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xo-alloc2: streamlining + bugfixes [wip]

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This commit is contained in:
Roland Conybeare 2025-12-12 19:44:38 -05:00
commit 6cf535eaef
11 changed files with 312 additions and 10 deletions
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1
default.nix
View file

@ -247,6 +247,7 @@ let
pkgs.git
pkgs.gh # github cli
pkgs.cloc
pkgs.bloaty
pkgs.lcov
pkgs.catch2

22
xo-alloc2/include/xo/alloc2/AAllocator.hpp
View file

@ -23,6 +23,10 @@ namespace xo {
reserve_exhausted,
/** unable to commit (i.e. mprotect failure) **/
commit_failed,
/** allocation size too big (See @ref ArenaConfig::header_size_mask_) **/
header_size_mask,
/** sub_alloc not preceded by super alloc (or another sub_alloc) **/
orphan_sub_alloc,
};
struct AllocatorError {
@ -67,6 +71,10 @@ namespace xo {
///@{
/** @brief type used for allocation amounts **/
using size_type = std::size_t;
/** @brief type used for allocation responses **/
using value_type = std::byte *;
/** object header, if configured **/
using header_type = std::uint64_t;
///@}
/*
@ -121,7 +129,19 @@ namespace xo {
**/
virtual bool expand(Opaque d, std::size_t z) const noexcept = 0;
/** allocate @p z bytes of memory from allocator @p d. **/
virtual std::byte * alloc(Opaque d, std::size_t z) const = 0;
virtual value_type alloc(Opaque d, size_type z) const = 0;
/** like @ref alloc, but follow with one or more consecutive
* @ref sub_alloc() calls. This sequence of allocs will share
* the initial allocation header.
**/
virtual value_type super_alloc(Opaque d, size_type z) const = 0;
/** follow a preceding @ref super_alloc call with additional
* subsidiary allocs that share the same object header.
* Must finish sequence with exactly one sub_alloc call
* with @p complete_flag set. This sub_alloc call may have
* zero @p z
**/
virtual value_type sub_alloc(Opaque d, size_type z, bool complete_flag) const = 0;
/** reset allocator @p d to empty state **/
virtual void clear(Opaque d) const = 0;
/** destruct allocator @p d **/

23
xo-alloc2/include/xo/alloc2/DArena.hpp
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@ -26,6 +26,22 @@ namespace xo {
* (provided you use their full extent :)
**/
std::size_t hugepage_z_ = 2 * 1024 * 1024;
/** true to store header (8 bytes) at the beginning of each allocation.
* necessary and sufficient to allows iterating over allocs
* present in arena
**/
bool store_header_flag_ = false;
/** if non-zero, allocate extra space between allocs, and fill
* with fixed test-pattern contents. Allows for simple
* runtime arena sanitizing checks.
* Will be rounded up to multiple of @ref padding::c_alloc_alignment
**/
std::size_t guard_z_ = 0;
/** if store_header_flag_ is true: mask bits for allocation size.
* remaining bits can be stolen for other purposes
* otherwise ignored
**/
std::uint64_t header_size_mask_ = 0xffffffff;
/** true to enable debug logging **/
bool debug_flag_ = false;
@ -59,6 +75,8 @@ namespace xo {
using size_type = std::size_t;
/** @brief a contiguous memory range **/
using range_type = std::pair<std::byte*,std::byte*>;
/** @brief type for allocation header (if enabled) **/
using header_type = std::uint64_t;
///@}
@ -103,6 +121,11 @@ namespace xo {
**/
size_type committed_z_ = 0;
/** if config_.store_header_flag_:
* Pointer to header for last allocation.
**/
header_type * last_header_ = nullptr;
/** free pointer.
* Memory in range [@ref lo_, @ref free_) current in use
**/

4
xo-alloc2/include/xo/alloc2/IAllocator_Any.hpp
View file

@ -41,7 +41,9 @@ namespace xo {
[[noreturn]] AllocatorError last_error(Copaque) const noexcept override { _fatal(); }
[[noreturn]] bool expand(Opaque, std::size_t) const noexcept override { _fatal(); }
[[noreturn]] std::byte * alloc(Opaque, std::size_t) const override { _fatal(); }
[[noreturn]] value_type alloc(Opaque, std::size_t) const override { _fatal(); }
[[noreturn]] value_type super_alloc(Opaque, std::size_t) const override { _fatal(); }
[[noreturn]] value_type sub_alloc(Opaque, std::size_t, bool) const override { _fatal(); }
[[noreturn]] void clear(Opaque) const override { _fatal(); }
[[noreturn]] void destruct_data(Opaque) const override { _fatal(); }

35
xo-alloc2/include/xo/alloc2/IAllocator_DArena.hpp
View file

@ -29,6 +29,14 @@ namespace xo {
*/
struct IAllocator_DArena {
using size_type = std::size_t;
using value_type = std::byte *;
enum class alloc_mode : uint8_t {
standard,
super,
sub,
sub_complete,
};
static std::string_view name(const DArena &) noexcept;
static size_type reserved(const DArena &) noexcept;
@ -43,11 +51,34 @@ namespace xo {
* to size at least @p z
* In practice will round up to a multiple of @ref page_z_.
**/
static bool expand(DArena & d, std::size_t z) noexcept;
static bool expand(DArena & d, size_type z) noexcept;
static std::byte * alloc(DArena &, std::size_t z);
static value_type alloc(DArena &, size_type z);
/** when store_header_flag enabled:
* like alloc(), but combine memory consumed by this alloc
* plus following consecutive sub_alloc()'s into a single header.
* otherwise equivalent to alloc()
**/
static value_type super_alloc(DArena &, size_type z);
/** when store_header_flag enabled:
* follow preceding super_alloc() by one or more sub_allocs().
* accumulate total allocated size (including padding) into
* single header. All sub_allocs() except the last must set
* @p complete_flag to false. The last sub_alloc() must set
* @p complete_flag to true.
**/
static value_type sub_alloc(DArena &, size_type z, bool complete_flag);
static void clear(DArena &);
static void destruct_data(DArena &);
private:
/** alloc driver. shared by alloc(), super_alloc(), sub_alloc() **/
static value_type _alloc(DArena &,
size_type z,
alloc_mode mode,
bool store_header_flag,
bool remember_header_flag);
};
// template <>

