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Implemented Region. Arena allocator now uses Region for OS specific allocation and page management.
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This commit is contained in:
Kearwood Gilbert
2026-08-15 15:50:32 -07:00
parent 3a6711a942
commit e358b02bea
6 changed files with 225 additions and 78 deletions
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85
src/arena.cpp
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@@ -40,10 +40,7 @@ namespace mimir {
Arena::Arena()
: m_minSize(0)
, m_maxSize(0)
, m_data(nullptr)
, m_usedSize(0)
, m_committedSize(0)
{
for (size_t i = 0; i < kWatermarkLen; i++) {
m_watermark[i] = 0;
@@ -52,73 +49,31 @@ Arena::Arena()
Arena::~Arena()
{
if (m_data) {
#if defined(_WIN32) || defined(_WIN64)
if (!VirtualFree((void*)m_data, 0, MEM_RELEASE)) {
ReportWindowsLastError("VirtualAlloc");
}
#elif defined(__unix__) || defined(__APPLE__) || defined(ANDROID)
munmap(m_data, KRAKEN_MEM_ROUND_UP_PAGE(m_maxSize));
#else
static_assert(false, "Not Implemented");
#endif
}
}
bool Arena::init(size_t minSize, size_t maxSize)
{
assert(maxSize >= minSize);
assert(m_data == nullptr);
assert(m_usedSize == 0);
assert(m_committedSize == 0);
m_minSize = KRAKEN_MEM_ROUND_UP_PAGE(minSize);
m_maxSize = KRAKEN_MEM_ROUND_UP_PAGE(maxSize);
#if defined(_WIN32) || defined(_WIN64)
m_data = (std::byte*)VirtualAlloc(NULL, KRAKEN_MEM_ROUND_UP_PAGE(m_maxSize), MEM_RESERVE, PAGE_NOACCESS);
if (m_data == nullptr) {
ReportWindowsLastError("VirtualAlloc");
return false;
}
#elif defined(__unix__) || defined(__APPLE__) || defined(ANDROID)
m_data = (std::byte*)mmap(NULL, KRAKEN_MEM_ROUND_UP_PAGE(m_maxSize), PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (m_data == MAP_FAILED) {
return false;
}
#else
static_assert(false, "Not Implemented");
#endif
return true;
return m_region.init(maxSize);
}
std::byte* Arena::alloc(size_t size)
{
size_t neededSize = m_usedSize + size;
if (neededSize > m_committedSize)
if (neededSize > m_region.getSize())
{
// Increase the size exponentially when we run out
size_t newSize = std::bit_ceil(neededSize) << 1;
if (newSize < m_minSize) {
newSize = m_minSize;
}
newSize = KRAKEN_MEM_ROUND_UP_PAGE(newSize);
m_region.resize(newSize);
}
#if defined(_WIN32) || defined(_WIN64)
if(VirtualAlloc(m_data + m_committedSize, newSize - m_committedSize, MEM_COMMIT, PAGE_READWRITE) == nullptr) {
ReportWindowsLastError("VirtualAlloc");
return nullptr;
}
#elif defined(__unix__) || defined(__APPLE__) || defined(ANDROID)
if (mprotect(m_data + m_committedSize, newSize - m_committedSize, PROT_READ | PROT_WRITE) != 0) {
return nullptr;
}
#else
static_assert(false, "Not Implemented");
#endif
m_committedSize = newSize;
} // if (neededSize > m_committedSize)
std::byte* ret = m_data + m_usedSize;
std::byte* ret = m_region.getAddress() + m_usedSize;
m_usedSize = neededSize;
return ret;
}
@@ -131,7 +86,7 @@ std::byte* Arena::allocA16(size_t size)
return nullptr;
}
return m_data + nextByte;
return m_region.getAddress() + nextByte;
}
std::byte* Arena::allocA64(size_t size)
@@ -142,7 +97,7 @@ std::byte* Arena::allocA64(size_t size)
return nullptr;
}
return m_data + nextByte;
return m_region.getAddress() + nextByte;
}
void Arena::reset()
@@ -161,28 +116,8 @@ void Arena::reset()
targetSize = m_minSize;
}
size_t thresholdSize = targetSize << 1; // The threshold for shrinking is greater than the target to implement hysteresis
if (m_committedSize > thresholdSize) {
size_t newSize = KRAKEN_MEM_ROUND_UP_PAGE(targetSize);
std::byte* rangeStart = m_data + newSize;
size_t rangeLen = m_committedSize - newSize;
#if defined(_WIN32) || defined(_WIN64)
if (!VirtualAlloc(rangeStart, rangeLen, MEM_RESET, PAGE_NOACCESS)) {
ReportWindowsLastError("VirtualAlloc");
} else {
m_committedSize = newSize;
}
#elif defined(__unix__) || defined(__APPLE__) || defined(ANDROID)
if (madvise(rangeStart, rangeLen, MADV_DONTNEED) != 0) {
// TODO - Log Error or debug build assert
}
if (mprotect(rangeStart, rangeLen, PROT_NONE) != 0) {
// TODO - Log Error or debug build assert
}
#else
static_assert(false, "Not Implemented");
#endif
m_committedSize = newSize;
if (m_region.getSize() > thresholdSize) {
m_region.resize(targetSize);
}
m_usedSize = 0;