firebird-mirror/src/common/classes/alloc.cpp

/*
 *	PROGRAM:	Client/Server Common Code
 *	MODULE:		alloc.cpp
 *	DESCRIPTION:	Memory Pool Manager (based on B+ tree)
 *
 *  The contents of this file are subject to the Initial
 *  Developer's Public License Version 1.0 (the "License");
 *  you may not use this file except in compliance with the
 *  License. You may obtain a copy of the License at
 *  http://www.ibphoenix.com/main.nfs?a=ibphoenix&page=ibp_idpl.
 *
 *  Software distributed under the License is distributed AS IS,
 *  WITHOUT WARRANTY OF ANY KIND, either express or implied.
 *  See the License for the specific language governing rights
 *  and limitations under the License.
 *
 *  The Original Code was created by Nickolay Samofatov
 *  for the Firebird Open Source RDBMS project.
 *
 *  Copyright (c) 2004 Nickolay Samofatov <nickolay@broadviewsoftware.com>
 *  and all contributors signed below.
 *
 *  All Rights Reserved.
 *  Contributor(s): ______________________________________.
 *
 *
 */

/*  PLEASE, DO NOT CONSTIFY THIS MODULE !!! */

#include "firebird.h"
#include "../common/classes/alloc.h"
#include "../common/classes/fb_tls.h"
#include "../jrd/gdsassert.h"
#ifdef HAVE_MMAP
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#endif

#ifdef USE_VALGRIND
#include <valgrind/memcheck.h>
#endif

// Fill blocks with patterns
#define FREE_PATTERN 0xDEADBEEF
#define ALLOC_PATTERN 0xFEEDABED
#ifdef DEBUG_GDS_ALLOC
# define PATTERN_FILL(ptr, size, pattern) for (size_t _i = 0; _i < size / sizeof(unsigned int); _i++) \
	((unsigned int*)(ptr))[_i] = (pattern)
#else
# define PATTERN_FILL(ptr, size, pattern) ((void)0)
#endif

// TODO (in order of importance):
// 1. local pool locking +
// 2. line number debug info +
// 3. debug alloc/free pattern +
// 4. print pool contents function +
//---- Not needed for current codebase
// 5. Pool size limit
// 6. allocation source +
// 7. shared pool locking
// 8. red zones checking (not really needed because verify_pool is able to detect most corruption cases)

/****************************** Local declarations *****************************/

namespace {

using namespace Firebird;

inline static void mem_assert(bool value)
{
	if (!value) abort();
}

// Returns redirect list for given memory block
inline MemoryRedirectList* block_list_small(MemoryBlock* block)
{
    return (MemoryRedirectList*)((char*)block + MEM_ALIGN(sizeof(MemoryBlock)) + 
		block->mbk_small.mbk_length - MEM_ALIGN(sizeof(MemoryRedirectList)));
}

inline MemoryRedirectList* block_list_large(MemoryBlock* block)
{
    return (MemoryRedirectList*)((char*)block + MEM_ALIGN(sizeof(MemoryBlock)) + 
		block->mbk_large_length - MEM_ALIGN(sizeof(MemoryRedirectList)));
}

// Returns block header from user block pointer
inline MemoryBlock* ptrToBlock(void *ptr)
{
    return (MemoryBlock*)((char*)ptr - MEM_ALIGN(sizeof(MemoryBlock)));
}

// Returns user memory pointer for block header pointer
template <typename T>
inline T blockToPtr(MemoryBlock *block)
{
    return reinterpret_cast<T>((char*)block + MEM_ALIGN(sizeof(MemoryBlock)));
}

// Returns previos block in extent. Doesn't check that next block exists
inline MemoryBlock* prev_block(MemoryBlock *block)
{
	return (MemoryBlock*)((char*)block - block->mbk_small.mbk_prev_length - MEM_ALIGN(sizeof(MemoryBlock)));
}

// Returns next block in extent. Doesn't check that previous block exists
inline MemoryBlock* next_block(MemoryBlock *block)
{
	return (MemoryBlock*)((char*)block + block->mbk_small.mbk_length + MEM_ALIGN(sizeof(MemoryBlock)));
}

inline size_t FB_MAX(size_t M, size_t N)
{
	return M > N ? M : N;
}
  
// Size in bytes, must be aligned according to ALLOC_ALIGNMENT
// It should also be a multiply of page size
const size_t EXTENT_SIZE = 65536;
// We cache this amount of extents to avoid memory mapping overhead
const int MAP_CACHE_SIZE = 16; // == 1 MB
// Size of pool to start its own mapping and stop redirecting allocations to parent
// For current implementation it should be smaller then maximum block size which can fit in extent
const size_t REDIRECT_THRESHOLD = 32768;

// Declare thread-specific variable for context memory pool
TLS_DECLARE(MemoryPool*, contextPool);

// Support for memory mapping facilities
#if defined(WIN_NT)
size_t get_page_size()
{
	SYSTEM_INFO info;
	GetSystemInfo(&info);
	return info.dwPageSize;
}
#elif defined(HAVE_MMAP)
size_t get_page_size()
{
	return sysconf(_SC_PAGESIZE);
}
#endif

#if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
# define MAP_ANONYMOUS MAP_ANON
#endif

#if defined(HAVE_MMAP) && !defined(MAP_ANONYMOUS)
int dev_zero_fd = -1; /* Cached file descriptor for /dev/zero. */
#endif

#if defined(WIN_NT) || defined(HAVE_MMAP)
// Extents cache is not used when DEBUG_GDS_ALLOC or USE_VALGRIND is enabled.
// This slows down things a little due to frequent syscalls mapping/unmapping 
// memory but allows to detect more allocation errors
Firebird::Vector<void*, MAP_CACHE_SIZE> extents_cache;
Mutex cache_mutex;

// avoid races during initialization
size_t map_page_size = 0;

inline size_t get_map_page_size()
{
	if (! map_page_size) 
	{
		map_page_size = get_page_size();
	}
	return map_page_size;
}
#endif

#ifdef USE_VALGRIND
// Circular FIFO buffer of read/write protected extents pending free operation
// Race protected via cache_mutex.
struct DelayedExtent {
	void *memory; // Extent pointer
	size_t size;  // Size of extent
	int handle;   // Valgrind handle of protected extent block
};

DelayedExtent delayedExtents[DELAYED_EXTENT_COUNT];
size_t delayedExtentCount = 0;
size_t delayedExtentsPos = 0;
#endif




} // namespace

namespace Firebird {

/****************************** Firebird::MemoryPool ***************************/

static void print_block(FILE *file, MemoryBlock *blk, bool used_only,
	const char* filter_path, const size_t filter_len);

inline void MemoryPool::increment_usage(size_t size)
{
	size_t temp = stats->mst_usage += size;
	if (temp > stats->mst_max_usage)
		stats->mst_max_usage = temp;
	used_memory += size;
}

inline void MemoryPool::decrement_usage(size_t size)
{
	stats->mst_usage -= size;
	used_memory -= size;
}

inline void MemoryPool::increment_mapping(size_t size)
{
	size_t temp = stats->mst_mapped += size;
	if (temp > stats->mst_max_mapped)
		stats->mst_max_mapped = temp;
	mapped_memory += size;
}

inline void MemoryPool::decrement_mapping(size_t size)
{
	stats->mst_mapped -= size;
	mapped_memory -= size;
}

MemoryPool* MemoryPool::setContextPool(MemoryPool* newPool)
{
	MemoryPool* old = TLS_GET(contextPool);
	TLS_SET(contextPool, newPool);
	return old;
}
	
MemoryPool* MemoryPool::getContextPool()
{
	return TLS_GET(contextPool);
}

// Initialize default stats group
MemoryStats* MemoryPool::default_stats_group = 0;

// Initialize process memory pool to avoid possible race conditions.
// At this point also set contextMemoryPool for main thread (or all
// process in case of no threading).
namespace {
	char msBuffer[sizeof(MemoryStats) + ALLOC_ALIGNMENT];
	MemoryPool* createProcessMemoryPool()
	{
		MemoryPool::default_stats_group =
			new((void*)(IPTR) MEM_ALIGN((size_t)(IPTR) msBuffer)) MemoryStats;
		MemoryPool* p = MemoryPool::createPool();
		fb_assert(p);
#ifndef SUPERCLIENT
		MemoryPool::setContextPool(p);
#endif
		return p;
	}
} // anonymous namespace
MemoryPool* MemoryPool::processMemoryPool = createProcessMemoryPool();


void MemoryPool::setStatsGroup(MemoryStats& statsL)
{
	// This locking pattern is necessary to ensure thread-safety of this routine.
	// It is deadlock-free only as long other code takes locks in the same order.
	// There are no other places which need both locks at once so this code seems
	// to be safe
	if (parent) parent->lock.enter();
	lock.enter();
	size_t sav_used_memory = used_memory.value();
	size_t sav_mapped_memory = mapped_memory;
	decrement_mapping(sav_mapped_memory);
	decrement_usage(sav_used_memory);
	this->stats = &statsL;
	increment_mapping(sav_mapped_memory);
	increment_usage(sav_used_memory);	
	lock.leave();
	if (parent) parent->lock.leave();
}

