfield_mask(cycle - start, start); \
size_t _bcount##SUF = mi_bfield_popcount(bfield); \
mi_bfield_t _b##SUF = bfield & _cycle_mask##SUF; /* process [start, cycle> first*/\
while(_bcount##SUF > 0) { \
_bcount##SUF--;\
if (_b##SUF==0) { _b##SUF = bfield & ~_cycle_mask##SUF; } /* process [0,start> + [cycle, MI_BFIELD_BITS> next */ \
size_t name_idx; \
bool _found##SUF = mi_bfield_find_least_bit(_b##SUF,&name_idx); \
mi_assert_internal(_found##SUF); MI_UNUSED(_found##SUF); \
{ \
#define mi_bfield_iterate_end(SUF) \
} \
_b##SUF = mi_bfield_clear_least_bit(_b##SUF); \
} \
}
#define mi_bfield_cycle_iterate(bfield,tseq,cycle,name_idx,SUF) { \
const size_t _start##SUF = (uint32_t)(tseq) % (uint32_t)(cycle); /* or: 0 to always search from the start? */\
mi_bfield_iterate(bfield,_start##SUF,cycle,name_idx,SUF)
#define mi_bfield_cycle_iterate_end(SUF) \
mi_bfield_iterate_end(SUF); }
/* --------------------------------------------------------------------------------
mi_bitmap_find
(used to find free pages)
-------------------------------------------------------------------------------- */
typedef bool (mi_bitmap_visit_fun_t)(mi_bitmap_t* bitmap, size_t chunk_idx, size_t n, size_t* idx, void* arg1, void* arg2);
// Go through the bitmap and for every sequence of `n` set bits, call the visitor function.
// If it returns `true` stop the search.
static inline bool mi_bitmap_find(mi_bitmap_t* bitmap, size_t tseq, size_t n, size_t* pidx, mi_bitmap_visit_fun_t* on_find, void* arg1, void* arg2)
{
// we space out threads to reduce contention
const size_t cmap_max_count = _mi_divide_up(mi_bitmap_chunk_count(bitmap),MI_BFIELD_BITS);
const size_t chunk_acc = mi_atomic_load_relaxed(&bitmap->chunk_max_accessed);
const size_t cmap_acc = chunk_acc / MI_BFIELD_BITS;
const size_t cmap_acc_bits = 1 + (chunk_acc % MI_BFIELD_BITS);
// create a mask over the chunkmap entries to iterate over them efficiently
mi_assert_internal(MI_BFIELD_BITS >= MI_BCHUNK_FIELDS);
const mi_bfield_t cmap_mask = mi_bfield_mask(cmap_max_count,0);
const size_t cmap_cycle = cmap_acc+1;
mi_bfield_cycle_iterate(cmap_mask, tseq, cmap_cycle, cmap_idx, X)
{
// and for each chunkmap entry we iterate over its bits to find the chunks
mi_bfield_t cmap_entry = mi_atomic_load_relaxed(&bitmap->chunkmap.bfields[cmap_idx]);
size_t cmap_entry_cycle = (cmap_idx != cmap_acc ? MI_BFIELD_BITS : cmap_acc_bits);
mi_bfield_cycle_iterate(cmap_entry, tseq, cmap_entry_cycle, eidx, Y)
{
mi_assert_internal(eidx <= MI_BFIELD_BITS);
const size_t chunk_idx = cmap_idx*MI_BFIELD_BITS + eidx;
mi_assert_internal(chunk_idx < mi_bitmap_chunk_count(bitmap));
if ((*on_find)(bitmap, chunk_idx, n, pidx, arg1, arg2)) {
return true;
}
}
mi_bfield_cycle_iterate_end(Y);
}
mi_bfield_cycle_iterate_end(X);
return false;
}
/* --------------------------------------------------------------------------------
mi_bitmap_try_find_and_clear -- used to find free pages
note: the compiler will fully inline the indirect function calls
-------------------------------------------------------------------------------- */
typedef bool (mi_bchunk_try_find_and_clear_fun_t)(mi_bchunk_t* chunk, size_t n, size_t* idx);
