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Get rid of the memory manager from buffer.

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This commit is contained in:
Sandu Liviu Catalin 2021-01-29 00:20:09 +02:00
parent 9efcfe2fa9
commit b6a270293b
2 changed files with 16 additions and 561 deletions
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384
module/Base/Buffer.cpp
View File

@ -5,7 +5,6 @@
// ------------------------------------------------------------------------------------------------
#include <cstdlib>
#include <cstring>
#include <exception>
#include <stdexcept>
// ------------------------------------------------------------------------------------------------
@ -47,343 +46,11 @@ void ThrowMemExcept(const char * msg, ...)
throw Sqrat::Exception(buffer); // NOLINT(hicpp-exception-baseclass,cert-err60-cpp)
}
/* ------------------------------------------------------------------------------------------------
* Allocate a memory buffer and return it.
*/
static Buffer::Pointer AllocMem(Buffer::SzType size)
{
// Attempt to allocate memory directly
auto ptr = reinterpret_cast< Buffer::Pointer >(std::malloc(size));
// Validate the allocated memory
if (!ptr)
{
ThrowMemExcept("Unable to allocate (%u) bytes of memory", size);
}
// Return the allocated memory
return ptr;
}
/* ------------------------------------------------------------------------------------------------
* ...
*/
class MemCat
{
// --------------------------------------------------------------------------------------------
friend class Memory;
friend class Buffer;
public:
// --------------------------------------------------------------------------------------------
typedef Buffer::Value Value; // The type of value used to represent a byte.
// --------------------------------------------------------------------------------------------
typedef Buffer::Reference Reference; // A reference to the stored value type.
typedef Buffer::ConstRef ConstRef; // A const reference to the stored value type.
// --------------------------------------------------------------------------------------------
typedef Buffer::Pointer Pointer; // A pointer to the stored value type.
typedef Buffer::ConstPtr ConstPtr; // A const pointer to the stored value type.
// --------------------------------------------------------------------------------------------
typedef Buffer::SzType SzType; // The type used to represent size in general.
private:
/* --------------------------------------------------------------------------------------------
* Structure used to store a memory chunk in the linked list.
*/
struct Node
{
// ----------------------------------------------------------------------------------------
SzType mCap; // The size of the memory chunk.
Pointer mPtr; // Pointer to the memory chunk.
Node* mNext; // The next node in the list.
/* ----------------------------------------------------------------------------------------
* Base constructor.
*/
explicit Node(Node * next)
: mCap(0)
, mPtr(nullptr)
, mNext(next)
{
/* ... */
}
};
// --------------------------------------------------------------------------------------------
static Node * s_Nodes; /* List of unused node instances. */
// --------------------------------------------------------------------------------------------
Node* m_Head; /* The head memory node. */
/* --------------------------------------------------------------------------------------------
* Default constructor.
*/
MemCat()
: m_Head(nullptr)
{
/* ... */
}
/* --------------------------------------------------------------------------------------------
* Destructor.
*/
~MemCat()
{
for (Node * node = m_Head, * next = nullptr; node; node = next)
{
// Free the memory (if any)
if (node->mPtr)
{
std::free(node->mPtr);
}
// Save the next node
next = node->mNext;
// Release the node instance
delete node;
}
// Explicitly set the head node to null
m_Head = nullptr;
}
/* --------------------------------------------------------------------------------------------
* Clear all memory buffers from the pool.
*/
void Clear()
{
for (Node * node = m_Head, * next = nullptr; node; node = next)
{
// Free the memory (if any)
if (node->mPtr)
{
free(node->mPtr);
}
// Save the next node
next = node->mNext;
// Release the node instance
Push(node);
}
// Explicitly set the head node to null
m_Head = nullptr;
}
/* --------------------------------------------------------------------------------------------
* Grab a memory buffer from the pool.
*/
void Grab(Pointer & ptr, SzType & size)
{
// NOTE: Function assumes (size > 0)
// Find a buffer large enough to satisfy the requested size
for (Node * node = m_Head, * prev = nullptr; node; prev = node, node = node->mNext)
{
// Is this buffer large enough?
if (node->mCap >= size)
{
// Was there a previous node?
if (prev)
{
prev->mNext = node->mNext;
}
// Probably this was the head
else
{
m_Head = node->mNext;
}
// Assign the memory
ptr = node->mPtr;
// Assign the size
size = node->mCap;
// Release the node instance
Push(node);
// Exit the function
return;
}
}
// Round up the size to a power of two number
size = (size & (size - 1)) ? NextPow2(size) : size;
// Allocate the memory directly
ptr = AllocMem(size);
// See if the memory could be allocated
// (shouldn't reach this point if allocation failed)
if (!ptr)
{
// Revert the size
size = 0;
// Throw the exception
ThrowMemExcept("Unable to allocate (%u) bytes of memory", size);
}
}
/* --------------------------------------------------------------------------------------------
* Return a memory buffer to the pool.