MemoryPool::MemoryPool(MemoryPool* parentL, 
		MemoryStats &statsL, void *first_extent, void *root_page
	) :
	parent_redirect(parentL != NULL),
	freeBlocks((InternalAllocator*)this, root_page),
	extents((MemoryExtent *)first_extent), 
	needSpare(false),
	pendingFree(NULL),
	used_memory(0),
	mapped_memory(0),
	parent(parentL),
	parent_redirected(NULL),
	os_redirected(NULL),
	redirect_amount(0),
	stats(&statsL)
{
}

void MemoryPool::updateSpare()
{
	// Pool does not maintain its own allocation mechanizms if it redirects allocations to parent
	fb_assert(!parent_redirect);
	do {
		// Try to allocate a number of pages to return tree to usable state (when we are able to add blocks safely there)
		// As a result of this operation we may get some extra blocks in pendingFree list
		while (spareLeafs.getCount() < spareLeafs.getCapacity()) {
			void* temp = internal_alloc(MEM_ALIGN(sizeof(FreeBlocksTree::ItemList)), TYPE_LEAFPAGE);
			if (!temp)
				return;
			spareLeafs.add(temp);
		}
		while ( (int) spareNodes.getCount() <= freeBlocks.level ) {
			void* temp = internal_alloc(MEM_ALIGN(sizeof(FreeBlocksTree::NodeList)), TYPE_TREEPAGE);
			if (!temp)
				return;
			spareNodes.add(temp);
		}

		// This check is a temporary debugging aid.
		// bool need_check = pendingFree;
		// if (pendingFree) verify_pool();

		needSpare = false;

		// Great, if we were able to restore free blocks tree operations after critically low
		// memory condition then try to add pending free blocks to our tree
		while (pendingFree) {
			PendingFreeBlock *temp = pendingFree;
			pendingFree = temp->next;
			// Blocks added with tree_deallocate may require merging with nearby ones
			// This is why we do internal_deallocate
			internal_deallocate(temp); // Note that this method may change pendingFree!
			
			if (needSpare)
				break; // New pages were added to tree. Loop again
		}

		// if (need_check) verify_pool();
	} while (needSpare);
}

#ifdef USE_VALGRIND

void* MemoryPool::external_alloc(size_t &size)
{
	// This method is assumed to return NULL in case it cannot alloc
	size = FB_ALIGN(size, get_map_page_size());
	void *result = mmap(NULL, size, PROT_READ | PROT_WRITE, 
		MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	// Let Valgrind forget that block was zero-initialized
	VALGRIND_DISCARD(
		VALGRIND_MAKE_WRITABLE(result, size)
	);
	return result;
}
	
void MemoryPool::external_free(void *blk, size_t &size, bool pool_destroying)
{
	// Set access protection for block to prevent memory from deleted pool being accessed
	int handle = VALGRIND_MAKE_NOACCESS(blk, size);

	size = FB_ALIGN(size, get_map_page_size());

	void* unmapBlockPtr = blk;
	size_t unmapBlockSize = size;

	// Employ extents delayed free logic only when pool is destroying.
	// In normal case all blocks pass through queue of sufficent length by themselves
	if (pool_destroying) {
		// Synchronize delayed free queue using extents mutex
		cache_mutex.enter();

		// Extend circular buffer if possible
		if (delayedExtentCount < FB_NELEM(delayedExtents)) {
			DelayedExtent *item = &delayedExtents[delayedExtentCount];
			item->memory = blk;
			item->size = size;
			item->handle = handle;
			delayedExtentCount++;
			cache_mutex.leave();
			return;
		}

		DelayedExtent *item = &delayedExtents[delayedExtentsPos];

		// Free message associated with old extent in Valgrind
		VALGRIND_DISCARD(item->handle);

		// Set up the block we are going to unmap
		unmapBlockPtr = item->memory;
		unmapBlockSize = item->size;

		// Replace element in circular buffer
		item->memory = blk;
		item->handle = handle;
		item->size = size;

		// Move queue pointer to next element and cycle if needed
		delayedExtentsPos++;
		if (delayedExtentsPos >= FB_NELEM(delayedExtents))
			delayedExtentsPos = 0;

		cache_mutex.leave();
	}
	else {
		// Let Valgrind forget about unmapped block
		VALGRIND_DISCARD(handle);
	}

	if (munmap(unmapBlockPtr, unmapBlockSize))
		system_call_failed::raise("munmap");
}

#else

void* MemoryPool::external_alloc(size_t &size)
{
	// This method is assumed to return NULL in case it cannot alloc
# if !defined(DEBUG_GDS_ALLOC) && (defined(WIN_NT) || defined(HAVE_MMAP))
	if (size == EXTENT_SIZE) {
		cache_mutex.enter();
		void *result = NULL;
		if (extents_cache.getCount()) {
			// Use most recently used object to encourage caching
			result = extents_cache[extents_cache.getCount() - 1];
			extents_cache.shrink(extents_cache.getCount() - 1);
		}
		cache_mutex.leave();
		if (result) {
			return result;
		}
	}
# endif
# if defined WIN_NT
	size = FB_ALIGN(size, get_map_page_size());
	return VirtualAlloc(NULL, size, MEM_COMMIT, 
						PAGE_READWRITE);
# elif defined (HAVE_MMAP) && !defined(SOLARIS)
	size = FB_ALIGN(size, get_map_page_size());
#  ifdef MAP_ANONYMOUS
	return  mmap(NULL, size, PROT_READ | PROT_WRITE, 
				MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
#  else	
	// This code is needed for Solaris 2.6, AFAIK  (only?)
	if (dev_zero_fd < 0)
		dev_zero_fd = open("/dev/zero", O_RDWR);
	return mmap(NULL, size, PROT_READ | PROT_WRITE, 
				MAP_PRIVATE, dev_zero_fd, 0);
#  endif //MAP_ANONYMOUS
# elif  defined(SOLARIS)

// No successful return from mmap()  will  return    the value MAP_FAILED.
//The  symbol  MAP_FAILED  is  defined  in  the header     <sys/mman.h>
//Solaris 2.9 #define MAP_FAILED      ((void *) -1)


	size = FB_ALIGN(size, get_map_page_size());
	void *result = NULL;
#  ifdef MAP_ANONYMOUS
    
	result = mmap(0, size, PROT_READ | PROT_WRITE, 
					MAP_PRIVATE | MAP_ANON , -1, 0);
	if (result == MAP_FAILED) {
		// failure happens!
		return NULL;
	}	
	else {
		return result;	
	}	
#  else	
	// This code is needed for Solaris 2.6, AFAIK
	if (dev_zero_fd < 0)
		dev_zero_fd = open("/dev/zero", O_RDWR);
	result = mmap(NULL, size, PROT_READ | PROT_WRITE, 
					MAP_PRIVATE, dev_zero_fd, 0);
	if (result == MAP_FAILED) {
		return NULL;
	}	
	else {
		return result;	
	}			
#  endif //MAP_ANONYMOUS
# else
	return malloc(size);
# endif
}
	
void MemoryPool::external_free(void *blk, size_t &size, bool pool_destroying) {
# if !defined(DEBUG_GDS_ALLOC) && (defined(WIN_NT) || defined(HAVE_MMAP))
	if (size == EXTENT_SIZE) {
		cache_mutex.enter();
		if (extents_cache.getCount() < extents_cache.getCapacity()) {
			extents_cache.add(blk);
			cache_mutex.leave();
			return;
		}
		cache_mutex.leave();
	}
# endif
# if defined WIN_NT
	size = FB_ALIGN(size, get_map_page_size());
	if (!VirtualFree(blk, 0, MEM_RELEASE))
		system_call_failed::raise("VirtualFree");
# elif defined HAVE_MMAP
	size = FB_ALIGN(size, get_map_page_size());
#  if (defined SOLARIS) && (defined HAVE_CADDR_T)
	if (munmap((caddr_t) blk, size))
		system_call_failed::raise("munmap");

#  else 
	if (munmap(blk, size))
		system_call_failed::raise("munmap");
#  endif /*Solaris*/
# else
	::free(blk);
# endif
}