static bool mi_bitmap_try_find_and_clear_visit(mi_bitmap_t* bitmap, size_t chunk_idx, size_t n, size_t* pidx, void* arg1, void* arg2) {
MI_UNUSED(arg2);
mi_bchunk_try_find_and_clear_fun_t* try_find_and_clear = (mi_bchunk_try_find_and_clear_fun_t*)arg1;
size_t cidx;
// if we find a spot in the chunk we are done
if ((*try_find_and_clear)(&bitmap->chunks[chunk_idx], n, &cidx)) {
*pidx = (chunk_idx * MI_BCHUNK_BITS) + cidx;
mi_assert_internal(*pidx + n <= mi_bitmap_max_bits(bitmap));
return true;
}
else {
/* we may find that all are cleared only on a second iteration but that is ok as the chunkmap is a conservative approximation. */
mi_bitmap_chunkmap_try_clear(bitmap, chunk_idx);
return false;
}
}
static inline bool mi_bitmap_try_find_and_clear_generic(mi_bitmap_t* bitmap, size_t tseq, size_t n, size_t* pidx, mi_bchunk_try_find_and_clear_fun_t* try_find_and_clear) {
return mi_bitmap_find(bitmap, tseq, n, pidx, &mi_bitmap_try_find_and_clear_visit, (void*)try_find_and_clear, NULL);
}
mi_decl_nodiscard bool mi_bitmap_try_find_and_clear(mi_bitmap_t* bitmap, size_t tseq, size_t* pidx) {
return mi_bitmap_try_find_and_clear_generic(bitmap, tseq, 1, pidx, &mi_bchunk_try_find_and_clear_1);
}
mi_decl_nodiscard bool mi_bitmap_try_find_and_clear8(mi_bitmap_t* bitmap, size_t tseq, size_t* pidx) {
return mi_bitmap_try_find_and_clear_generic(bitmap, tseq, 8, pidx, &mi_bchunk_try_find_and_clear_8);
}
mi_decl_nodiscard bool mi_bitmap_try_find_and_clearX(mi_bitmap_t* bitmap, size_t tseq, size_t* pidx) {
return mi_bitmap_try_find_and_clear_generic(bitmap, tseq, MI_BFIELD_BITS, pidx, &mi_bchunk_try_find_and_clear_X);
}
mi_decl_nodiscard bool mi_bitmap_try_find_and_clearNX(mi_bitmap_t* bitmap, size_t tseq, size_t n, size_t* pidx) {
mi_assert_internal(n<=MI_BFIELD_BITS);
return mi_bitmap_try_find_and_clear_generic(bitmap, tseq, n, pidx, &mi_bchunk_try_find_and_clearNX);
}
mi_decl_nodiscard bool mi_bitmap_try_find_and_clearN_(mi_bitmap_t* bitmap, size_t tseq, size_t n, size_t* pidx) {
mi_assert_internal(n<=MI_BCHUNK_BITS);
return mi_bitmap_try_find_and_clear_generic(bitmap, tseq, n, pidx, &mi_bchunk_try_find_and_clearN_);
}
/* --------------------------------------------------------------------------------
Bitmap: try_find_and_claim -- used to allocate abandoned pages
note: the compiler will fully inline the indirect function call
-------------------------------------------------------------------------------- */
typedef struct mi_claim_fun_data_s {
mi_arena_t* arena;
mi_subproc_t* subproc;
mi_heaptag_t heap_tag;
} mi_claim_fun_data_t;
static bool mi_bitmap_try_find_and_claim_visit(mi_bitmap_t* bitmap, size_t chunk_idx, size_t n, size_t* pidx, void* arg1, void* arg2)
{
mi_assert_internal(n==1); MI_UNUSED(n);
mi_claim_fun_t* claim_fun = (mi_claim_fun_t*)arg1;
mi_claim_fun_data_t* claim_data = (mi_claim_fun_data_t*)arg2;
size_t cidx;
if mi_likely(mi_bchunk_try_find_and_clear(&bitmap->chunks[chunk_idx], &cidx)) {
const size_t slice_index = (chunk_idx * MI_BCHUNK_BITS) + cidx;
mi_assert_internal(slice_index < mi_bitmap_max_bits(bitmap));
bool keep_set = true;
if ((*claim_fun)(slice_index, claim_data->arena, claim_data->subproc, claim_data->heap_tag, &keep_set)) {
// success!
