xo-alloc2: add guard-byte spans to AllocInfo
This commit is contained in:
parent
1dc221e65f
commit
5a5de795c1
8 changed files with 231 additions and 175 deletions
|
|
@ -36,118 +36,6 @@ namespace xo {
|
|||
|
||||
static_assert(sizeof(AllocHeader) == sizeof(AllocHeader::repr_type));
|
||||
static_assert(std::is_standard_layout_v<AllocHeader>);
|
||||
|
||||
/*
|
||||
* Each allocation is preceded by a 64-bit header.
|
||||
* Header is split into 3 configurable-width bit fields,
|
||||
* labelled (from hi to lo bit order) {tseq, age, size}.
|
||||
*
|
||||
* 1. tseq. seq# identifying object types; needed for gc.
|
||||
* 2. gen. age cohort; increases when alloc survives gc.
|
||||
* 3. size. alloc size.
|
||||
*
|
||||
* Arena allocator only uses size.
|
||||
* X1 collector uses {tseq, gen, size}
|
||||
*
|
||||
* alloc header
|
||||
*
|
||||
* TTTTTTTTTTTTGGGGGZZZZZZZZZZZZ
|
||||
* < tseq ><gen>< size >
|
||||
*
|
||||
* masking
|
||||
*
|
||||
* ..432107654321076543210 bit
|
||||
*
|
||||
* > < .gen_bits
|
||||
* 0..............01111111 gen_mask_unshifted
|
||||
* 0..011111110..........0 gen_mask_shifted
|
||||
* > < gen_shift
|
||||
*/
|
||||
struct AllocHeaderConfig {
|
||||
using repr_type = AllocHeader;
|
||||
|
||||
AllocHeaderConfig() = default;
|
||||
AllocHeaderConfig(std::uint8_t t, std::uint8_t a, std::uint8_t z) noexcept
|
||||
: tseq_bits_{t}, age_bits_{a}, size_bits_{z} {}
|
||||
|
||||
std::uint64_t tseq_mask() const noexcept {
|
||||
// e.g.
|
||||
// FF FF FF 00 00 00 00 00
|
||||
// with tseq_bits=24, age_bits=8, size_bits=32
|
||||
//
|
||||
return ((1ul << tseq_bits_) - 1) << (age_bits_ + size_bits_);
|
||||
}
|
||||
|
||||
std::uint64_t age_mask() const noexcept {
|
||||
// e.g.
|
||||
// 00 00 00 FF 00 00 00 00
|
||||
// with age_bits=8, size_bits=32
|
||||
//
|
||||
return ((1ul << age_bits_) - 1) << size_bits_;
|
||||
}
|
||||
|
||||
std::uint64_t size_mask() const noexcept {
|
||||
// e.g.
|
||||
// 00 00 00 00 FF FF FF FF
|
||||
// with size_bits=32
|
||||
//
|
||||
return ((1ul << size_bits_) - 1);
|
||||
}
|
||||
|
||||
/** extract type id from alloc header @p hdr **/
|
||||
std::uint32_t tseq(repr_type hdr) const noexcept {
|
||||
// e.g.
|
||||
// 0x302010
|
||||
// for header
|
||||
// 30 20 10 -- -- -- -- --
|
||||
// with tseq_bits_ = 24, age_bits_ + size_bits_ = 40
|
||||
//
|
||||
return (hdr.repr_ & tseq_mask()) >> (age_bits_ + size_bits_);
|
||||
}
|
||||
|
||||
/** extract age from alloc header @p hdr **/
|
||||
std::uint32_t age(repr_type hdr) const noexcept {
|
||||
// e.g.
|
||||
// 0xa0
|
||||
// for header
|
||||
// -- -- -- a0 -- -- -- --
|
||||
// with age_bits_ = 8, size_bits_ = 32
|
||||
//
|
||||
return (hdr.repr_ & age_mask()) >> size_bits_;
|
||||
}
|
||||
|
||||
/** extract size from alloc header @p hdr **/
|
||||
std::size_t size(repr_type hdr) const noexcept {
|
||||
// e.g.
|
||||
// 0x01020300
|
||||
// for header
|
||||
// -- -- -- -- 01 02 03 00
|
||||
// with size_bits_ = 32
|
||||
//
|
||||
return (hdr.repr_ & size_mask());
|
||||
}
|
||||
|
||||
/** true iff sentinel tseq, flagging a forwarding pointer **/
|
||||
bool is_forwarding_tseq(repr_type hdr) const noexcept {
|
||||
// e.g.