#endif

void* MemoryPool::tree_alloc(size_t size) {
	if (size == sizeof(FreeBlocksTree::ItemList))
		// This condition is to handle case when nodelist and itemlist have equal size
		if (sizeof(FreeBlocksTree::ItemList) != sizeof(FreeBlocksTree::NodeList) || 
			spareLeafs.getCount()) 
		{
			if (!spareLeafs.getCount())
				Firebird::BadAlloc::raise();
			void *temp = spareLeafs[spareLeafs.getCount() - 1];
			spareLeafs.shrink(spareLeafs.getCount() - 1);
			needSpare = true;
			return temp;
		}
	if (size == sizeof(FreeBlocksTree::NodeList)) {
		if (!spareNodes.getCount())
			Firebird::BadAlloc::raise();
		void *temp = spareNodes[spareNodes.getCount() - 1];
		spareNodes.shrink(spareNodes.getCount() - 1);
		needSpare = true;
		return temp;
	}
	fb_assert(false);
	return NULL;
}

void MemoryPool::tree_free(void* block) {
	// This method doesn't merge nearby pages
	((PendingFreeBlock*)block)->next = pendingFree;
	ptrToBlock(block)->mbk_flags &= ~MBK_USED;
	ptrToBlock(block)->mbk_prev_fragment = NULL;
	pendingFree = (PendingFreeBlock*)block;
	needSpare = true;
}

void* MemoryPool::allocate_nothrow(size_t size, SSHORT type
#ifdef DEBUG_GDS_ALLOC
	, const char* file, int line
#endif
) {
#ifdef USE_VALGRIND
	size_t requested_size = size;
	// First red zone is embedded into block header
	size = MEM_ALIGN(size) + VALGRIND_REDZONE;
#else
	size = MEM_ALIGN(size);
#endif
	// Blocks with internal length of zero make allocator unhappy
	if (!size) size = MEM_ALIGN(1);

	if (parent_redirect) {
		// We do not synchronize redirect_amount here. In the worst case we redirect slightly 
		// more allocations to parent than we wanted. This shouldn't cause problems
		if (redirect_amount + size < REDIRECT_THRESHOLD) {
			parent->lock.enter();
			// Allocate block from parent
			void* result = parent->internal_alloc(size + MEM_ALIGN(sizeof(MemoryRedirectList)), type
#ifdef DEBUG_GDS_ALLOC
			  , file, line
#endif
			);
			if (!result) {
				parent->lock.leave();
				return NULL;
			}
			MemoryBlock* blk = ptrToBlock(result);
			blk->mbk_pool = this;
			blk->mbk_flags |= MBK_PARENT;
			// Add block to the list of redirected blocks
			block_list_small(parent_redirected)->mrl_prev = blk;
			MemoryRedirectList *list = block_list_small(blk);
			list->mrl_prev = NULL;
			list->mrl_next = parent_redirected;
			parent_redirected = blk;

			// Update usage statistics
			size_t blk_size = blk->mbk_small.mbk_length - MEM_ALIGN(sizeof(MemoryRedirectList));
			increment_usage(blk_size);
			redirect_amount += blk_size;
			parent->lock.leave();
#ifdef USE_VALGRIND
			VALGRIND_MEMPOOL_ALLOC(this, result, requested_size);
			//VALGRIND_MAKE_NOACCESS((char*)result - VALGRIND_REDZONE, VALGRIND_REDZONE);
			//VALGRIND_MAKE_WRITABLE(result, requested_size);
			//VALGRIND_MAKE_NOACCESS((char*)result + requested_size, VALGRIND_REDZONE);
#endif
			return result;
		}
		else {
			lock.enter();
			if (parent_redirect) { // It may have changed while we were taking the lock
				parent_redirect = false;
				// Do some hard manual work to initialize first extent
				
				// This is the exact initial layout of memory pool in the first extent //
				// MemoryExtent
				// MemoryBlock
				// FreeBlocksTree::ItemList
				// MemoryBlock
				// free space
				//
				// ******************************************************************* //
				size_t ext_size = EXTENT_SIZE;
				MemoryExtent *extent = (MemoryExtent*)external_alloc(ext_size);
				fb_assert(ext_size == EXTENT_SIZE); // Make sure exent size is a multiply of page size
	
				if (!extent) {
					lock.leave();
					return NULL;
				}
				extent->mxt_next = NULL;
				extent->mxt_prev = NULL;
				extents = extent;
				increment_mapping(EXTENT_SIZE);
		
				MemoryBlock* hdr = (MemoryBlock*) ((char*)extent +
					MEM_ALIGN(sizeof(MemoryExtent)));
				hdr->mbk_pool = this;
				hdr->mbk_flags = MBK_USED;
				hdr->mbk_type = TYPE_LEAFPAGE;
				hdr->mbk_small.mbk_length = MEM_ALIGN(sizeof(FreeBlocksTree::ItemList));
				hdr->mbk_small.mbk_prev_length = 0;
				spareLeafs.add((char*)hdr + MEM_ALIGN(sizeof(MemoryBlock)));
				
				MemoryBlock* blk = (MemoryBlock *)((char*)extent +
					MEM_ALIGN(sizeof(MemoryExtent)) +
					MEM_ALIGN(sizeof(MemoryBlock)) +
					MEM_ALIGN(sizeof(FreeBlocksTree::ItemList)));
				int blockLength = EXTENT_SIZE -
					MEM_ALIGN(sizeof(MemoryExtent)) -
					MEM_ALIGN(sizeof(MemoryBlock)) -
					MEM_ALIGN(sizeof(FreeBlocksTree::ItemList)) -
					MEM_ALIGN(sizeof(MemoryBlock));
				blk->mbk_flags = MBK_LAST;
				blk->mbk_type = 0;
				blk->mbk_small.mbk_length = blockLength;
				blk->mbk_small.mbk_prev_length = hdr->mbk_small.mbk_length;
				blk->mbk_prev_fragment = NULL;
				FreeMemoryBlock *freeBlock = blockToPtr<FreeMemoryBlock*>(blk);
				freeBlock->fbk_next_fragment = NULL;
				BlockInfo temp = {blockLength, freeBlock};
				freeBlocks.add(temp);
				updateSpare();
			}
			lock.leave();
		}
	}

	lock.enter();
	// If block cannot fit into extent then allocate it from OS directly
	if (size > EXTENT_SIZE - MEM_ALIGN(sizeof(MemoryBlock)) - MEM_ALIGN(sizeof(MemoryExtent))) {
		size_t ext_size = MEM_ALIGN(sizeof(MemoryBlock)) + size + 
			MEM_ALIGN(sizeof(MemoryRedirectList));
		MemoryBlock *blk = (MemoryBlock*) external_alloc(ext_size);
		if (!blk) {
			lock.leave();
			return NULL;
		}
		increment_mapping(ext_size);
		blk->mbk_pool = this;
		blk->mbk_flags = MBK_LARGE | MBK_USED;
		blk->mbk_type = type;
		blk->mbk_large_length = size + MEM_ALIGN(sizeof(MemoryRedirectList));
#ifdef DEBUG_GDS_ALLOC
		blk->mbk_file = file;
		blk->mbk_line = line;
#endif
		// Add block to the list of redirected blocks
		if (os_redirected)
			block_list_large(os_redirected)->mrl_prev = blk;
		MemoryRedirectList *list = block_list_large(blk);
		list->mrl_prev = NULL;
		list->mrl_next = os_redirected;
		os_redirected = blk;
		
		// Update usage statistics
		increment_usage(size);
		lock.leave();
		void *result = blockToPtr<void*>(blk);
#ifdef USE_VALGRIND
		VALGRIND_MEMPOOL_ALLOC(this, result, requested_size);
		//VALGRIND_MAKE_NOACCESS((char*)result - VALGRIND_REDZONE, VALGRIND_REDZONE);
		//VALGRIND_MAKE_WRITABLE(result, requested_size);
		//VALGRIND_MAKE_NOACCESS((char*)result + requested_size, VALGRIND_REDZONE);
#endif 
		return result;
	}
	// Otherwise use conventional allocator
	void* result = internal_alloc(size, type
#ifdef DEBUG_GDS_ALLOC
		, file, line
#endif
	);
	// Update usage statistics
	if (result)
		increment_usage(ptrToBlock(result)->mbk_small.mbk_length);
	// Update spare after we increment usage statistics - to allow verify_pool in updateSpare
	if (needSpare)
		updateSpare();
	lock.leave();
#ifdef USE_VALGRIND
	VALGRIND_MEMPOOL_ALLOC(this, result, requested_size);
	//VALGRIND_MAKE_NOACCESS((char*)result - VALGRIND_REDZONE, VALGRIND_REDZONE);
	//VALGRIND_MAKE_WRITABLE(result, requested_size);
	//VALGRIND_MAKE_NOACCESS((char*)result + requested_size, VALGRIND_REDZONE);
#endif 
	return result;
}

void* MemoryPool::allocate(size_t size, SSHORT type
#ifdef DEBUG_GDS_ALLOC
	, const char* file, int line
#endif
) {
	void* result = allocate_nothrow(size, type
#ifdef DEBUG_GDS_ALLOC
		, file, line
#endif
	);
	if (!result)
		Firebird::BadAlloc::raise();
	return result;
}

bool MemoryPool::verify_pool(bool fast_checks_only) {
	lock.enter();
	mem_assert(!pendingFree || needSpare); // needSpare flag should be set if we are in 
										// a critically low memory condition
	size_t blk_used_memory = 0;
	size_t blk_mapped_memory = 0;