12
xo-alloc2/include/xo/alloc2/IAllocator_Xfer.hpp
View file

@ -18,7 +18,8 @@ namespace xo {
struct IAllocator_Xfer : public AAllocator {
// parallel interface to AAllocator, with specific data type
using Impl = IAllocator_DRepr;
using size_type = std::size_t;
using size_type = AAllocator::size_type;
using value_type = AAllocator::value_type;
static const DRepr & _dcast(Copaque d) { return *(const DRepr *)d; }
static DRepr & _dcast(Opaque d) { return *(DRepr *)d; }
@ -43,8 +44,15 @@ namespace xo {
bool expand(Opaque d,
std::size_t z) const noexcept override { return I::expand(_dcast(d), z); }
std::byte * alloc(Opaque d,
value_type alloc(Opaque d,
std::size_t z) const override { return I::alloc(_dcast(d), z); }
value_type super_alloc(Opaque d,
std::size_t z) const override { return I::super_alloc(_dcast(d), z); }
value_type sub_alloc(Opaque d,
std::size_t z,
bool complete_flag) const override {
return I::sub_alloc(_dcast(d), z, complete_flag);
}
void clear(Opaque d) const override { return I::clear(_dcast(d)); }
void destruct_data(Opaque d) const override { return I::destruct_data(_dcast(d)); }

7
xo-alloc2/include/xo/alloc2/RAllocator.hpp
View file

@ -18,6 +18,7 @@ namespace xo {
public:
using ObjectType = Object;
using size_type = std::size_t;
using value_type = std::byte *;
RAllocator() {}
RAllocator(Object::DataPtr data) : Object{std::move(data)} {}
@ -33,7 +34,11 @@ namespace xo {
AllocatorError last_error() const { return O::iface()->last_error(O::data()); }
bool expand(size_type z) { return O::iface()->expand(O::data(), z); }
std::byte * alloc(size_type z) { return O::iface()->alloc(O::data(), z); }
value_type alloc(size_type z) { return O::iface()->alloc(O::data(), z); }
value_type super_alloc(size_type z) { return O::iface()->super_alloc(O::data(), z); }
value_type sub_alloc(size_type z,
bool complete_flag) { return O::iface()->sub_alloc(O::data(),
z, complete_flag); }
static bool _valid;
};

2
xo-alloc2/include/xo/alloc2/padding.hpp
View file

@ -50,7 +50,7 @@ namespace xo {
**/
static inline
std::size_t with_padding(std::size_t z,
std::size_t align)
std::size_t align = c_alloc_alignment)
{
return z + alloc_padding(z, align);
}

3
xo-alloc2/src/alloc2/DArena.cpp
View file

@ -166,6 +166,9 @@ namespace xo {
last_error_{}
{
//retval.checkpoint_ = lo_;
/** make sure guard size is aligned **/
config_.guard_z_ = padding::with_padding(config_.guard_z_);
}
DArena::DArena(DArena && other) {

175
xo-alloc2/src/alloc2/IAllocator_DArena.cpp
View file

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

38
xo-alloc2/utest/arena.test.cpp
View file

@ -174,6 +174,44 @@ namespace xo {
REQUIRE(a1o.committed() <= a1o.reserved());
}
TEST_CASE("allocator-alloc-2", "[alloc2][Allocator]")
{
using header_type = AAllocator::header_type;
/* typed allocator a1o, with object header */
ArenaConfig cfg { .name_ = "testarena",
.size_ = 64*1024,
.store_header_flag_ = true,
/* up to 4GB */
.header_size_mask_ = 0xffffffff,
.debug_flag_ = false,
};
DArena arena = DArena::map(cfg);
obj<AAllocator, DArena> a1o{&arena};
REQUIRE(a1o.reserved() >= cfg.size_);
REQUIRE(a1o.committed() == 0);
REQUIRE(a1o.available() == 0);
REQUIRE(a1o.allocated() == 0);
size_t z0 = 1;
byte * m0 = a1o.alloc(1);
REQUIRE(m0);
header_type* header = (header_type*)(m0 - sizeof(header_type));
REQUIRE(a1o.contains(header));
REQUIRE(((*header) & cfg.header_size_mask_) == padding::with_padding(z0));
REQUIRE(a1o.last_error().error_ == error::none);
REQUIRE(a1o.last_error().error_seq_ == 0);
REQUIRE(a1o.allocated() >= z0);
REQUIRE(a1o.allocated() < sizeof(AAllocator::header_type) + z0 + padding::c_alloc_alignment );
REQUIRE(a1o.allocated() <= a1o.committed());
REQUIRE(a1o.allocated() + a1o.available() == a1o.committed());
REQUIRE(a1o.committed() <= a1o.reserved());
}
TEST_CASE("allocator-fail-1", "[alloc2][AAllocator]")
{
/* typed allocator a1o */