|
||||
// 0xFFFFFF
|
||||
// i.e. header
|
||||
// FF FF FF -- -- -- -- --
|
||||
// with tseq_bits_ = 24, age_bits + size_bits_ = 40
|
||||
//
|
||||
return (hdr.repr_ & tseq_mask()) == tseq_mask();
|
||||
}
|
||||
|
||||
bool is_size_enabled() const noexcept { return size_bits_ > 0; }
|
||||
|
||||
/** number of bits for tseq **/
|
||||
std::uint8_t tseq_bits_ = 24;
|
||||
/** number of bits for age **/
|
||||
std::uint8_t age_bits_ = 8;
|
||||
/** number of bits for size **/
|
||||
std::uint8_t size_bits_ = 32;
|
||||
};
|
||||
|
||||
}
|
||||
}
|
||||
|
||||
|
|
|
|||
144
xo-alloc2/include/xo/alloc2/alloc/AllocHeaderConfig.hpp
Normal file
144
xo-alloc2/include/xo/alloc2/alloc/AllocHeaderConfig.hpp
Normal file
|
|
@ -0,0 +1,144 @@
|
|||
/** @file AllocHeaderConfig.hpp
|
||||
*
|
||||
* @author Roland Conybeare, Dec 2025
|
||||
**/
|
||||
|
||||
#pragma once
|
||||
|
||||
#include "AllocHeader.hpp"
|
||||
#include <utility>
|
||||
|
||||
namespace xo {
|
||||
namespace mm {
|
||||
/*
|
||||
* Each allocation is preceded by a 64-bit header.
|
||||
* Header is split into 3 configurable-width bit fields,
|
||||
* labelled (from hi to lo bit order) {tseq, age, size}.
|
||||
*
|
||||
* 1. tseq. seq# identifying object types; needed for gc.
|
||||
* 2. gen. age cohort; increases when alloc survives gc.
|
||||
* 3. size. alloc size.
|
||||
*
|
||||
* Arena allocator only uses size.
|
||||
* X1 collector uses {tseq, gen, size}
|
||||
*
|
||||
* alloc header
|
||||
*
|
||||
* TTTTTTTTTTTTGGGGGZZZZZZZZZZZZ
|
||||
* < tseq ><gen>< size >
|
||||
*
|
||||
* masking
|
||||
*
|
||||
* ..432107654321076543210 bit
|
||||
*
|
||||
* > < .gen_bits
|
||||
* 0..............01111111 gen_mask_unshifted
|
||||
* 0..011111110..........0 gen_mask_shifted
|
||||
* > < gen_shift
|
||||
*/
|
||||
struct AllocHeaderConfig {
|
||||
using repr_type = AllocHeader;
|
||||
using span_type = std::pair<const std::byte *, const std::byte *>;
|
||||
|
||||
AllocHeaderConfig() = default;
|
||||
AllocHeaderConfig(std::uint32_t gz,
|
||||
std::uint8_t guard_byte,
|
||||
std::uint8_t t,
|
||||
std::uint8_t a,
|
||||
std::uint8_t z) noexcept : guard_z_{gz},
|
||||
guard_byte_{guard_byte},
|
||||
tseq_bits_{t},
|
||||
age_bits_{a},
|
||||
size_bits_{z} {}
|
||||
|
||||
std::uint64_t tseq_mask() const noexcept {
|
||||
// e.g.
|
||||
// FF FF FF 00 00 00 00 00
|
||||
// with tseq_bits=24, age_bits=8, size_bits=32
|
||||
//
|
||||
return ((1ul << tseq_bits_) - 1) << (age_bits_ + size_bits_);
|
||||
}
|
||||
|
||||
std::uint64_t age_mask() const noexcept {
|
||||
// e.g.
|
||||
// 00 00 00 FF 00 00 00 00
|
||||
// with age_bits=8, size_bits=32
|
||||
//
|
||||
return ((1ul << age_bits_) - 1) << size_bits_;
|
||||
}
|
||||
|
||||
std::uint64_t size_mask() const noexcept {
|
||||
// e.g.
|
||||
// 00 00 00 00 FF FF FF FF
|
||||
// with size_bits=32
|
||||
//
|
||||
return ((1ul << size_bits_) - 1);
|
||||
}
|
||||
|
||||
/** extract type id from alloc header @p hdr **/
|
||||
std::uint32_t tseq(repr_type hdr) const noexcept {
|
||||
// e.g.
|
||||
// 0x302010
|
||||
// for header
|
||||
// 30 20 10 -- -- -- -- --
|
||||
// with tseq_bits_ = 24, age_bits_ + size_bits_ = 40
|
||||
//
|
||||
return (hdr.repr_ & tseq_mask()) >> (age_bits_ + size_bits_);
|
||||
}
|
||||
|
||||
/** extract age from alloc header @p hdr **/
|
||||
std::uint32_t age(repr_type hdr) const noexcept {
|
||||
// e.g.
|
||||
// 0xa0
|
||||
// for header
|
||||
// -- -- -- a0 -- -- -- --
|
||||
// with age_bits_ = 8, size_bits_ = 32
|
||||
//
|
||||
return (hdr.repr_ & age_mask()) >> size_bits_;
|
||||
}
|
||||
|
||||
/** extract size from alloc header @p hdr **/
|
||||
std::size_t size(repr_type hdr) const noexcept {
|
||||
// e.g.