	// Verify that free blocks tree is consistent and indeed contains free memory blocks
	if (freeBlocks.getFirst()) 
		do {
			BlockInfo *current = &freeBlocks.current();

			// Verify that head of free blocks list set correctly
			mem_assert(current->bli_fragments);
			mem_assert(ptrToBlock(current->bli_fragments)->mbk_prev_fragment == NULL);
		
			// Look over all blocks in list checking that things look kosher
			for (FreeMemoryBlock *fragment = current->bli_fragments; 
				 fragment; fragment = fragment->fbk_next_fragment)
			{
				// Make sure that list is actually doubly linked
				if (fragment->fbk_next_fragment)
					mem_assert(ptrToBlock(fragment->fbk_next_fragment)->mbk_prev_fragment == fragment);

				MemoryBlock *blk = ptrToBlock(fragment);

				// Check block flags for correctness
				mem_assert(!(blk->mbk_flags & (MBK_LARGE | MBK_PARENT | MBK_USED | MBK_DELAYED)));

				// Check block length
				mem_assert(blk->mbk_small.mbk_length == current->bli_length);
			}
		} while (freeBlocks.getNext());

	// check each block in each segment for consistency with free blocks structure
	for (MemoryExtent *extent = extents; extent; extent = extent->mxt_next) {
		// Verify doubly linked list
		if (extent == extents) {
			mem_assert(extent->mxt_prev == NULL);
		}
		else {
			mem_assert(extent->mxt_prev);
			mem_assert(extent->mxt_prev->mxt_next == extent);
		}
		blk_mapped_memory += EXTENT_SIZE;
		USHORT prev_length = 0;
		for (MemoryBlock *blk = (MemoryBlock *)((char*)extent + MEM_ALIGN(sizeof(MemoryExtent)));
			; 
			blk = next_block(blk))
		{
			// Verify block flags, large blocks are not allowed here
			mem_assert(!(blk->mbk_flags & 
				~(MBK_USED | MBK_LAST | MBK_PARENT | MBK_DELAYED)));

			// Check that if block is marked as delayed free it is still accounted as used
			mem_assert(!(blk->mbk_flags & MBK_DELAYED) || (blk->mbk_flags & MBK_USED));

			// Check pool pointer
			if (blk->mbk_flags & MBK_USED) { // pool is set for used blocks only
				if (blk->mbk_flags & MBK_PARENT)
					mem_assert(blk->mbk_pool->parent == this);
				else
					mem_assert(blk->mbk_pool == this);
			}

			// Calculate memory usage
			if ((blk->mbk_flags & MBK_USED) && !(blk->mbk_flags & MBK_PARENT) && 
				!(blk->mbk_flags & MBK_DELAYED) && (blk->mbk_type >= 0)) 
			{
				blk_used_memory += blk->mbk_small.mbk_length;
			}
			
			mem_assert(blk->mbk_small.mbk_prev_length == prev_length); // Prev is correct ?
			bool foundPending = false;
			for (PendingFreeBlock *tmp = pendingFree; tmp; tmp = tmp->next)
				if (tmp == (PendingFreeBlock *)((char*)blk + MEM_ALIGN(sizeof(MemoryBlock)))) {
					mem_assert(!foundPending); // Block may be in pending list only one time
					foundPending = true;
				}
			bool foundTree = false;
			if (freeBlocks.locate(blk->mbk_small.mbk_length)) {
				// Check previous fragment pointer if block is marked as unused
				if (!(blk->mbk_flags & MBK_USED)) {
					if (blk->mbk_prev_fragment) {
						// See if previous fragment seems kosher
						MemoryBlock *prev_fragment_blk = ptrToBlock(blk->mbk_prev_fragment);
						mem_assert(
							!(prev_fragment_blk->mbk_flags & (MBK_LARGE | MBK_PARENT | MBK_USED | MBK_DELAYED)) &&
							prev_fragment_blk->mbk_small.mbk_length);
					}
					else {
						// This is either the head or the list or block freom pendingFree list
						mem_assert(foundPending || ptrToBlock(freeBlocks.current().bli_fragments) == blk);
					}

					// See if next fragment seems kosher 
					// (note that FreeMemoryBlock has the same structure as PendingFreeBlock so we can do this check)
					FreeMemoryBlock *next_fragment = blockToPtr<FreeMemoryBlock*>(blk)->fbk_next_fragment;
					if (next_fragment) {
						MemoryBlock *next_fragment_blk = ptrToBlock(next_fragment);
						mem_assert(
							!(next_fragment_blk->mbk_flags & (MBK_LARGE | MBK_PARENT | MBK_USED | MBK_DELAYED)) &&
							next_fragment_blk->mbk_small.mbk_length);
					}
				}

				if (fast_checks_only) {
					foundTree = !(blk->mbk_flags & MBK_USED) && 
						(blk->mbk_prev_fragment || ptrToBlock(freeBlocks.current().bli_fragments) == blk);
				} 
				else {
					for (FreeMemoryBlock* freeBlk = freeBlocks.current().bli_fragments; freeBlk; freeBlk = freeBlk->fbk_next_fragment)
						if (ptrToBlock(freeBlk) == blk) {
							mem_assert(!foundTree); // Block may be present in free blocks tree only once
							foundTree = true;
						}
				}
			}
			mem_assert(!(foundTree && foundPending)); // Block shouldn't be present both in
												   // pending list and in tree list
			
			if (!(blk->mbk_flags & MBK_USED)) {
				mem_assert(foundTree || foundPending); // Block is free. Should be somewhere
			}
			else
				mem_assert(!foundTree && !foundPending); // Block is not free. Should not be in free lists
			prev_length = blk->mbk_small.mbk_length;
			if (blk->mbk_flags & MBK_LAST)
				break;
		}
	}
	
	// Verify large blocks
	for (MemoryBlock *large = os_redirected; large; large = block_list_large(large)->mrl_next)
	{
		MemoryRedirectList* list = block_list_large(large);
		// Verify doubly linked list
		if (large == os_redirected) {
			mem_assert(list->mrl_prev == NULL);
		}
		else {
			mem_assert(list->mrl_prev);
			mem_assert(block_list_large(list->mrl_prev)->mrl_next == large);
		}
		mem_assert(large->mbk_flags & MBK_LARGE);
		mem_assert(large->mbk_flags & MBK_USED);
		mem_assert(!(large->mbk_flags & MBK_PARENT));

		if (!(large->mbk_flags & MBK_DELAYED))
			blk_used_memory += large->mbk_large_length - MEM_ALIGN(sizeof(MemoryRedirectList));

#if defined(WIN_NT) || defined(HAVE_MMAP)
		blk_mapped_memory += FB_ALIGN(large->mbk_large_length, get_map_page_size());
#else
		blk_mapped_memory += large->mbk_large_length;
#endif
	}

	// Verify memory fragments in pending free list
	for (PendingFreeBlock* pBlock = pendingFree; pBlock; pBlock = pBlock->next) {
		MemoryBlock *blk = ptrToBlock(pBlock);
		mem_assert(blk->mbk_prev_fragment == NULL);

		// Check block flags for correctness
		mem_assert(!(blk->mbk_flags & (MBK_LARGE | MBK_PARENT | MBK_USED | MBK_DELAYED)));
	}
	