*/
void Drop(Pointer & ptr, SzType & size)
{
if (!ptr)
{
ThrowMemExcept("Cannot store invalid memory buffer");
}
// Request a node instance
Node * node = Pull();
// Assign the specified memory
node->mPtr = ptr;
// Assign the specified size
node->mCap = size;
// Demote the current head node
node->mNext = m_Head;
// Promote as the head node
m_Head = node;
}
/* --------------------------------------------------------------------------------------------
* Allocate a group of nodes and pool them for later use.
*/
static void Make()
{
for (SzType n = 16; n; --n)
{
// Create a new node instance
s_Nodes = new Node(s_Nodes);
// Validate the head node
if (!s_Nodes)
{
ThrowMemExcept("Unable to allocate memory nodes");
}
}
}
/* --------------------------------------------------------------------------------------------
* Retrieve an unused node from the free list.
*/
static Node * Pull()
{
// Are there any nodes available?
if (!s_Nodes)
{
Make(); // Make some!
}
// Grab the head node
Node * node = s_Nodes;
// Promote the next node as the head
s_Nodes = node->mNext;
// Return the node
return node;
}
/* --------------------------------------------------------------------------------------------
* Return a node to the free list.
*/
static void Push(Node * node)
{
// See if the node is even valid
if (!node)
{
ThrowMemExcept("Attempting to push invalid node");
}
else
{
// Demote the current head node
node->mNext = s_Nodes;
// Promote as the head node
s_Nodes = node;
}
}
};
// ------------------------------------------------------------------------------------------------
MemCat::Node * MemCat::s_Nodes = nullptr;
/* ------------------------------------------------------------------------------------------------
* Lightweight memory allocator to reduce the overhead of small allocations.
*/
class Memory
{
// --------------------------------------------------------------------------------------------
friend class Buffer; // Allow the buffer type to access the memory categories.
friend class MemRef; // Allow the memory manager reference to create new instances.
private:
/* --------------------------------------------------------------------------------------------
* Default constructor.
*/
Memory()
: m_Small()
, m_Medium()
, m_Large()
{
// Allocate several nodes for when memory starts pooling
MemCat::Make();
}
/* --------------------------------------------------------------------------------------------
* Destructor.
*/
~Memory()
{
for (MemCat::Node * node = MemCat::s_Nodes, * next = nullptr; node; node = next)
{
// Save the next node
next = node->mNext;
// Release the node instance
delete node;
}
// Explicitly set the head node to null
MemCat::s_Nodes = nullptr;
}
private:
// --------------------------------------------------------------------------------------------
MemCat m_Small; // Small memory allocations of <= 1024 bytes.
MemCat m_Medium; // Medium memory allocations of <= 4096 bytes.
MemCat m_Large; // Large memory allocations of <= 4096 bytes.
};
// ------------------------------------------------------------------------------------------------
MemRef MemRef::s_Mem{nullptr};
// ------------------------------------------------------------------------------------------------
void MemRef::Grab()
{
if (m_Ptr)
{
++(*m_Ref);
}
}
// ------------------------------------------------------------------------------------------------
void MemRef::Drop()
{
if (m_Ptr && --(*m_Ref) == 0)
{
delete m_Ptr;
delete m_Ref;
m_Ptr = nullptr;
m_Ref = nullptr;
}
}
// ------------------------------------------------------------------------------------------------
const MemRef & MemRef::Get()
{
if (!s_Mem.m_Ptr)
{
s_Mem.m_Ptr = new Memory();
s_Mem.m_Ref = new Counter(1);
}
return s_Mem;
}
// ------------------------------------------------------------------------------------------------
Buffer::Buffer(const Buffer & o)
: m_Ptr(nullptr)
, m_Cap(o.m_Cap)
, m_Cur(o.m_Cur)
, m_Mem(o.m_Mem)
{
if (m_Cap)
{
@ -445,7 +112,7 @@ Buffer & Buffer::operator = (const Buffer & o) // NOLINT(cert-oop54-cpp)
void Buffer::Grow(SzType n)
{
// Backup the current memory
Buffer bkp(m_Ptr, m_Cap, m_Cur, m_Mem);
Buffer bkp(m_Ptr, m_Cap, m_Cur);
// Acquire a bigger buffer
Request(bkp.m_Cap + n);
// Copy the data from the old buffer
@ -458,27 +125,13 @@ void Buffer::Grow(SzType n)
void Buffer::Request(SzType n)
{
// NOTE: Function assumes (n > 0)
// Is there a memory manager available?
