xo-alloc2: streamlining + bugfixes [wip]
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8d0af9a0e3
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6cf535eaef
11 changed files with 312 additions and 10 deletions
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@ -166,6 +166,9 @@ namespace xo {
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last_error_{}
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{
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//retval.checkpoint_ = lo_;
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/** make sure guard size is aligned **/
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config_.guard_z_ = padding::with_padding(config_.guard_z_);
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}
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DArena::DArena(DArena && other) {
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@ -145,23 +145,194 @@ namespace xo {
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std::byte *
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IAllocator_DArena::alloc(DArena & s,
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std::size_t req_z)
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{
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/* - primary allocation path:
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* exactly 1 header per alloc() call.
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* - store_header_flag follows configuration
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*/
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return _alloc(s, req_z,
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alloc_mode::standard);
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}
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std::byte *
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IAllocator_DArena::super_alloc(DArena & s,
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std::size_t req_z)
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{
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/* - (uncommon) pattern for parent alloc immediately followed by
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* zero-or-more susidiary allocs, all sharing a single header.
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* - collapses into alloc() behavior when
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* ArenaConfig.store_header_flag_ disabled
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*/
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bool remember_header_flag = s.config_.store_header_flag_;
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return _alloc(s, req_z,
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alloc_mode::super);
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}
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std::byte *
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IAllocator_DArena::sub_alloc(DArena & s,
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std::size_t req_z,
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bool complete_flag)
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{
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/* - (uncommon) pattern for subsidiary allocs:
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* that piggyback onto preceding super_alloc()
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* - collapses into alloc() behavior when
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* ArenaConfig.store_header_flag_ disabled
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*/
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return _alloc(s, req_z,
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(complete_flag
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? alloc_mode::sub_complete
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: alloc_mode::sub_incomplete));
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#ifdef OBSOLETE
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if ((req_z == 0) && complete_flag) [[unlikely]] {
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/** use zero req_z with complete_flag to clear s.last_header_ **/
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if (s.config_.store_header_flag_) {
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if (!s.last_header_) [[unlikely]] {
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++(s.error_count_);
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s.last_error_ = AllocatorError(error::orphan_sub_alloc,
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s.error_count_,
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0 /*add_commit_z*/, s.committed_z_, reserved(s));
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} else {
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s.last_header_ = nullptr;
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}
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}
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return nullptr;
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}
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byte * free0 = s.free_;
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byte * mem = _alloc(s, req_z,
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complete_flag ? alloc_mode::sub_complete : alloc_mode::sub,
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false /*!store_header_flag*/,
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false /*!remember_header_flag*/);
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if (!mem) [[unlikely]] {
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/* error already captured */
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return nullptr;
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}
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byte * free1 = s.free_;
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/* used: accounting for padding applied to req_z */
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size_t z0 = (free1 - free0);
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assert(z0 > 0);
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if (s.config_.store_header_flag_) {
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if (!s.last_header_) [[unlikely]] {
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++(s.error_count_);
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s.last_error_ = AllocatorError(error::orphan_sub_alloc,
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s.error_count_,
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0 /*add_commit_z*/, s.committed_z_, reserved(s));
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return nullptr;
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}
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/* s.last_header_ holds aggregate size of preceding super_alloc
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* (+ any sub-alloc's).
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*
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* Accumulate allocation size
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*/
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uint64_t header = *s.last_header_;
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if ((header & s.config_.header_size_mask_ & z0) != z0) [[unlikely]] {
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/* cumulative alloc size doesn't fit in configured header_size_mask bits */
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++(s.error_count_);
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s.last_error_ = AllocatorError(error::header_size_mask,
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s.error_count_,
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0 /*add_commit_z*/, s.committed_z_, reserved(s));
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return nullptr;
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}
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*s.last_header_ = ((header & ~s.config_.header_size_mask_) | z0);
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if (complete_flag) {
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s.last_header_ = nullptr;
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}
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}
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return mem;
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#endif
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}
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std::byte *
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IAllocator_DArena::_alloc(DArena & s,
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std::size_t req_z,
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bool store_header_flag,
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bool remember_header_flag)
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{
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scope log(XO_DEBUG(s.config_.debug_flag_));
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assert(padding::is_aligned((size_t)s.free_));
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/* remember_header_flag -implies-> store_header_flag */
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assert(store_header_flag || !remember_header_flag);
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/*
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* free_(pre)
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* v
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*
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* <-------------z1--------------->
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* < guard >< hz >< req_z >< dz >< guard >
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*
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* used <== +++++++++0000zzzz@@@@@@@@@@@@@@@@@ppppppp+++++++++ ==> unallocated
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*
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* ^ ^ ^
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* header mem |
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* ^ |
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* last_header_ free_(post)
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*
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* [+] guard after each allocation, for simple sanitize checks
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* [0] unused header bits (avail to application)
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* [z] record allocation size
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* [@] new allocated memory
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* [p] padding (to uintptr_t alignment)
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*/
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/* non-zero if header feature enabled */
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size_t hz = 0;
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/* dz: pad req_z to alignment size (multiple of 8 bytes, probably) */
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size_t dz = padding::alloc_padding(req_z);
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size_t z1 = req_z + dz;
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size_t z0 = req_z + dz;
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/* if non-zero: will store padded alloc size at the beginning of each allocation
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* reminder: important to store padded size for correct arena iteration
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*/
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uint64_t header = req_z + dz;
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if (store_header_flag) {
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if ((s.config_.header_size_mask_ & z0) == z0) [[likely]] {
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hz = sizeof(header);
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} else {
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/* req_z doesn't fit in configured header_size_mask bits */
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++(s.error_count_);
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s.last_error_ = AllocatorError(error::header_size_mask,
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s.error_count_,
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0 /*add_commit_z*/, s.committed_z_, reserved(s));
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return nullptr;
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}
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}
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size_t z1 = hz + z0;
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assert(padding::is_aligned(z1));
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if (expand(s, allocated(s) + z1)) [[likely]] {
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byte * mem = s.free_;
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if (store_header_flag) {
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(*(uint64_t *)s.free_) = header;
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if (remember_header_flag) {
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s.last_header_ = (uint64_t *)s.free_;
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}
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}
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byte * mem = s.free_ + hz;
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s.free_ += z1;
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log && log(xtag("self", s.config_.name_),
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xtag("hz", hz),
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xtag("z0", req_z),
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xtag("+pad", dz),
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xtag("z1", z1),
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