	// Verify memory usage accounting
	mem_assert(blk_mapped_memory == mapped_memory);
	lock.leave();
	
	if (parent) {
		parent->lock.enter();
		// Verify redirected blocks
		size_t blk_redirected = 0;
		for (MemoryBlock *redirected = parent_redirected; redirected; redirected = block_list_small(redirected)->mrl_next)
		{
			MemoryRedirectList* list = block_list_small(redirected);
			// Verify doubly linked list
			if (redirected == parent_redirected) {
				mem_assert(list->mrl_prev == NULL);
			}
			else {
				mem_assert(list->mrl_prev);
				mem_assert(block_list_small(list->mrl_prev)->mrl_next == redirected);
			}
			// Verify flags
			mem_assert(redirected->mbk_flags & MBK_PARENT);
			mem_assert(redirected->mbk_flags & MBK_USED);
			mem_assert(!(redirected->mbk_flags & MBK_LARGE));
			if (redirected->mbk_type >= 0) {
				size_t blk_size = redirected->mbk_small.mbk_length - sizeof(MemoryRedirectList);
				blk_redirected += blk_size;
				if (!(redirected->mbk_flags & MBK_DELAYED))
					blk_used_memory += blk_size;
			}
		}
		// Check accounting
		mem_assert(blk_redirected == redirect_amount);
		mem_assert(blk_used_memory == (size_t) used_memory.value());
		parent->lock.leave();
	}
	else {
		mem_assert(blk_used_memory == (size_t) used_memory.value());
	}
	
	return true;
}

static void print_block(FILE *file, MemoryBlock *blk, bool used_only,
	const char* filter_path, const size_t filter_len)
{
	void *mem = blockToPtr<void*>(blk);
	if (((blk->mbk_flags & MBK_USED) && 
		!(blk->mbk_flags & MBK_DELAYED) && blk->mbk_type >= 0) || !used_only) 
	{
		char flags[100];
		flags[0] = 0;
		if (blk->mbk_flags & MBK_USED)
			strcat(flags, " USED");
		if (blk->mbk_flags & MBK_LAST)
			strcat(flags, " LAST");
		if (blk->mbk_flags & MBK_LARGE)
			strcat(flags, " LARGE");
		if (blk->mbk_flags & MBK_PARENT)
			strcat(flags, " PARENT");
		if (blk->mbk_flags & MBK_DELAYED)
			strcat(flags, " DELAYED");

		int size =
			blk->mbk_flags & MBK_LARGE ? blk->mbk_large_length : blk->mbk_small.mbk_length;
#ifdef DEBUG_GDS_ALLOC
		if (blk->mbk_flags & MBK_USED)
		{
			if (!filter_path || blk->mbk_file
				&& !strncmp(filter_path, blk->mbk_file, filter_len))
			{
				if (blk->mbk_type > 0)
					fprintf(file, "%p%s: size=%d type=%d allocated at %s:%d\n",
						mem, flags, size, blk->mbk_type, blk->mbk_file, blk->mbk_line);
				else if (blk->mbk_type == 0)
					fprintf(file, "%p%s: size=%d allocated at %s:%d\n",
						mem, flags, size, blk->mbk_file, blk->mbk_line);
				else
					fprintf(file, "%p%s: size=%d type=%d\n",
						mem, flags, size, blk->mbk_type);
			}
		}
#else
		if (blk->mbk_type && (blk->mbk_flags & MBK_USED))
			fprintf(file, "%p%s: size=%d type=%d\n",
				mem, flags, size, blk->mbk_type);
#endif
		else
			fprintf(file, "%p%s: size=%d\n",
				mem, flags, size);
	}
}

void MemoryPool::print_contents(const char* filename, bool used_only,
	const char* filter_path)
{
	FILE *out = fopen(filename, "w");
	if (!out)
		return;

	print_contents(out, used_only, filter_path);
	fclose(out);
}

// This member function can't be const because there are calls to the mutex.
void MemoryPool::print_contents(FILE *file, bool used_only,
	const char* filter_path)
{
	lock.enter();
	fprintf(file, "********* Printing contents of pool %p used=%ld mapped=%ld:\n", 
		this, (long)used_memory.value(), (long)mapped_memory);
		
	const size_t filter_len = filter_path ? strlen(filter_path) : 0;
	// Print extents
	for (MemoryExtent *extent = extents; extent; extent = extent->mxt_next) {
		if (!used_only)
			fprintf(file, "EXTENT %p:\n", extent);
		for (MemoryBlock *blk = (MemoryBlock *)((char*)extent + MEM_ALIGN(sizeof(MemoryExtent)));
			; 
			blk = next_block(blk))
		{
			print_block(file, blk, used_only, filter_path, filter_len);
			if (blk->mbk_flags & MBK_LAST)
				break;
		}
	}
	// Print large blocks
	if (os_redirected) {
		fprintf(file, "LARGE BLOCKS:\n");
		for (MemoryBlock *blk = os_redirected; blk; blk = block_list_large(blk)->mrl_next)
			print_block(file, blk, used_only, filter_path, filter_len);
	}
	lock.leave();
	// Print redirected blocks
	if (parent_redirected) {
		fprintf(file, "REDIRECTED TO PARENT %p:\n", parent);
		parent->lock.enter();
		for (MemoryBlock *blk = parent_redirected; blk; blk = block_list_small(blk)->mrl_next)
			print_block(file, blk, used_only, filter_path, filter_len);
		parent->lock.leave();
	}
	fprintf(file, "********* End of output for pool %p.\n", this);
}

MemoryPool* MemoryPool::internal_create(size_t instance_size, MemoryPool* parent, MemoryStats &stats) 
{
	MemoryPool *pool;
#ifndef USE_VALGRIND
	// If pool has a parent things are simplified.
	// Note we do not use parent redirection when using Valgrind because it is 
	// difficult to make memory pass through any delayed free list in this case
	if (parent) {
		parent->lock.enter();
		const size_t size = MEM_ALIGN(instance_size + sizeof(MemoryRedirectList));
		void* mem = parent->internal_alloc(size, TYPE_POOL);
		if (!mem) {
			parent->lock.leave();
			Firebird::BadAlloc::raise();
		}
		pool = new(mem) MemoryPool(parent, stats, NULL, NULL);

		MemoryBlock* blk = ptrToBlock(mem);
		blk->mbk_pool = pool;
		blk->mbk_flags |= MBK_PARENT;
		// Add block to the list of redirected blocks
		MemoryRedirectList *list = block_list_small(blk);
		list->mrl_prev = NULL;
		list->mrl_next = NULL;
		pool->parent_redirected = blk;

		parent->lock.leave();
	} 
	else
#endif
	{

		// This is the exact initial layout of memory pool in the first extent //
		// MemoryExtent
		// MemoryBlock
		// MemoryPool (instance_size)
		// MemoryBlock
		// FreeBlocksTree::ItemList
		// MemoryBlock
		// free space
		//
		// ******************************************************************* //

		size_t ext_size = EXTENT_SIZE;
		char* mem = (char *)external_alloc(ext_size);
		fb_assert(ext_size == EXTENT_SIZE); // Make sure exent size is a multiply of page size
	
		if (!mem)
			Firebird::BadAlloc::raise();
		((MemoryExtent *)mem)->mxt_next = NULL;
		((MemoryExtent *)mem)->mxt_prev = NULL;
		
		pool = new(mem +
			MEM_ALIGN(sizeof(MemoryExtent)) +
			MEM_ALIGN(sizeof(MemoryBlock))) 
		MemoryPool(NULL, stats, mem, mem + 
			MEM_ALIGN(sizeof(MemoryExtent)) + 
			MEM_ALIGN(sizeof(MemoryBlock)) + 
			MEM_ALIGN(instance_size) + 
			MEM_ALIGN(sizeof(MemoryBlock)));
		
		pool->increment_mapping(EXTENT_SIZE);
		
		MemoryBlock *poolBlk = (MemoryBlock*) (mem + MEM_ALIGN(sizeof(MemoryExtent)));
		poolBlk->mbk_pool = pool;
		poolBlk->mbk_flags = MBK_USED;
		poolBlk->mbk_type = TYPE_POOL;
		poolBlk->mbk_small.mbk_length = MEM_ALIGN(instance_size);
		poolBlk->mbk_small.mbk_prev_length = 0;
	