if (!m_Mem)
{
// Round up the size to a power of two number
n = (n & (n - 1)) ? NextPow2(n) : n;
// Allocate the memory directly
m_Ptr = AllocMem(n);
}
// Find out in which category does this buffer reside
else if (n <= 1024)
{
m_Mem->m_Small.Grab(m_Ptr, n);
}
else if (n <= 4096)
{
m_Mem->m_Medium.Grab(m_Ptr, n);
}
else
{
m_Mem->m_Large.Grab(m_Ptr, n);
}
assert(n > 0);
// Round up the size to a power of two number
n = (n & (n - 1)) ? NextPow2(n) : n;
// Release previous memory if any
delete[] m_Ptr; // Implicitly handles null!
// Attempt to allocate memory
m_Ptr = new Value[n];
// If no errors occurred then we can set the size
m_Cap = n;
}
@ -486,25 +139,8 @@ void Buffer::Request(SzType n)
// ------------------------------------------------------------------------------------------------
void Buffer::Release()
{
// TODO: Implement a limit on how much memory can actually be pooled.
// Is there a memory manager available?
if (!m_Mem)
{
std::free(m_Ptr); // Deallocate the memory directly
}
// Find out to which category does this buffer belong
else if (m_Cap <= 1024)
{
m_Mem->m_Small.Drop(m_Ptr, m_Cap);
}
else if (m_Cap <= 4096)
{
m_Mem->m_Medium.Drop(m_Ptr, m_Cap);
}
else
{
m_Mem->m_Large.Drop(m_Ptr, m_Cap);
}
// Deallocate the memory
delete[] m_Ptr; // Implicitly handles null!
// Explicitly reset the buffer
m_Ptr = nullptr;
m_Cap = 0;

193
module/Base/Buffer.hpp
View File

@ -11,178 +11,6 @@
// ------------------------------------------------------------------------------------------------
namespace SqMod {
// ------------------------------------------------------------------------------------------------
class Memory;
class Buffer;
/* ------------------------------------------------------------------------------------------------
* A counted reference to a memory manager instance.
*/
class MemRef
{
private:
// --------------------------------------------------------------------------------------------
static MemRef s_Mem;
// --------------------------------------------------------------------------------------------
typedef unsigned int Counter;
// --------------------------------------------------------------------------------------------
Memory* m_Ptr; // The memory manager instance.
Counter* m_Ref; // Reference count to the managed instance.
/* --------------------------------------------------------------------------------------------
* Grab a strong reference to a memory manager.
*/
void Grab();
/* --------------------------------------------------------------------------------------------
* Drop a strong reference to a memory manager.
*/
void Drop();
public:
/* --------------------------------------------------------------------------------------------
* Get a reference to the global memory manager instance.
*/
static const MemRef & Get();
/* --------------------------------------------------------------------------------------------
* Default constructor (null).
*/
MemRef() noexcept
: m_Ptr(s_Mem.m_Ptr)
, m_Ref(s_Mem.m_Ref)
{
Grab();
}
/* --------------------------------------------------------------------------------------------
* Default constructor (null).
*/
explicit MemRef(std::nullptr_t) noexcept
: m_Ptr(nullptr)
, m_Ref(nullptr)
{
}
/* --------------------------------------------------------------------------------------------
* Copy constructor.
*/
MemRef(const MemRef & o) noexcept
: m_Ptr(o.m_Ptr)
, m_Ref(o.m_Ref)
{
Grab();
}
/* --------------------------------------------------------------------------------------------
* Move constructor.
*/
MemRef(MemRef && o) noexcept
: m_Ptr(o.m_Ptr), m_Ref(o.m_Ref)
{
o.m_Ptr = nullptr;
o.m_Ref = nullptr;
}
/* --------------------------------------------------------------------------------------------
* Destructor.
*/
~MemRef()
{
Drop();
}
/* --------------------------------------------------------------------------------------------
* Copy assignment operator.
*/
MemRef & operator = (const MemRef & o) noexcept // NOLINT(bugprone-unhandled-self-assignment,cert-oop54-cpp)
{
if (m_Ptr != o.m_Ptr)
{
Drop();
m_Ptr = o.m_Ptr;
m_Ref = o.m_Ref;
Grab();
}
return *this;
}
/* --------------------------------------------------------------------------------------------
* Move assignment operator.
*/
MemRef & operator = (MemRef && o) noexcept
{
if (m_Ptr != o.m_Ptr)
{
Drop();
m_Ptr = o.m_Ptr;
m_Ref = o.m_Ref;
o.m_Ptr = nullptr;
o.m_Ref = nullptr;
}
return *this;
}
/* --------------------------------------------------------------------------------------------
* Perform an equality comparison between two memory managers.
*/
bool operator == (const MemRef & o) const
{
return (m_Ptr == o.m_Ptr);
}
/* --------------------------------------------------------------------------------------------
* Perform an inequality comparison between two memory managers.
*/
bool operator != (const MemRef & o) const
{
return (m_Ptr != o.m_Ptr);
}
/* --------------------------------------------------------------------------------------------
* Implicit conversion to boolean for use in boolean operations.
*/
operator bool () const // NOLINT(google-explicit-constructor,hicpp-explicit-conversions)
{
return static_cast<bool>(m_Ptr);
}
/* --------------------------------------------------------------------------------------------
* Member operator for dereferencing the managed pointer.
*/
Memory * operator -> () const
{
assert(m_Ptr);
return m_Ptr;
}
/* --------------------------------------------------------------------------------------------
* Indirection operator for obtaining a reference of the managed pointer.
*/
Memory & operator * () const
{
assert(m_Ptr);
return *m_Ptr;
}
/* --------------------------------------------------------------------------------------------
* Release the reference to the managed instance.
*/
void Reset()
{
if (m_Ptr)
{
Drop();
}
}
};
// ------------------------------------------------------------------------------------------------
void ThrowMemExcept(const char * msg, ...);
@ -207,16 +35,18 @@ public:
// --------------------------------------------------------------------------------------------
typedef unsigned int SzType; // The type used to represent size in general.
// --------------------------------------------------------------------------------------------
static_assert(sizeof(Value) == 1, "Value type must be 1 byte");
private:
/* --------------------------------------------------------------------------------------------
* Construct and take ownership of the specified buffer.
*/
Buffer(Pointer & ptr, SzType & cap, SzType & cur, MemRef mem)
Buffer(Pointer & ptr, SzType & cap, SzType & cur)
: m_Ptr(ptr)
, m_Cap(cap)
, m_Cur(cur)
, m_Mem(std::move(mem))
{
ptr = nullptr;
cap = 0;
@ -240,7 +70,6 @@ public:
: m_Ptr(nullptr)
, m_Cap(0)
, m_Cur(0)
, m_Mem(MemRef::Get())
{
/* ... */
}
@ -252,7 +81,6 @@ public:
: m_Ptr(nullptr)
, m_Cap(0)
, m_Cur(0)
, m_Mem(MemRef::Get())
{
Request(size < 8 ? 8 : size);
}
@ -264,7 +92,6 @@ public:
: m_Ptr(nullptr)
, m_Cap(0)
, m_Cur(0)
, m_Mem(MemRef::Get())
{
Request(size < 8 ? 8 : size);
Move(pos);
@ -277,7 +104,6 @@ public:
: m_Ptr(nullptr)
, m_Cap(0)
, m_Cur(0)
, m_Mem(MemRef::Get())
{
Request(size < 8 ? 8 : size);
m_Cur += Write(m_Cur, data, size);
@ -290,7 +116,6 @@ public:
: m_Ptr(nullptr)
, m_Cap(0)
, m_Cur(0)
, m_Mem(MemRef::Get())
{
Request(size < 8 ? 8 : size);
Write(m_Cur, data, size);
@ -309,7 +134,6 @@ public:
: m_Ptr(o.m_Ptr)
, m_Cap(o.m_Cap)
, m_Cur(o.m_Cur)
, m_Mem(std::forward< MemRef >(o.m_Mem))
{
o.m_Ptr = nullptr;
}
@ -338,7 +162,6 @@ public:
m_Ptr = o.m_Ptr;
m_Cap = o.m_Cap;
m_Cur = o.m_Cur;
m_Mem = o.m_Mem;
o.m_Ptr = nullptr;
}
return *this;
@ -882,7 +705,7 @@ public:
else if (n > m_Cap)
{
// Backup the current memory
Buffer bkp(m_Ptr, m_Cap, m_Cur, m_Mem);
Buffer bkp(m_Ptr, m_Cap, m_Cur);
// Request the memory
Request(n * sizeof(T));
// Return the backup
@ -904,7 +727,7 @@ public:
}
/* --------------------------------------------------------------------------------------------
* Release the managed memory and manager.
* Release the managed memory.
*/
void ResetAll()
{
@ -912,7 +735,6 @@ public:
{
Release();
}
m_Mem.Reset();
}
/* --------------------------------------------------------------------------------------------
@ -1024,9 +846,6 @@ private:
Pointer m_Ptr; /* Pointer to the memory buffer. */
SzType m_Cap; /* The total size of the buffer. */
SzType m_Cur; /* The buffer edit cursor. */
// --------------------------------------------------------------------------------------------
MemRef m_Mem; /* Reference to the associated memory manager. */
};
} // Namespace:: SqMod