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xo-alloc2: + guard bytes at beginning of arena + refactoring

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This commit is contained in:
Roland Conybeare 2025-12-13 22:15:43 -05:00
commit c6b57232e8
8 changed files with 210 additions and 89 deletions
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59
xo-alloc2/include/xo/alloc2/ArenaConfig.hpp Normal file
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@ -0,0 +1,59 @@
/** @file ArenaConfig.hpp
*
* @author Roland Conybeare, Dec 2025
**/
#pragma once
#include <string>
#include <cstdint>
namespace xo {
namespace mm {
/** @class ArenaConfig
*
* @brief configuration for a @ref DArena instance
**/
struct ArenaConfig {
/** @defgroup mm-arenaconfig-instance-vars ArenaConfig members **/
///@{
/** optional name, for diagnostics **/
std::string name_;
/** desired arena size -- hard max = reserved virtual memory **/
std::size_t size_;
/** hugepage size -- using huge pages relieves some TLB pressure
* (provided you use their full extent :)
**/
std::size_t hugepage_z_ = 2 * 1024 * 1024;
/** 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 guard_z_ > 0, write at least that many copies
* of this guard byte following each complete allocation
**/
std::uint8_t guard_byte_ = 0xfd;
/** if store_header_flag_ is true: mask bits for allocation size.
* remaining bits can be stolen for other purposes
* otherwise ignored
**/
/** 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;
std::uint64_t header_size_mask_ = 0xffffffff;
/** true to enable debug logging **/
bool debug_flag_ = false;
///@}
};
} /*namespace mm*/
} /*namespace xo*/
/* end ArenaConfig.hpp */

40
xo-alloc2/include/xo/alloc2/DArena.hpp
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@ -5,49 +5,11 @@
#pragma once
#include <string>
#include "ArenaConfig.hpp"
namespace xo {
namespace mm {
/** @class ArenaConfig
*
* @brief configuration for a @ref DArena instance
**/
struct ArenaConfig {
/** @defgroup mm-arenaconfig-instance-vars ArenaConfig members **/
///@{
/** optional name, for diagnostics **/
std::string name_;
/** desired arena size -- hard max = reserved virtual memory **/
std::size_t size_;
/** hugepage size -- using huge pages relieves some TLB pressure
* (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;
///@}
};
/** @class DArena
*
* @brief represent arena allocator state

8
xo-alloc2/include/xo/alloc2/IAllocator_Any.hpp
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@ -9,9 +9,7 @@
#include <cassert>
namespace xo {
namespace mm {
struct IAllocator_Any;
}
namespace mm { struct IAllocator_Any; }
namespace facet {
template <>
@ -22,12 +20,14 @@ namespace xo {
namespace mm {
/** @class IAllocator_Any
* @brief Allocator implementation for variant instance.
* @brief Allocator implementation for empty variant instance.
**/
struct IAllocator_Any : public AAllocator {
//using Impl = IAllocator_ImplType<xo::facet::DVariantPlaceholder>;
using size_type = std::size_t;
const AAllocator * iface() const { return std::launder(this); }
// from AAllocator
int32_t _typeseq() const noexcept override { return s_typeseq; }

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

@ -34,7 +34,7 @@ namespace xo {
enum class alloc_mode : uint8_t {
standard,
super,
sub,
sub_incomplete,
sub_complete,
};
@ -75,10 +75,7 @@ namespace xo {
/** 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);
alloc_mode mode);
};
// template <>