		MemoryBlock* hdr = (MemoryBlock*) (mem +
			MEM_ALIGN(sizeof(MemoryExtent)) +
			MEM_ALIGN(sizeof(MemoryBlock)) +
			MEM_ALIGN(instance_size));
		hdr->mbk_pool = pool;
		hdr->mbk_flags = MBK_USED;
		hdr->mbk_type = TYPE_LEAFPAGE;
		hdr->mbk_small.mbk_length = MEM_ALIGN(sizeof(FreeBlocksTree::ItemList));
		hdr->mbk_small.mbk_prev_length = poolBlk->mbk_small.mbk_length;
		MemoryBlock* blk = (MemoryBlock *)(mem +
			MEM_ALIGN(sizeof(MemoryExtent)) +
			MEM_ALIGN(sizeof(MemoryBlock)) +
			MEM_ALIGN(instance_size) +
			MEM_ALIGN(sizeof(MemoryBlock)) +
			MEM_ALIGN(sizeof(FreeBlocksTree::ItemList)));
		int blockLength = EXTENT_SIZE -
			MEM_ALIGN(sizeof(MemoryExtent)) -
			MEM_ALIGN(sizeof(MemoryBlock)) -
			MEM_ALIGN(instance_size) -
			MEM_ALIGN(sizeof(MemoryBlock)) -
			MEM_ALIGN(sizeof(FreeBlocksTree::ItemList)) -
			MEM_ALIGN(sizeof(MemoryBlock));
		blk->mbk_flags = MBK_LAST;
		blk->mbk_type = 0;
		blk->mbk_small.mbk_length = blockLength;
		blk->mbk_small.mbk_prev_length = hdr->mbk_small.mbk_length;
		blk->mbk_prev_fragment = NULL;
		FreeMemoryBlock *freeBlock = blockToPtr<FreeMemoryBlock*>(blk);
		freeBlock->fbk_next_fragment = NULL;
		BlockInfo temp = {blockLength, freeBlock};
		pool->freeBlocks.add(temp);
		pool->updateSpare();
	}
	
#ifdef USE_VALGRIND
	pool->delayedFreeCount = 0;
	pool->delayedFreePos = 0;
	
	VALGRIND_CREATE_MEMPOOL(pool, VALGRIND_REDZONE, 0);
#endif

	return pool;
}

void MemoryPool::deletePool(MemoryPool* pool)
{
#ifdef USE_VALGRIND
	VALGRIND_DESTROY_MEMPOOL(pool);

	// Do not forget to discard stack traces for delayed free blocks
	for (size_t i = 0; i < pool->delayedFreeCount; i++)
		VALGRIND_DISCARD(pool->delayedFreeHandles[i]);
#endif

	// Adjust usage
	pool->decrement_usage(pool->used_memory.value());
	pool->decrement_mapping(pool->mapped_memory);
	
	// Free mutex
	pool->lock.~Mutex();
	
	// Order of deallocation is of significance because
	// we delete our pool in process
	
	// Deallocate all large blocks redirected to OS
	MemoryBlock *large = pool->os_redirected;
	while (large) {
		MemoryBlock *next = block_list_large(large)->mrl_next;
		size_t ext_size = large->mbk_large_length;
		external_free(large, ext_size, true);
		large = next;
	}
	
	MemoryPool *parent = pool->parent;
	
	// Delete all extents now
	MemoryExtent *extent = pool->extents;
	while (extent) {
		MemoryExtent *next = extent->mxt_next;
		size_t ext_size = EXTENT_SIZE;
		external_free(extent, ext_size, true);
		fb_assert(ext_size == EXTENT_SIZE); // Make sure exent size is a multiply of page size	
		extent = next;
	}
	
	// Deallocate blocks redirected to parent
	// IF parent is set then pool was allocated from it and is not deleted at this point yet
	if (parent) {		
		parent->lock.enter();
		MemoryBlock *redirected = pool->parent_redirected;
		while (redirected) {
			MemoryBlock *next = block_list_small(redirected)->mrl_next;
			redirected->mbk_pool = parent;
			redirected->mbk_flags &= ~MBK_PARENT;
#ifdef USE_VALGRIND
			// Clear delayed bit which may be set here
			redirected->mbk_flags &= ~MBK_DELAYED;

			// Remove protection from red zones of memory block or block as whole if it is
			// in delayed free queue. Since this code makes pointers to deallocated memory
			// immediately valid we disable parent redirection in USE_VALGRIND mode. Code is 
			// here for case if you want to debug something with parent redirection enabled.
			VALGRIND_DISCARD(
				VALGRIND_MAKE_WRITABLE((char*)redirected + MEM_ALIGN(sizeof(MemoryBlock)) - VALGRIND_REDZONE, 
					(redirected->mbk_flags & MBK_LARGE ? redirected->mbk_large_length: redirected->mbk_small.mbk_length) -
					(redirected->mbk_flags & (MBK_LARGE | MBK_PARENT) ? MEM_ALIGN(sizeof(MemoryRedirectList)) : 0) +
					VALGRIND_REDZONE)
			);
#endif
			parent->internal_deallocate((char*)redirected + MEM_ALIGN(sizeof(MemoryBlock)));
			redirected = next;
		}
		// Our pool does not exist at this point
		if (parent->needSpare)
			parent->updateSpare();
		parent->lock.leave();
	}
}

void* MemoryPool::internal_alloc(size_t size, SSHORT type
#ifdef DEBUG_GDS_ALLOC
	, const char* file, int line
#endif
) {
	// This method assumes already aligned block sizes
	fb_assert(size % ALLOC_ALIGNMENT == 0);
	// Make sure block can fit into extent
	fb_assert(size < EXTENT_SIZE - MEM_ALIGN(sizeof(MemoryBlock)) - MEM_ALIGN(sizeof(MemoryExtent)));
	
	// Lookup a block greater or equal than size in freeBlocks tree
	MemoryBlock* blk;
	if (freeBlocks.locate(locGreatEqual, size)) {
		// Found large enough block
		BlockInfo* current = &freeBlocks.current();
		if (current->bli_length - size < MEM_ALIGN(sizeof(MemoryBlock)) + ALLOC_ALIGNMENT)
		{
			blk = ptrToBlock(current->bli_fragments);
			// Block is small enough to be returned AS IS
			blk->mbk_pool = this;
			blk->mbk_flags |= MBK_USED;
			blk->mbk_type = type;
#ifdef DEBUG_GDS_ALLOC
			blk->mbk_file = file;
			blk->mbk_line = line;
#endif
			FreeMemoryBlock *next_free = current->bli_fragments->fbk_next_fragment;
			if (next_free) {
				ptrToBlock(next_free)->mbk_prev_fragment = NULL;
				current->bli_fragments = next_free;
			}
			else
				freeBlocks.fastRemove();
		}
		else {
			// Cut a piece at the end of block in hope to avoid structural
			// modification of free blocks tree
			MemoryBlock *current_block = ptrToBlock(current->bli_fragments);
			current_block->mbk_small.mbk_length -= MEM_ALIGN(sizeof(MemoryBlock)) + size;
			blk = next_block(current_block);
			blk->mbk_pool = this;
			blk->mbk_flags = MBK_USED | (current_block->mbk_flags & MBK_LAST);
#ifdef DEBUG_GDS_ALLOC
			blk->mbk_file = file;
			blk->mbk_line = line;
#endif
			current_block->mbk_flags &= ~MBK_LAST;
			blk->mbk_type = type;
			blk->mbk_small.mbk_length = size;
			blk->mbk_small.mbk_prev_length = current_block->mbk_small.mbk_length;
			if (!(blk->mbk_flags & MBK_LAST))
				next_block(blk)->mbk_small.mbk_prev_length = blk->mbk_small.mbk_length;

			FreeMemoryBlock *next_free = current->bli_fragments->fbk_next_fragment;

			if (next_free) {
				// Moderately cheap case. Quite possibly we only need to tweak doubly 
				// linked lists a little
				ptrToBlock(next_free)->mbk_prev_fragment = NULL;
				current->bli_fragments = next_free;
				addFreeBlock(current_block);
			} 
			else {
				// This is special handling of case when we have single large fragment and
				// cut off small pieces from it. This is common and we avoid modification 
				// of free blocks tree in this case.
				bool get_prev_succeeded = freeBlocks.getPrev();
				if (!get_prev_succeeded || freeBlocks.current().bli_length < current_block->mbk_small.mbk_length) {
					current->bli_length = current_block->mbk_small.mbk_length;
				} 
				else {
					// Moderately expensive case. We need to modify tree for sure
					if (get_prev_succeeded) {
						// Recover tree position after failed shortcut attempt
#ifndef DEV_BUILD
						freeBlocks.getNext();
#else
						bool res = freeBlocks.getNext();
						fb_assert(res);
						fb_assert(&freeBlocks.current() == current);
#endif
					}
					freeBlocks.fastRemove();
					addFreeBlock(current_block);
				}
			}
		}
	}
	else {
		// If we are in a critically low memory condition look up for a block in a list
		// of pending free blocks. We do not do "best fit" in this case
		PendingFreeBlock *itr = pendingFree, *prev = NULL;
		while (itr) {
			MemoryBlock *temp = ptrToBlock(itr);
			if (temp->mbk_small.mbk_length >= size) {
				if (temp->mbk_small.mbk_length - size < MEM_ALIGN(sizeof(MemoryBlock)) + ALLOC_ALIGNMENT)
				{
					// Block is small enough to be returned AS IS
					temp->mbk_flags |= MBK_USED;
					temp->mbk_type = type;
					temp->mbk_pool = this;
#ifdef DEBUG_GDS_ALLOC
					temp->mbk_file = file;
					temp->mbk_line = line;
#endif
					// Remove block from linked list
					if (prev)
						prev->next = itr->next;
					else
						pendingFree = itr->next;						
					PATTERN_FILL(itr, size, ALLOC_PATTERN);
					return itr;
				}
				else {
					// Cut a piece at the end of block
					// We don't need to modify tree of free blocks or a list of
					// pending free blocks in this case
					temp->mbk_small.mbk_length -= MEM_ALIGN(sizeof(MemoryBlock)) + size;
					blk = next_block(temp);
					blk->mbk_pool = this;
					blk->mbk_flags = MBK_USED | (temp->mbk_flags & MBK_LAST);
#ifdef DEBUG_GDS_ALLOC
					blk->mbk_file = file;
					blk->mbk_line = line;
#endif
					temp->mbk_flags &= ~MBK_LAST;
					blk->mbk_type = type;
					blk->mbk_small.mbk_length = size;
					blk->mbk_small.mbk_prev_length = temp->mbk_small.mbk_length;
					if (!(blk->mbk_flags & MBK_LAST))
						next_block(blk)->mbk_small.mbk_prev_length = blk->mbk_small.mbk_length;
					void *result = blockToPtr<void*>(blk);
					PATTERN_FILL(result, size, ALLOC_PATTERN);
					return result;
				}
			}
			prev = itr;
			itr = itr->next;
		}
		// No large enough block found. We need to extend the pool
		size_t ext_size = EXTENT_SIZE;
		MemoryExtent* extent = (MemoryExtent *)external_alloc(ext_size);
		fb_assert(ext_size == EXTENT_SIZE); // Make sure exent size is a multiply of page size
	
