diff --git a/src/arena.c b/src/arena.c index 8362a31f..8b9ab4da 100644 --- a/src/arena.c +++ b/src/arena.c @@ -202,20 +202,7 @@ static mi_decl_noinline void* mi_arena_try_alloc_at( // set the dirty bits if (arena->memid.initially_zero) { - // size_t dirty_count = 0; - memid->initially_zero = mi_bitmap_setN(arena->slices_dirty, slice_index, slice_count, NULL); - //if (dirty_count>0) { - // if (memid->initially_zero) { - // _mi_error_message(EFAULT, "ouch1\n"); - // } - // // memid->initially_zero = false; - //} - //else { - // if (!memid->initially_zero) { - // _mi_error_message(EFAULT, "ouch2\n"); - // } - // // memid->initially_zero = true; - //} + memid->initially_zero = mi_bitmap_setN(arena->slices_dirty, slice_index, slice_count, NULL); } // set commit state @@ -235,7 +222,7 @@ static mi_decl_noinline void* mi_arena_try_alloc_at( #if MI_DEBUG > 1 if (memid->initially_zero) { if (!mi_mem_is_zero(p, mi_size_of_slices(slice_count))) { - _mi_error_message(EFAULT, "arena allocation was not zero-initialized!\n"); + _mi_error_message(EFAULT, "interal error: arena allocation was not zero-initialized!\n"); memid->initially_zero = false; } } @@ -327,31 +314,47 @@ static inline bool mi_arena_is_suitable(mi_arena_t* arena, mi_arena_id_t req_are return true; } -#define MI_THREADS_PER_ARENA (16) -#define mi_forall_arenas(req_arena_id, allow_large, tseq, var_arena_id, var_arena) \ +#define mi_forall_arenas(req_arena_id, tseq, name_arena) \ { \ - size_t _max_arena; \ - size_t _start; \ - if (req_arena_id == _mi_arena_id_none()) { \ - _max_arena = mi_atomic_load_relaxed(&mi_arena_count); \ - _start = (_max_arena <= 2 ? 0 : (tseq % (_max_arena-1))); \ - } \ - else { \ - _max_arena = 1; \ - _start = mi_arena_id_index(req_arena_id); \ - mi_assert_internal(mi_atomic_load_relaxed(&mi_arena_count) > _start); \ - } \ - for (size_t i = 0; i < _max_arena; i++) { \ - size_t _idx = i + _start; \ - if (_idx >= _max_arena) { _idx -= _max_arena; } \ - const mi_arena_id_t var_arena_id = mi_arena_id_create(_idx); MI_UNUSED(var_arena_id);\ - mi_arena_t* const var_arena = mi_arena_from_index(_idx); \ - if (var_arena != NULL && mi_arena_is_suitable(var_arena,req_arena_id,-1 /* todo: numa node */,allow_large)) \ - { + const size_t _arena_count = mi_atomic_load_relaxed(&mi_arena_count); \ + if (_arena_count > 0) { \ + const size_t _arena_cycle = _arena_count - 1; /* first search the arenas below the last one */ \ + size_t _start; \ + if (req_arena_id == _mi_arena_id_none()) { \ + /* always start searching in an arena 1 below the max */ \ + _start = (_arena_cycle <= 1 ? 0 : (tseq % _arena_cycle)); \ + } \ + else { \ + _start = mi_arena_id_index(req_arena_id); \ + mi_assert_internal(_start < _arena_count); \ + } \ + for (size_t _i = 0; _i < _arena_count; _i++) { \ + size_t _idx; \ + if (_i < _arena_cycle) { \ + _idx = _i + _start; \ + if (_idx >= _arena_cycle) { _idx -= _arena_cycle; } /* adjust so we rotate */ \ + } \ + else { \ + _idx = _i; \ + } \ + mi_arena_t* const name_arena = mi_arena_from_index(_idx); \ + if (name_arena != NULL) \ + { -#define mi_forall_arenas_end() }}} +#define mi_forall_arenas_end() \ + } \ + if (req_arena_id != _mi_arena_id_none()) break; \ + } \ + }} +#define mi_forall_suitable_arenas(req_arena_id, tseq, allow_large, name_arena) \ + mi_forall_arenas(req_arena_id,tseq,name_arena) { \ + if (mi_arena_is_suitable(name_arena, req_arena_id, -1 /* todo: numa node */, allow_large)) { \ + +#define mi_forall_suitable_arenas_end() \ + }} \ + mi_forall_arenas_end() /* ----------------------------------------------------------- Arena allocation @@ -369,12 +372,12 @@ static mi_decl_noinline void* mi_arena_try_find_free( // search arena's const size_t tseq = tld->tseq; - mi_forall_arenas(req_arena_id, allow_large, tseq, arena_id, arena) + mi_forall_suitable_arenas(req_arena_id, tseq, allow_large, arena) { void* p = mi_arena_try_alloc_at(arena, slice_count, commit, tseq, memid); if (p != NULL) return p; } - mi_forall_arenas_end(); + mi_forall_suitable_arenas_end(); return NULL; } @@ -517,7 +520,7 @@ static mi_page_t* mi_arena_page_try_find_abandoned(size_t slice_count, size_t bl // search arena's const bool allow_large = true; size_t tseq = tld->tseq; - mi_forall_arenas(req_arena_id, allow_large, tseq, arena_id, arena) + mi_forall_suitable_arenas(req_arena_id, tseq, allow_large, arena) { size_t slice_index; mi_bitmap_t* const bitmap = arena->pages_abandoned[bin]; @@ -545,7 +548,7 @@ static mi_page_t* mi_arena_page_try_find_abandoned(size_t slice_count, size_t bl return page; } } - mi_forall_arenas_end(); + mi_forall_suitable_arenas_end(); return NULL; } diff --git a/src/bitmap.c b/src/bitmap.c index 7f4c8776..fb8468fa 100644 --- a/src/bitmap.c +++ b/src/bitmap.c @@ -42,9 +42,9 @@ 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_zero(void) { + return 0; +} static inline mi_bfield_t mi_bfield_one(void) { return 1; @@ -64,9 +64,9 @@ static inline mi_bfield_t mi_bfield_mask(size_t bit_count, size_t shiftl) { // Find the least significant bit that can be xset (0 for MI_BIT_SET, 1 for MI_BIT_CLEAR). // return false if `x==~0` (for MI_BIT_SET) or `x==0` for MI_BIT_CLEAR (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_to_xset(mi_xset_t set, mi_bfield_t x, size_t* idx) { - return mi_bfield_find_least_bit((set ? ~x : x), idx); -} +//static inline bool mi_bfield_find_least_to_xset(mi_xset_t set, mi_bfield_t x, size_t* idx) { +// return mi_bfield_find_least_bit((set ? ~x : x), idx); +//} // 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) { @@ -244,10 +244,10 @@ static inline bool mi_bfield_atomic_try_clear8(_Atomic(mi_bfield_t)*b, size_t by // 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_weak_acq_rel(b, &old, mi_bfield_zero()); -//} +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()); +} // Check if all bits corresponding to a mask are set. @@ -514,31 +514,33 @@ static inline __m256i mi_mm256_zero(void) { 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_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 -// find least 0/1-bit in a chunk and try to set/clear it atomically +// 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_find_and_try_xset(mi_xset_t set, mi_bchunk_t* chunk, size_t* pidx) { -#if defined(__AVX2__) && (MI_BCHUNK_BITS==256) +static inline bool mi_bchunk_find_and_try_clear(mi_bchunk_t* chunk, size_t* pidx) { + #if 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, (set ? mi_mm256_ones() : mi_mm256_zero())); // (elem64 == ~0 / 0 ? 0xFF : 0) + 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 zero / one bit (and thus can be set/cleared) + // 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; 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 (mi_bfield_find_least_to_xset(set, chunk->bfields[chunk_idx], &cidx)) { // find the bit-idx that is set/clear - if mi_likely(mi_bfield_atomic_try_xset(set, &chunk->bfields[chunk_idx], cidx)) { // set/clear it atomically + 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; @@ -546,39 +548,42 @@ static inline bool mi_bchunk_find_and_try_xset(mi_xset_t set, mi_bchunk_t* chunk } // try again } -#elif defined(__AVX2__) && (MI_BCHUNK_BITS==512) + #elif defined(__AVX2__) && (MI_BCHUNK_BITS==512) while (true) { size_t chunk_idx = 0; - #if 1 + #if 0 + // one vector at a time __m256i vec = _mm256_load_si256((const __m256i*)chunk->bfields); - if ((set ? mi_mm256_is_ones(vec) : mi_mm256_is_zero(vec))) { + 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, (set ? mi_mm256_ones() : mi_mm256_zero())); // (elem64 == ~0 / 0 ? 0xFF : 0) + 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 zero / one bit (and thus can be set/cleared) + // 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 = (set ? mi_mm256_ones() : mi_mm256_zero()); - const __m256i vcmp1 = _mm256_cmpeq_epi64(vec1, cmpv); // (elem64 == ~0 / 0 ? 0xFF : 0) - const __m256i vcmp2 = _mm256_cmpeq_epi64(vec2, cmpv); // (elem64 == ~0 / 0 ? 0xFF : 0) + 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(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 zero / one bit (and thus can be set/cleared) + // 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 , .. - const size_t chunk_idx = _tzcnt_u64(mask) / 8; + chunk_idx = _tzcnt_u64(mask) / 8; #endif 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 (mi_bfield_find_least_to_xset(set, chunk->bfields[chunk_idx], &cidx)) { // find the bit-idx that is set/clear - if mi_likely(mi_bfield_atomic_try_xset(set, &chunk->bfields[chunk_idx], cidx)) { // set/clear it atomically + if (mi_bfield_find_least_bit(b, &cidx)) { // find the bit-idx that is clear + 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; @@ -586,11 +591,12 @@ static inline bool mi_bchunk_find_and_try_xset(mi_xset_t set, mi_bchunk_t* chunk } // try again } -#else + #else for (int i = 0; i < MI_BCHUNK_FIELDS; i++) { + const mi_bfield_t b = mi_atomic_load_relaxed(&chunk->bfields[i]); size_t idx; - if mi_unlikely(mi_bfield_find_least_to_xset(set, chunk->bfields[i], &idx)) { // find least 0-bit - if mi_likely(mi_bfield_atomic_try_xset(set, &chunk->bfields[i], idx)) { // try to set it atomically + if (mi_bfield_find_least_bit(b, &idx)) { // find least 1-bit + if mi_likely(mi_bfield_atomic_try_clear(&chunk->bfields[i], idx, NULL)) { // try to clear it atomically *pidx = (i*MI_BFIELD_BITS + idx); mi_assert_internal(*pidx < MI_BCHUNK_BITS); return true; @@ -598,48 +604,49 @@ static inline bool mi_bchunk_find_and_try_xset(mi_xset_t set, mi_bchunk_t* chunk } } return false; -#endif + #endif } -static inline bool mi_bchunk_find_and_try_clear(mi_bchunk_t* chunk, size_t* pidx) { - return mi_bchunk_find_and_try_xset(MI_BIT_CLEAR, chunk, pidx); -} - -//static inline bool mi_bchunk_find_and_try_set(mi_bchunk_t* chunk, size_t* pidx) { -// return mi_bchunk_find_and_try_xset(MI_BIT_SET, chunk, pidx); -//} // 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 inline bool mi_bchunk_find_and_try_clear8(mi_bchunk_t* chunk, size_t* pidx) { - #if defined(__AVX2__) && (MI_BCHUNK_BITS==256) - while(true) { - const __m256i vec = _mm256_load_si256((const __m256i*)chunk->bfields); - const __m256i vcmp = _mm256_cmpeq_epi8(vec, mi_mm256_ones()); // (byte == ~0 ? -1 : 0) - const uint32_t mask = _mm256_movemask_epi8(vcmp); // mask of most significant bit of each byte - if (mask == 0) return false; - const size_t i = _tzcnt_u32(mask); - mi_assert_internal(8*i < MI_BCHUNK_BITS); - const size_t chunk_idx = i / MI_BFIELD_SIZE; - const size_t byte_idx = i % MI_BFIELD_SIZE; - if mi_likely(mi_bfield_atomic_try_xset8(MI_BIT_CLEAR,&chunk->bfields[chunk_idx],byte_idx)) { // try to unset atomically - *pidx = (chunk_idx*MI_BFIELD_BITS) + (byte_idx*8); - mi_assert_internal(*pidx < MI_BCHUNK_BITS); + #if 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 for(int i = 0; i < MI_BCHUNK_FIELDS; i++) { - const mi_bfield_t x = chunk->bfields[i]; + const mi_bfield_t x = mi_atomic_load_relaxed(&chunk->bfields[i]); // has_set8 has low bit in each byte set if the byte in x == 0xFF const mi_bfield_t has_set8 = ((~x - MI_BFIELD_LO_BIT8) & // high bit set if byte in x is 0xFF or < 0x7F (x & 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_unlikely(mi_bfield_find_least_bit(has_set8,&idx)) { // find least 1-bit + 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; @@ -656,14 +663,58 @@ static inline bool mi_bchunk_find_and_try_clear8(mi_bchunk_t* chunk, size_t* pid } + +// 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 inline bool mi_bchunk_find_and_try_clearX(mi_bchunk_t* chunk, size_t* pidx) { +#if 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 +} + + // 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 bool mi_bchunk_find_and_try_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 = chunk->bfields[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 @@ -680,8 +731,9 @@ static bool mi_bchunk_find_and_try_clearNX(mi_bchunk_t* chunk, size_t n, size_t* return true; } else { - // if failed to atomically commit, try again from this position - b = (chunk->bfields[i] >> bshift); + // 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 { @@ -699,11 +751,11 @@ static bool mi_bchunk_find_and_try_clearNX(mi_bchunk_t* chunk, size_t n, size_t* // 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 bool mi_bchunk_find_and_try_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 - // if (n < MI_BFIELD_BITS) return mi_bchunk_find_and_try_clearNX(chunk, n, pidx); - - // we align an a field, and require `field_count` fields to be all clear. + + // 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++) @@ -740,14 +792,16 @@ static bool mi_bchunk_find_and_try_clearN_(mi_bchunk_t* chunk, size_t n, size_t* return true; } } + // continue } return false; } static inline bool mi_bchunk_find_and_try_clearN(mi_bchunk_t* chunk, size_t n, size_t* pidx) { - if (n==1) return mi_bchunk_find_and_try_clear(chunk, pidx); - if (n==8) return mi_bchunk_find_and_try_clear8(chunk, pidx); + if (n==1) return mi_bchunk_find_and_try_clear(chunk, pidx); // small pages + if (n==8) return mi_bchunk_find_and_try_clear8(chunk, pidx); // medium pages + if (n==MI_BFIELD_BITS) return mi_bchunk_find_and_try_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_find_and_try_clearNX(chunk, n, pidx); return mi_bchunk_find_and_try_clearN_(chunk, n, pidx);