mi_assert_internal(!keep_set);
*pidx = slice_index;
return true;
}
else {
// failed to claim it, set abandoned mapping again (unless the page was freed)
if (keep_set) {
const bool wasclear = mi_bchunk_set(&bitmap->chunks[chunk_idx], cidx);
mi_assert_internal(wasclear); MI_UNUSED(wasclear);
}
}
}
else {
// we may find that all are cleared only on a second iteration but that is ok as
// the chunkmap is a conservative approximation.
mi_bitmap_chunkmap_try_clear(bitmap, chunk_idx);
}
return false;
}
// Find a set bit in the bitmap and try to atomically clear it and claim it.
// (Used to find pages in the pages_abandoned bitmaps.)
mi_decl_nodiscard bool mi_bitmap_try_find_and_claim(mi_bitmap_t* bitmap, size_t tseq, size_t* pidx,
mi_claim_fun_t* claim, mi_arena_t* arena, mi_subproc_t* subproc, mi_heaptag_t heap_tag)
{
mi_claim_fun_data_t claim_data = { arena, subproc, heap_tag };
return mi_bitmap_find(bitmap, tseq, 1, pidx, &mi_bitmap_try_find_and_claim_visit, (void*)claim, &claim_data);
}
bool mi_bitmap_bsr(mi_bitmap_t* bitmap, size_t* idx) {
const size_t chunkmap_max = _mi_divide_up(mi_bitmap_chunk_count(bitmap), MI_BFIELD_BITS);
for (size_t i = chunkmap_max; i > 0; ) {
i--;
mi_bfield_t cmap = mi_atomic_load_relaxed(&bitmap->chunkmap.bfields[i]);
size_t cmap_idx;
if (mi_bsr(cmap,&cmap_idx)) {
// highest chunk
const size_t chunk_idx = i*MI_BFIELD_BITS + cmap_idx;
size_t cidx;
if (mi_bchunk_bsr(&bitmap->chunks[chunk_idx], &cidx)) {
*idx = (chunk_idx * MI_BCHUNK_BITS) + cidx;
return true;
}
}
}
return false;
}
// Clear a bit once it is set.
void mi_bitmap_clear_once_set(mi_bitmap_t* bitmap, size_t idx) {
mi_assert_internal(idx < mi_bitmap_max_bits(bitmap));
const size_t chunk_idx = idx / MI_BCHUNK_BITS;
const size_t cidx = idx % MI_BCHUNK_BITS;
mi_assert_internal(chunk_idx < mi_bitmap_chunk_count(bitmap));
mi_bchunk_clear_once_set(&bitmap->chunks[chunk_idx], cidx);
}
// Visit all set bits in a bitmap.
// todo: optimize further? maybe use avx512 to directly get all indices using a mask_compressstore?
bool _mi_bitmap_forall_set(mi_bitmap_t* bitmap, mi_forall_set_fun_t* visit, mi_arena_t* arena, void* arg) {
// for all chunkmap entries
const size_t chunkmap_max = _mi_divide_up(mi_bitmap_chunk_count(bitmap), MI_BFIELD_BITS);
for(size_t i = 0; i < chunkmap_max; i++) {
mi_bfield_t cmap_entry = mi_atomic_load_relaxed(&bitmap->chunkmap.bfields[i]);
size_t cmap_idx;
// for each chunk (corresponding to a set bit in a chunkmap entry)
while (mi_bfield_foreach_bit(&cmap_entry, &cmap_idx)) {
const size_t chunk_idx = i*MI_BFIELD_BITS + cmap_idx;
// for each chunk field
mi_bchunk_t* const chunk = &bitmap->chunks[chunk_idx];
for (size_t j = 0; j < MI_BCHUNK_FIELDS; j++) {
const size_t base_idx = (chunk_idx*MI_BCHUNK_BITS) + (j*MI_BFIELD_BITS);
mi_bfield_t b = mi_atomic_load_relaxed(&chunk->bfields[j]);
size_t bidx;
while (mi_bfield_foreach_bit(&b, &bidx)) {
const size_t idx = base_idx + bidx;
if (!visit(idx, arena, arg)) return false;
}
}
}
}
return true;
}
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