		if (!extent) {
			return NULL;
		}
		increment_mapping(EXTENT_SIZE);
		// Add extent to a doubly linked list
		extents->mxt_prev = extent;
		extent->mxt_next = extents;
		extent->mxt_prev = NULL;
		extents = extent;
			
		blk = (MemoryBlock *)((char*)extent + MEM_ALIGN(sizeof(MemoryExtent)));
		blk->mbk_pool = this;
		blk->mbk_flags = MBK_USED;
		blk->mbk_type = type;
#ifdef DEBUG_GDS_ALLOC
		blk->mbk_file = file;
		blk->mbk_line = line;
#endif
		blk->mbk_small.mbk_prev_length = 0;
		if (EXTENT_SIZE - size - MEM_ALIGN(sizeof(MemoryExtent)) - MEM_ALIGN(sizeof(MemoryBlock)) 
					< MEM_ALIGN(sizeof(MemoryBlock)) + ALLOC_ALIGNMENT) 
		{
			// Block is small enough to be returned AS IS
			blk->mbk_flags |= MBK_LAST;
			blk->mbk_small.mbk_length = EXTENT_SIZE - MEM_ALIGN(sizeof(MemoryExtent)) - MEM_ALIGN(sizeof(MemoryBlock));
		}
		else {
			// Cut a piece at the beginning of the block
			blk->mbk_small.mbk_length = size;
			// Put the rest to the tree of free blocks
			MemoryBlock *rest = next_block(blk);
			// Will be initialized (to NULL) by addFreeBlock code
			// rest->mbk_pool = this;
			rest->mbk_flags = MBK_LAST;
			rest->mbk_small.mbk_length = EXTENT_SIZE - MEM_ALIGN(sizeof(MemoryExtent)) - 
				MEM_ALIGN(sizeof(MemoryBlock)) - size - MEM_ALIGN(sizeof(MemoryBlock));
			rest->mbk_small.mbk_prev_length = blk->mbk_small.mbk_length;
			addFreeBlock(rest);
		}
	}
	void *result = blockToPtr<void*>(blk);
	PATTERN_FILL(result, size, ALLOC_PATTERN);
	return result;
}

inline void MemoryPool::addFreeBlock(MemoryBlock *blk)
{
	FreeMemoryBlock* fragmentToAdd = blockToPtr<FreeMemoryBlock*>(blk);
	blk->mbk_prev_fragment = NULL;

	// Cheap case. No modification of tree required
	if (freeBlocks.locate(blk->mbk_small.mbk_length)) {
		BlockInfo *current = &freeBlocks.current();

		// Make new block a head of free blocks doubly linked list
		fragmentToAdd->fbk_next_fragment = current->bli_fragments;
		ptrToBlock(current->bli_fragments)->mbk_prev_fragment = fragmentToAdd;
		current->bli_fragments = fragmentToAdd;
		return;
	}

	// More expensive case. Need to add item to the tree
	fragmentToAdd->fbk_next_fragment = NULL;
	BlockInfo info = {blk->mbk_small.mbk_length, fragmentToAdd};
	try {
		freeBlocks.add(info);
	}
	catch (const Firebird::Exception&) {
		// Add item to the list of pending free blocks in case of critically-low memory condition
		PendingFreeBlock* temp = blockToPtr<PendingFreeBlock*>(blk);
		temp->next = pendingFree;
		pendingFree = temp;
		// NOTE! Items placed into pendingFree queue have mbk_prev_fragment equal to ZERO.
	}
}
		
void MemoryPool::removeFreeBlock(MemoryBlock *blk)
{
	// NOTE! We signal items placed into pendingFree queue via setting their 
	// mbk_prev_fragment to ZERO.

	FreeMemoryBlock *fragmentToRemove = blockToPtr<FreeMemoryBlock*>(blk);
	FreeMemoryBlock *prev = blk->mbk_prev_fragment;
	FreeMemoryBlock *next = fragmentToRemove->fbk_next_fragment;
	if (prev) {
		// Cheapest case. There is no need to touch B+ tree at all.
		// Simply remove item from a middle or end of doubly linked list		
		prev->fbk_next_fragment = next;
		if (next)
			ptrToBlock(next)->mbk_prev_fragment = prev;
		return;
	}

	// Need to locate item in tree
	BlockInfo* current;
	if (freeBlocks.locate(blk->mbk_small.mbk_length) && 
		(current = &freeBlocks.current())->bli_fragments == fragmentToRemove) 
	{
		if (next) {
			// Still moderately fast case. All we need is to replace the head of fragments list
			ptrToBlock(next)->mbk_prev_fragment = NULL;
			current->bli_fragments = next;
		}
		else {
			// Have to remove item from the tree
			freeBlocks.fastRemove();
		}
	}
	else {
		// Our block could be in the pending free blocks list if we are in a 
		// critically-low memory condition or if tree_free placed it there. 
		// Find and remove it from there.
		PendingFreeBlock *itr = pendingFree, 
			*temp = blockToPtr<PendingFreeBlock*>(blk);
		if (itr == temp)
			pendingFree = itr->next;
		else
		{
			while ( itr ) {
				PendingFreeBlock *next2 = itr->next;
				if (next2 == temp) {
					itr->next = temp->next;
					break;
				}
				itr = next2;
			}
			fb_assert(itr); // We had to find it somewhere
		}
	}
}

void MemoryPool::free_blk_extent(MemoryBlock *blk)
{
	MemoryExtent *extent = (MemoryExtent *)((char *)blk - MEM_ALIGN(sizeof(MemoryExtent)));
	
	// Delete extent from the doubly linked list
	if (extent->mxt_prev)
		extent->mxt_prev->mxt_next = extent->mxt_next;
	else
		extents = extent->mxt_next;
	if (extent->mxt_next)
		extent->mxt_next->mxt_prev = extent->mxt_prev;

	fb_assert(blk->mbk_small.mbk_length + MEM_ALIGN(sizeof(MemoryBlock)) + 
		MEM_ALIGN(sizeof(MemoryExtent)) == EXTENT_SIZE);

	size_t ext_size = EXTENT_SIZE;
	external_free(extent, ext_size, false);
	fb_assert(ext_size == EXTENT_SIZE); // Make sure exent size is a multiply of page size	
	decrement_mapping(EXTENT_SIZE);
}

void MemoryPool::internal_deallocate(void *block)
{
	MemoryBlock *blk = ptrToBlock(block);
	
	// This method is normally called for used blocks from our pool. Also it may
	// be called for free blocks in pendingFree list by updateSpare routine. 
	// Such blocks must have mbk_prev_fragment equal to NULL.

	fb_assert(
		blk->mbk_flags & MBK_USED ? 
			blk->mbk_pool == this :
			blk->mbk_prev_fragment == NULL);

	MemoryBlock *prev;
	// Try to merge block with preceding free block
	if (blk->mbk_small.mbk_prev_length && !((prev = prev_block(blk))->mbk_flags & MBK_USED))
	{
	   	removeFreeBlock(prev);
		prev->mbk_small.mbk_length += blk->mbk_small.mbk_length + MEM_ALIGN(sizeof(MemoryBlock));

		MemoryBlock *next = NULL;
		if (blk->mbk_flags & MBK_LAST) {
			prev->mbk_flags |= MBK_LAST;
		}
		else {
			next = next_block(blk);
			if (next->mbk_flags & MBK_USED) {
				next->mbk_small.mbk_prev_length = prev->mbk_small.mbk_length;
				prev->mbk_flags &= ~MBK_LAST;
			}
			else {
				// Merge next block too
				removeFreeBlock(next);
				prev->mbk_small.mbk_length += next->mbk_small.mbk_length + MEM_ALIGN(sizeof(MemoryBlock));
				prev->mbk_flags |= next->mbk_flags & MBK_LAST;
				if (!(next->mbk_flags & MBK_LAST))
					next_block(next)->mbk_small.mbk_prev_length = prev->mbk_small.mbk_length;
			}
		}
		PATTERN_FILL((char*)prev + MEM_ALIGN(sizeof(MemoryBlock)), prev->mbk_small.mbk_length, FREE_PATTERN);
		if (!prev->mbk_small.mbk_prev_length && (prev->mbk_flags & MBK_LAST))
			free_blk_extent(prev);
		else
			addFreeBlock(prev);
	}
	else {
		MemoryBlock *next;
		// Mark block as free
		blk->mbk_flags &= ~MBK_USED;
		// Try to merge block with next free block
		if (!(blk->mbk_flags & MBK_LAST) && 
			!((next = next_block(blk))->mbk_flags & MBK_USED)) 
		{
			removeFreeBlock(next);
			blk->mbk_small.mbk_length += next->mbk_small.mbk_length + MEM_ALIGN(sizeof(MemoryBlock));
			blk->mbk_flags |= next->mbk_flags & MBK_LAST;
			if (!(next->mbk_flags & MBK_LAST))
				next_block(next)->mbk_small.mbk_prev_length = blk->mbk_small.mbk_length;
		}
		PATTERN_FILL(block, blk->mbk_small.mbk_length, FREE_PATTERN);
		if (!blk->mbk_small.mbk_prev_length && (blk->mbk_flags & MBK_LAST))
			free_blk_extent(blk);
		else
			addFreeBlock(blk);
	}
}


void MemoryPool::deallocate(void *block)
{
	if (!block)
		return;

	MemoryBlock* blk = ptrToBlock(block);
	
	fb_assert(blk->mbk_flags & MBK_USED);
	fb_assert(blk->mbk_pool == this);


#ifdef USE_VALGRIND
	// Synchronize delayed free queue using pool mutex
	lock.enter();

	// Memory usage accounting. Do it before Valgrind delayed queue management
	size_t blk_size;
	if (blk->mbk_flags & MBK_LARGE)
		blk_size = blk->mbk_large_length - MEM_ALIGN(sizeof(MemoryRedirectList));
	else {
		blk_size = blk->mbk_small.mbk_length;
		if (blk->mbk_flags & MBK_PARENT)
			blk_size -= MEM_ALIGN(sizeof(MemoryRedirectList));
	}
	decrement_usage(blk_size);

	// Mark block as delayed free in its header
	blk->mbk_flags |= MBK_DELAYED;

	// Notify Valgrind that block is freed from the pool
	VALGRIND_MEMPOOL_FREE(this, block);

	// Make it read and write protected
	int handle = 
		VALGRIND_MAKE_NOACCESS((char*)block - VALGRIND_REDZONE, 
			(blk->mbk_flags & MBK_LARGE ? blk->mbk_large_length: blk->mbk_small.mbk_length) -
			(blk->mbk_flags & (MBK_LARGE | MBK_PARENT) ? MEM_ALIGN(sizeof(MemoryRedirectList)) : 0) +
			VALGRIND_REDZONE);
	
	// Extend circular buffer if possible
	if (delayedFreeCount < FB_NELEM(delayedFree)) {
		delayedFree[delayedFreeCount] = block;
		delayedFreeHandles[delayedFreeCount] = handle;
		delayedFreeCount++;
		lock.leave();
		return;
	}

	// Shift circular buffer pushing out oldest item
	void* requested_block = block;

	block = delayedFree[delayedFreePos];
	blk = ptrToBlock(block);

	// Unmark block as delayed free in its header
	blk->mbk_flags &= ~MBK_DELAYED;

	// Free message associated with block in Valgrind
	VALGRIND_DISCARD(delayedFreeHandles[delayedFreePos]);

	// Remove protection from memory block
	VALGRIND_DISCARD(
		VALGRIND_MAKE_WRITABLE((char*)block - VALGRIND_REDZONE, 
			(blk->mbk_flags & MBK_LARGE ? blk->mbk_large_length: blk->mbk_small.mbk_length) -
			(blk->mbk_flags & (MBK_LARGE | MBK_PARENT) ? MEM_ALIGN(sizeof(MemoryRedirectList)) : 0) +
			VALGRIND_REDZONE)
	);

	// Replace element in circular buffer
	delayedFree[delayedFreePos] = requested_block;
	delayedFreeHandles[delayedFreePos] = handle;

	// Move queue pointer to next element and cycle if needed
	delayedFreePos++;
	if (delayedFreePos >= FB_NELEM(delayedFree))
		delayedFreePos = 0;

	lock.leave();
#endif

	if (blk->mbk_flags & MBK_PARENT) {
		parent->lock.enter();
		blk->mbk_pool = parent;
		blk->mbk_flags &= ~MBK_PARENT;
		// Delete block from list of redirected blocks
		MemoryRedirectList* list = block_list_small(blk);
		if (list->mrl_prev)
			block_list_small(list->mrl_prev)->mrl_next = list->mrl_next;
		else
			parent_redirected = list->mrl_next;
		if (list->mrl_next)
			block_list_small(list->mrl_next)->mrl_prev = list->mrl_prev;
		// Update usage statistics
		size_t size = blk->mbk_small.mbk_length - MEM_ALIGN(sizeof(MemoryRedirectList));
		redirect_amount -= size;
#ifndef USE_VALGRIND
		decrement_usage(size);
#endif
		// Free block from parent
		parent->internal_deallocate(block);
		if (parent->needSpare)
			parent->updateSpare();
		parent->lock.leave();
		return;
	}

	lock.enter();
	
	if (blk->mbk_flags & MBK_LARGE) {
		// Delete block from list of redirected blocks
		MemoryRedirectList *list = block_list_large(blk);
		if (list->mrl_prev)
			block_list_large(list->mrl_prev)->mrl_next = list->mrl_next;
		else
			os_redirected = list->mrl_next;
		if (list->mrl_next)
			block_list_large(list->mrl_next)->mrl_prev = list->mrl_prev;
		// Update usage statistics
		size_t size = blk->mbk_large_length - MEM_ALIGN(sizeof(MemoryRedirectList));
#ifndef USE_VALGRIND
		decrement_usage(size);
#endif
		// Free the block
		size_t ext_size = MEM_ALIGN(sizeof(MemoryBlock)) + size +
			MEM_ALIGN(sizeof(MemoryRedirectList));
		external_free(blk, ext_size, false);
		decrement_mapping(ext_size);
		lock.leave();
		return;
	}
	
	// Deallocate small block from this pool
#ifndef USE_VALGRIND
	decrement_usage(blk->mbk_small.mbk_length);
#endif
	internal_deallocate(block);
	if (needSpare)
		updateSpare();
	
	lock.leave();
}

MemoryPool& AutoStorage::getAutoMemoryPool() { 
#ifndef SUPERCLIENT
	MemoryPool* p = MemoryPool::getContextPool();
#ifdef EMBEDDED
	if (! p)
	{
		p = getDefaultMemoryPool();
	}
#endif //EMBEDDED
#else //SUPERCLIENT
	MemoryPool* p = getDefaultMemoryPool();
#endif //SUPERCLIENT
	fb_assert(p);
	return *p; 
}

#if defined(DEV_BUILD)
void AutoStorage::ProbeStack() const {
	//
	// AutoStorage() default constructor can be used only 
	// for objects on the stack. ProbeStack() uses the 
	// following assumptions to check it:
	//	1. One and only one stack is used for all kind of variables.
	//	2. Objects don't grow > 64K.
	//
	char ProbeVar = '\0';
	const char *MyStack = &ProbeVar;
	const char *ThisLocation = (const char *)this;
	ptrdiff_t distance = ThisLocation - MyStack;
	if (distance < 0) {
		distance = -distance;
	}
	fb_assert(distance < 64 * 1024);
}
#endif

} // namespace Firebird