|
||||
// 0x01020300
|
||||
// for header
|
||||
// -- -- -- -- 01 02 03 00
|
||||
// with size_bits_ = 32
|
||||
//
|
||||
return (hdr.repr_ & size_mask());
|
||||
}
|
||||
|
||||
/** true iff sentinel tseq, flagging a forwarding pointer **/
|
||||
bool is_forwarding_tseq(repr_type hdr) const noexcept {
|
||||
// e.g.
|
||||
// 0xFFFFFF
|
||||
// i.e. header
|
||||
// FF FF FF -- -- -- -- --
|
||||
// with tseq_bits_ = 24, age_bits + size_bits_ = 40
|
||||
//
|
||||
return (hdr.repr_ & tseq_mask()) == tseq_mask();
|
||||
}
|
||||
|
||||
bool is_size_enabled() const noexcept { return size_bits_ > 0; }
|
||||
|
||||
/** 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::uint32_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;
|
||||
/** number of bits for tseq **/
|
||||
std::uint8_t tseq_bits_ = 24;
|
||||
/** number of bits for age **/
|
||||
std::uint8_t age_bits_ = 8;
|
||||
/** number of bits for size **/
|
||||
std::uint8_t size_bits_ = 32;
|
||||
};
|
||||
} /*namespace mm*/
|
||||
} /*namespace xo*/
|
||||
|
||||
/* end AllocHeaderConfig.hpp */
|
||||
|
|
@ -5,7 +5,8 @@
|
|||
|
||||
#pragma once
|
||||
|
||||
#include "AllocHeader.hpp"
|
||||
#include "AllocHeaderConfig.hpp"
|
||||
#include <utility>
|
||||
|
||||
namespace xo {
|
||||
namespace mm {
|
||||
|
|
@ -18,16 +19,34 @@ namespace xo {
|
|||
**/
|
||||
struct AllocInfo {
|
||||
using size_type = AllocHeader::size_type;
|
||||
using byte = std::byte;
|
||||
using span_type = std::pair<const byte *, const byte *>;
|
||||
|
||||
AllocInfo(const AllocHeaderConfig * p_cfg, const AllocHeader * p_hdr)
|
||||
: p_config_{p_cfg}, p_header_{p_hdr} {}
|
||||
AllocInfo(const AllocHeaderConfig * p_cfg,
|
||||
const byte * p_guard_lo,
|
||||
const AllocHeader * p_hdr,
|
||||
const byte * p_guard_hi) : p_config_{p_cfg},
|
||||
p_guard_lo_{p_guard_lo},
|
||||
p_header_{p_hdr},
|
||||
p_guard_hi_{p_guard_hi} {}
|
||||
|
||||
/** error when alloc-header not configured **/
|
||||
static AllocInfo error_not_configured(AllocHeaderConfig * p_cfg) { return AllocInfo(p_cfg, nullptr); }
|
||||
static AllocInfo error_not_configured(AllocHeaderConfig * p_cfg) {
|
||||
return AllocInfo(p_cfg, nullptr, nullptr, nullptr);
|
||||
}
|
||||
|
||||
/** true for non-sentinel AllocInfo instance **/
|
||||
bool is_valid() const { return (p_config_ != nullptr) && (p_header_ != nullptr); }
|
||||
|
||||
/** Guard bytes preceding allocation-header **/
|
||||
span_type guard_lo() const noexcept {
|
||||
if (!p_guard_lo_)
|
||||
return span_type(nullptr, nullptr);
|
||||
|
||||
return span_type(p_guard_lo_,
|
||||
p_guard_lo_ + p_config_->guard_z_);
|
||||
}
|
||||
|
||||
/** Type sequence number in garbage collector **/
|
||||
std::uint32_t tseq() const noexcept { return p_config_->tseq(*p_header_); }
|
||||
/** Allocation age in garbage collector **/
|
||||
|
|
@ -35,8 +54,19 @@ namespace xo {
|
|||
/** Allocation size (including allocator-supplied padding) **/
|
||||
size_type size() const noexcept { return p_config_->size(*p_header_); }
|
||||
|
||||
/** Guard bytes immediately following allocation **/
|
||||
span_type guard_hi() const noexcept {
|
||||
if (!p_guard_hi_)
|
||||
return span_type(nullptr, nullptr);
|
||||
|
||||
return span_type(p_guard_hi_,
|
||||
p_guard_hi_ + p_config_->guard_z_);
|
||||
}
|
||||
|
||||
const AllocHeaderConfig * p_config_ = nullptr;
|
||||
const byte * p_guard_lo_ = nullptr;
|
||||
const AllocHeader * p_header_ = nullptr;
|
||||
const byte * p_guard_hi_ = nullptr;
|
||||
};
|
||||
} /*namespace mm*/
|
||||
} /*namespace xo*/
|
||||
|
|
|
|||
|
|
@ -29,20 +29,6 @@ namespace xo {
|
|||
* (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
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue