18 files changed, 1342 insertions, 57 deletions

diff --git a/indra/llcommon/llmemory.cpp b/indra/llcommon/llmemory.cpp
index a502d1a7eb..ca06589611 100644
--- a/indra/llcommon/llmemory.cpp
+++ b/indra/llcommon/llmemory.cpp
@@ -26,8 +26,9 @@
 
 #include "linden_common.h"
 
+#include "llthread.h"
 #if defined(LL_WINDOWS)
-# include <windows.h>
+//# include <windows.h>
 # include <psapi.h>
 #elif defined(LL_DARWIN)
 # include <sys/types.h>
@@ -38,11 +39,19 @@
 #endif
 
 #include "llmemory.h"
+#include "llsys.h"
+
 
 //----------------------------------------------------------------------------
 
 //static
 char* LLMemory::reserveMem = 0;
+U32 LLMemory::sAvailPhysicalMemInKB = U32_MAX ;
+U32 LLMemory::sMaxPhysicalMemInKB = 0;
+U32 LLMemory::sAllocatedMemInKB = 0;
+U32 LLMemory::sAllocatedPageSizeInKB = 0 ;
+U32 LLMemory::sMaxHeapSizeInKB = U32_MAX ;
+BOOL LLMemory::sEnableMemoryFailurePrevention = FALSE;
 
 //static
 void LLMemory::initClass()
@@ -67,6 +76,131 @@ void LLMemory::freeReserve()
 	reserveMem = NULL;
 }
 
+//static 
+void LLMemory::initMaxHeapSizeGB(F32 max_heap_size_gb, BOOL prevent_heap_failure)
+{
+	sMaxHeapSizeInKB = (U32)(max_heap_size_gb * 1024 * 1024) ;
+	sEnableMemoryFailurePrevention = prevent_heap_failure ;
+}
+
+//static 
+void LLMemory::updateMemoryInfo() 
+{
+#if LL_WINDOWS	
+	HANDLE self = GetCurrentProcess();
+	PROCESS_MEMORY_COUNTERS counters;
+	
+	if (!GetProcessMemoryInfo(self, &counters, sizeof(counters)))
+	{
+		llwarns << "GetProcessMemoryInfo failed" << llendl;
+		return ;
+	}
+
+	sAllocatedMemInKB = (U32)(counters.WorkingSetSize / 1024) ;
+	sAllocatedPageSizeInKB = (U32)(counters.PagefileUsage / 1024) ;
+	sMaxPhysicalMemInKB = llmin(LLMemoryInfo::getAvailableMemoryKB() + sAllocatedMemInKB, sMaxHeapSizeInKB);
+
+	if(sMaxPhysicalMemInKB > sAllocatedMemInKB)
+	{
+		sAvailPhysicalMemInKB = sMaxPhysicalMemInKB - sAllocatedMemInKB ;
+	}
+	else
+	{
+		sAvailPhysicalMemInKB = 0 ;
+	}
+#else
+	//not valid for other systems for now.
+	sAllocatedMemInKB = (U32)(LLMemory::getCurrentRSS() / 1024) ;
+	sMaxPhysicalMemInKB = U32_MAX ;
+	sAvailPhysicalMemInKB = U32_MAX ;
+#endif
+
+	return ;
+}
+
+//
+//this function is to test if there is enough space with the size in the virtual address space.
+//it does not do any real allocation
+//if success, it returns the address where the memory chunk can fit in;
+//otherwise it returns NULL.
+//
+//static 
+void* LLMemory::tryToAlloc(void* address, U32 size)
+{
+#if LL_WINDOWS
+	address = VirtualAlloc(address, size, MEM_RESERVE | MEM_TOP_DOWN, PAGE_NOACCESS) ;
+	if(address)
+	{
+		if(!VirtualFree(address, 0, MEM_RELEASE))
+		{
+			llerrs << "error happens when free some memory reservation." << llendl ;
+		}
+	}
+#else
+#endif
+
+	return address ;
+}
+
+//static 
+void LLMemory::logMemoryInfo(BOOL update)
+{
+	if(update)
+	{
+		updateMemoryInfo() ;
+	}
+
+	llinfos << "Current allocated physical memory(KB): " << sAllocatedMemInKB << llendl ;
+	llinfos << "Current allocated page size (KB): " << sAllocatedPageSizeInKB << llendl ;
+	llinfos << "Current availabe physical memory(KB): " << sAvailPhysicalMemInKB << llendl ;
+	llinfos << "Current max usable memory(KB): " << sMaxPhysicalMemInKB << llendl ;
+}
+
+//return 0: everything is normal;
+//return 1: the memory pool is low, but not in danger;
+//return -1: the memory pool is in danger, is about to crash.
+//static 
+S32 LLMemory::isMemoryPoolLow()
+{
+	static const U32 LOW_MEMEOY_POOL_THRESHOLD_KB = 64 * 1024 ; //64 MB for emergency use
+
+	if(!sEnableMemoryFailurePrevention)
+	{
+		return 0 ; //no memory failure prevention.
+	}
+
+	if(sAvailPhysicalMemInKB < (LOW_MEMEOY_POOL_THRESHOLD_KB >> 2)) //out of physical memory
+	{
+		return -1 ;
+	}
+
+	if(sAllocatedPageSizeInKB + (LOW_MEMEOY_POOL_THRESHOLD_KB >> 2) > sMaxHeapSizeInKB) //out of virtual address space.
+	{
+		return -1 ;
+	}
+
+	return (S32)(sAvailPhysicalMemInKB < LOW_MEMEOY_POOL_THRESHOLD_KB || 
+		sAllocatedPageSizeInKB + LOW_MEMEOY_POOL_THRESHOLD_KB > sMaxHeapSizeInKB) ;
+}
+
+//static 
+U32 LLMemory::getAvailableMemKB() 
+{
+	return sAvailPhysicalMemInKB ;
+}
+
+//static 
+U32 LLMemory::getMaxMemKB() 
+{
+	return sMaxPhysicalMemInKB ;
+}
+
+//static 
+U32 LLMemory::getAllocatedMemKB() 
+{
+	return sAllocatedMemInKB ;
+}
+
 void* ll_allocate (size_t size)
 {
 	if (size == 0)
@@ -221,3 +355,822 @@ U64 LLMemory::getCurrentRSS()
 }
 
 #endif
+
+//-------------------------------------------------------------
+//class LLPrivateMemoryPool::LLMemoryBlock
+//-------------------------------------------------------------
+//
+//each memory block could fit for two page sizes: 0.75 * mSlotSize, which starts from the beginning of the memory chunk and grow towards the end of the
+//the block; another is mSlotSize, which starts from the end of the block and grows towards the beginning of the block.
+//
+LLPrivateMemoryPool::LLMemoryBlock::LLMemoryBlock()
+{
+	//empty
+}
+		
+LLPrivateMemoryPool::LLMemoryBlock::~LLMemoryBlock() 
+{
+	//empty
+}
+
+void LLPrivateMemoryPool::LLMemoryBlock::init(char* buffer, U32 buffer_size, U32 slot_size)
+{
+	mBuffer = buffer ;
+	mBufferSize = buffer_size ;
+	mSlotSize = slot_size ;
+	mTotalSlots = buffer_size / mSlotSize ;	
+	llassert_always(mTotalSlots < 256) ; //max number is 256
+	mAllocatedSlots = 0 ;
+
+	//mark free bits
+	S32 usage_bit_len = (mTotalSlots + 31) / 32 ;
+	mDummySize = usage_bit_len - 1 ;
+	if(mDummySize > 0) //extra space to store mUsageBits
+	{
+		mTotalSlots -= (mDummySize * sizeof(mUsageBits) + mSlotSize - 1) / mSlotSize ;
+		usage_bit_len = (mTotalSlots + 31) / 32 ;
+		mDummySize = usage_bit_len - 1 ;
+
+		if(mDummySize > 0)
+		{
+			mUsageBits = 0 ;
+			for(S32 i = 0 ; i < mDummySize ; i++)
+			{
+				*((U32*)mBuffer + i) = 0 ;
+			}
+			if(mTotalSlots & 31)
+			{
+				*((U32*)mBuffer + mDummySize - 1) = (0xffffffff << (mTotalSlots & 31)) ;
+			}
+		}
+	}
+	
+	if(mDummySize < 1)
+	{
+		mUsageBits = 0 ;
+		if(mTotalSlots & 31)
+		{
+			mUsageBits = (0xffffffff << (mTotalSlots & 31)) ;
+		}
+	}
+
+	mSelf = NULL ;
+	mNext = NULL ;
+}
+
+void LLPrivateMemoryPool::LLMemoryBlock::setBuffer(char* buffer, U32 buffer_size)
+{
+	mBuffer = buffer ;
+	mBufferSize = buffer_size ;
+	mTotalSlots = 0 ; //set the block is free.
+}
+
+char* LLPrivateMemoryPool::LLMemoryBlock::allocate() 
+{
+	llassert_always(mAllocatedSlots < mTotalSlots) ;
+	
+	//find a free slot
+	U32* bits = NULL ;
+	U32  k = 0 ;
+	if(mUsageBits != 0xffffffff)
+	{
+		bits = &mUsageBits ;
+	}
+	else if(mDummySize > 0)//go to extra space
+	{		
+		for(S32 i = 0 ; i < mDummySize; i++)
+		{
+			if(*((U32*)mBuffer + i) != 0xffffffff)
+			{
+				bits = (U32*)mBuffer + i ;
+				k = i + 1 ;
+				break ;
+			}
+		}
+	}	
+	S32 idx = 0 ;
+	U32 tmp = *bits ;
+	for(; tmp & 1 ; tmp >>= 1, idx++) ;
+
+	//set the slot reserved
+	if(!idx)
+	{
+		*bits |= 1 ;
+	}
+	else
+	{
+		*bits |= (1 << idx) ;
+	}
+
+	mAllocatedSlots++ ;
+
+	return mBuffer + mDummySize * sizeof(U32) + (k * 32 + idx) * mSlotSize ;
+}
+
+void  LLPrivateMemoryPool::LLMemoryBlock::free(void* addr) 
+{
+	U32 idx = ((char*) addr - mBuffer - mDummySize * sizeof(U32)) / mSlotSize ;
+
+	U32* bits = &mUsageBits ;
+	if(idx > 32)
+	{
+		bits = (U32*)mBuffer + (idx - 32) / 32 ;
+	}
+	if(idx & 31)
+	{
+		*bits &= ~(1 << (idx & 31)) ;
+	}
+	else
+	{
+		*bits &= ~1 ;
+	}
+
+	mAllocatedSlots-- ;
+}
+
+//-------------------------------------------------------------------
+//class LLMemoryChunk
+//--------------------------------------------------------------------
+LLPrivateMemoryPool::LLMemoryChunk::LLMemoryChunk()
+{
+	//empty
+}
+
+LLPrivateMemoryPool::LLMemoryChunk::~LLMemoryChunk()
+{
+	//empty
+}
+
+void LLPrivateMemoryPool::LLMemoryChunk::init(char* buffer, U32 buffer_size, U32 min_slot_size, U32 max_slot_size, U32 min_block_size, U32 max_block_size) 
+{
+	mBuffer = buffer ;
+	mBufferSize = buffer_size ;
+
+	mMetaBuffer = mBuffer + sizeof(LLMemoryChunk) ;
+
+	mMinBlockSize = min_block_size;
+	mMaxBlockSize = max_block_size;
+	mMinSlotSize = min_slot_size;
+	mBlockLevels = max_block_size / min_block_size ;
+	mPartitionLevels = mMaxBlockSize / mMinBlockSize + 1 ;
+
+	S32 max_num_blocks = (buffer_size - sizeof(LLMemoryChunk) - mBlockLevels * sizeof(LLMemoryBlock*) - mPartitionLevels * sizeof(LLMemoryBlock*)) / 
+		                 (mMinBlockSize + sizeof(LLMemoryBlock)) ;
+	//meta data space
+	mBlocks = (LLMemoryBlock*)mMetaBuffer ;
+	mAvailBlockList = (LLMemoryBlock**)((char*)mBlocks + sizeof(LLMemoryBlock) * max_num_blocks) ; 
+	mFreeSpaceList = (LLMemoryBlock**)((char*)mAvailBlockList + sizeof(LLMemoryBlock*) * mBlockLevels) ; 
+	
+	//data buffer
+	mDataBuffer = (char*)mFreeSpaceList + sizeof(LLMemoryBlock*) * mPartitionLevels ;
+
+	//init
+	for(U32 i = 0 ; i < mBlockLevels; i++)
+	{
+		mAvailBlockList[i] = NULL ;
+	}
+	for(U32 i = 0 ; i < mPartitionLevels ; i++)
+	{
+		mFreeSpaceList[i] = NULL ;
+	}
+
+	mBlocks[0].setBuffer(mDataBuffer, buffer_size - (mDataBuffer - mBuffer)) ;
+	addToFreeSpace(&mBlocks[0]) ;
+
+	mKey = (U32)mBuffer ;
+	mNext = NULL ;
+	mPrev = NULL ;
+}
+
+//static 
+U32 LLPrivateMemoryPool::LLMemoryChunk::getMaxOverhead(U32 data_buffer_size, U32 min_page_size) 
+{
+	return 2048 +
+		sizeof(LLMemoryBlock) * (data_buffer_size / min_page_size) ;
+}
+
+char* LLPrivateMemoryPool::LLMemoryChunk::allocate(U32 size)
+{
+	char* p = NULL ;
+	U32 blk_idx = size / mMinSlotSize ;
+	if(mMinSlotSize * blk_idx < size)
+	{
+		blk_idx++ ;
+	}
+
+	//check if there is free block available
+	if(mAvailBlockList[blk_idx])
+	{
+		LLMemoryBlock* blk = mAvailBlockList[blk_idx] ;
+		p = blk->allocate() ;
+
+		if(blk->isFull())
+		{
+			//removeFromFreelist
+			popAvailBlockList(blk_idx) ;
+		}
+	}
+
+	//ask for a new block
+	if(!p)
+	{
+		LLMemoryBlock* blk = addBlock(blk_idx) ;
+		if(blk)
+		{
+			p = blk->allocate() ;
+
+			if(blk->isFull())
+			{
+				//removeFromFreelist
+				popAvailBlockList(blk_idx) ;
+			}
+		}
+	}
+
+	//ask for space from higher level blocks
+	if(!p)
+	{
+		for(S32 i = blk_idx + 1 ; i < mBlockLevels; i++)
+		{
+			if(mAvailBlockList[i])
+			{
+				LLMemoryBlock* blk = mAvailBlockList[i] ;
+				p = blk->allocate() ;
+
+				if(blk->isFull())
+				{
+					//removeFromFreelist
+					popAvailBlockList(i) ;
+				}
+				break ;
+			}
+		}
+	}
+
+	return p ;
+}
+
+void LLPrivateMemoryPool::LLMemoryChunk::free(void* addr)
+{	
+	LLMemoryBlock* blk = (LLMemoryBlock*)(mMetaBuffer + (((char*)addr - mDataBuffer) / mMinBlockSize) * sizeof(LLMemoryBlock)) ;
+	blk = blk->mSelf ;
+
+	bool was_full = blk->isFull() ;
+	blk->free(addr) ;
+
+	if(blk->empty())
+	{
+		removeBlock(blk) ;
+	}
+	else if(was_full)
+	{
+		addToAvailBlockList(blk) ;
+	}
+}
+
+LLPrivateMemoryPool::LLMemoryBlock* LLPrivateMemoryPool::LLMemoryChunk::addBlock(U32 blk_idx)
+{	
+	U32 slot_size = mMinSlotSize * (blk_idx + 1) ;
+	U32 preferred_block_size = llmax(mMinBlockSize, slot_size * 32) ;
+	preferred_block_size = llmin(preferred_block_size, mMaxBlockSize) ;	
+
+	U32 idx = preferred_block_size / mMinBlockSize ;	
+	preferred_block_size = idx * mMinBlockSize ; //round to integer times of mMinBlockSize.
+
+	LLMemoryBlock* blk = NULL ;
+	
+	if(mFreeSpaceList[idx])//if there is free slot for blk_idx
+	{
+		blk = createNewBlock(&mFreeSpaceList[idx], preferred_block_size, slot_size, blk_idx) ;
+	}
+	else if(mFreeSpaceList[mPartitionLevels - 1]) //search free pool
+	{		
+		blk = createNewBlock(&mFreeSpaceList[mPartitionLevels - 1], preferred_block_size, slot_size, blk_idx) ;
+	}
+	else //search for other non-preferred but enough space slot.
+	{
+		for(U32 i = idx - 1 ; i >= 0 ; i--) //search the small slots first
+		{
+			if(mFreeSpaceList[i])
+			{
+				//create a NEW BLOCK THERE.
+				if(mFreeSpaceList[i]->getBufferSize() >= slot_size) //at least there is space for one slot.
+				{
+					blk = createNewBlock(&mFreeSpaceList[i], preferred_block_size, slot_size, blk_idx) ;
+				}
+				break ;
+			} 
+		}
+
+		if(!blk)
+		{
+			for(U16 i = idx + 1 ; i < mPartitionLevels - 1; i++) //search the large slots 
+			{
+				if(mFreeSpaceList[i])
+				{
+					//create a NEW BLOCK THERE.
+					blk = createNewBlock(&mFreeSpaceList[i], preferred_block_size, slot_size, blk_idx) ;
+					break ;
+				} 
+			}
+		}
+	}
+
+	return blk ;
+}
+
+LLPrivateMemoryPool::LLMemoryBlock* LLPrivateMemoryPool::LLMemoryChunk::createNewBlock(LLMemoryBlock** cur_idxp, U32 buffer_size, U32 slot_size, U32 blk_idx)
+{
+	LLMemoryBlock* blk = *cur_idxp ;
+	
+	buffer_size = llmin(buffer_size, blk->getBufferSize()) ;
+	U32 new_free_blk_size = blk->getBufferSize() - buffer_size ;
+	if(new_free_blk_size < mMinBlockSize) //can not partition the memory into size smaller than mMinBlockSize
+	{
+		buffer_size += new_free_blk_size ;
+		new_free_blk_size = 0 ;
+	}
+	blk->init(blk->getBuffer(), buffer_size, slot_size) ;
+		
+	if(new_free_blk_size > 0) //cur_idx still has free space
+	{
+		LLMemoryBlock* next_blk = blk + (buffer_size / mMinBlockSize) ;
+		next_blk->setBuffer(blk->getBuffer() + buffer_size, new_free_blk_size) ;
+		
+		if(new_free_blk_size > mMaxBlockSize) //stays in the free pool
+		{
+			next_blk->mPrev = NULL ;
+			next_blk->mNext = blk->mNext ;
+			if(next_blk->mNext)
+			{
+				next_blk->mNext->mPrev = next_blk ;
+			}
+			*cur_idxp = next_blk ;
+		}
+		else
+		{
+			*cur_idxp = blk->mNext ; //move to the next slot
+			(*cur_idxp)->mPrev = NULL ;
+
+			addToFreeSpace(next_blk) ;
+		}		
+	}
+	else //move to the next block
+	{
+		*cur_idxp = blk->mNext ;
+		(*cur_idxp)->mPrev = NULL ;
+	}
+
+	//insert to the available block list...
+	blk->mNext = NULL ;
+	blk->mPrev = NULL ;
+	blk->mSelf = blk ;
+	mAvailBlockList[blk_idx] = blk ;
+
+	//mark the address map
+	U32 end = (buffer_size / mMinBlockSize) ;
+	for(U32 i = 1 ; i < end ; i++)
+	{
+		(blk + i)->mSelf = blk ;
+	}
+
+	return blk ;
+}
+
+void LLPrivateMemoryPool::LLMemoryChunk::removeBlock(LLMemoryBlock* blk)
+{
+	//remove from the available block list
+	if(blk->mPrev)
+	{
+		blk->mPrev->mNext = blk->mNext ;
+	}
+	if(blk->mNext)
+	{
+		blk->mNext->mPrev = blk->mPrev ;
+	}
+	
+	//mark it free
+	blk->setBuffer(blk->getBuffer(), blk->getBufferSize()) ;
+
+	//merge blk with neighbors if possible
+	if(blk->getBuffer() > mDataBuffer) //has the left neighbor
+	{
+		if((blk - 1)->mSelf->isFree())
+		{
+			removeFromFreeSpace((blk - 1)->mSelf);
+			(blk - 1)->mSelf->setBuffer((blk-1)->mSelf->getBuffer(), (blk-1)->mSelf->getBufferSize() + blk->getBufferSize()) ;
+			blk = (blk - 1)->mSelf ;
+		}
+	}
+	if(blk->getBuffer() + blk->getBufferSize() < mBuffer + mBufferSize) //has the right neighbor
+	{
+		U32 d = blk->getBufferSize() / mMinBlockSize ;
+		if((blk + d)->isFree())
+		{
+			removeFromFreeSpace(blk + d) ;
+			blk->setBuffer(blk->getBuffer(), blk->getBufferSize() + (blk + d)->getBufferSize()) ;
+		}
+	}
+
+	addToFreeSpace(blk) ;
+
+	return ;
+}
+
+//the top block in the list is full, pop it out of the list
+void LLPrivateMemoryPool::LLMemoryChunk::popAvailBlockList(U32 blk_idx) 
+{
+	if(mAvailBlockList[blk_idx])
+	{
+		LLMemoryBlock* next = mAvailBlockList[blk_idx]->mNext ;
+		next->mPrev = NULL ;
+		mAvailBlockList[blk_idx]->mNext = NULL ;
+		mAvailBlockList[blk_idx] = next ;
+	}
+}
+
+void LLPrivateMemoryPool::LLMemoryChunk::addToFreeSpace(LLMemoryBlock* blk) 
+{
+	U16 free_idx = blk->getBufferSize() / mMinBlockSize ;
+	(blk + free_idx)->mSelf = blk ; //mark the end pointing back to the head.
+	free_idx = llmin(free_idx, (U16)(mPartitionLevels - 1)) ;
+
+	blk->mNext = mFreeSpaceList[free_idx] ;
+	if(mFreeSpaceList[free_idx])
+	{
+		mFreeSpaceList[free_idx]->mPrev = blk ;
+	}
+	mFreeSpaceList[free_idx] = blk ;
+	blk->mPrev = NULL ;
+	blk->mSelf = blk ;
+	
+	return ;
+}
+
+void LLPrivateMemoryPool::LLMemoryChunk::removeFromFreeSpace(LLMemoryBlock* blk) 
+{
+	U16 free_idx = blk->getBufferSize() / mMinBlockSize ;
+	free_idx = llmin(free_idx, (U16)(mPartitionLevels - 1)) ;
+
+	if(mFreeSpaceList[free_idx] == blk)
+	{
+		mFreeSpaceList[free_idx] = blk->mNext ;
+	}
+	if(blk->mPrev)
+	{
+		blk->mPrev->mNext = blk->mNext ;
+	}
+	if(blk->mNext)
+	{
+		blk->mNext->mPrev = blk->mPrev ;
+	}
+	
+	return ;
+}
+
+void LLPrivateMemoryPool::LLMemoryChunk::addToAvailBlockList(LLMemoryBlock* blk) 
+{
+	U32 blk_idx = blk->getSlotSize() / mMinSlotSize ;
+
+	blk->mNext = mAvailBlockList[blk_idx] ;
+	if(blk->mNext)
+	{
+		blk->mNext->mPrev = blk ;
+	}
+	blk->mPrev = NULL ;
+	
+	return ;
+}
+
+//-------------------------------------------------------------------
+//class LLPrivateMemoryPool
+//--------------------------------------------------------------------
+LLPrivateMemoryPool::LLPrivateMemoryPool(U32 max_size, bool threaded) :
+	mMutexp(NULL),
+	mMaxPoolSize(max_size),
+	mReservedPoolSize(0)
+{
+	if(threaded)
+	{
+		mMutexp = new LLMutex(NULL) ;
+	}
+
+	for(S32 i = 0 ; i < SUPER_ALLOCATION ; i++)
+	{
+		mChunkList[i] = NULL ;
+	}
+
+	mChunkVectorCapacity = 128 ;
+	mChunks.resize(mChunkVectorCapacity) ; //at most 128 chunks
+	mNumOfChunks = 0 ;
+}
+
+LLPrivateMemoryPool::~LLPrivateMemoryPool()
+{
+	destroyPool();
+	delete mMutexp ;
+}
+
+char* LLPrivateMemoryPool::allocate(U32 size)
+{	
+	const static U32 MAX_BLOCK_SIZE = 4 * 1024 * 1024 ; //4MB
+
+	//if the asked size larger than MAX_BLOCK_SIZE, fetch from heap directly, the pool does not manage it
+	if(size >= MAX_BLOCK_SIZE)
+	{
+		return new char[size] ;
+	}
+
+	char* p = NULL ;
+
+	//find the appropriate chunk
+	S32 chunk_idx = getChunkIndex(size) ;
+	
+	lock() ;
+
+	LLMemoryChunk* chunk = mChunkList[chunk_idx];
+	while(chunk)
+	{
+		if(p = chunk->allocate(size))
+		{
+			break ;
+		}
+		chunk = chunk->mNext ;
+	}
+	
+	//fetch new memory chunk
+	if(!p)
+	{
+		chunk = addChunk(chunk_idx) ;
+		p = chunk->allocate(size) ;
+	}
+
+	unlock() ;
+
+	return p ;
+}
+
+void LLPrivateMemoryPool::free(void* addr)
+{
+	lock() ;
+	
+	LLMemoryChunk* chunk = mChunks[findChunk((char*)addr)] ;
+	if(!chunk)
+	{
+		delete[] (char*)addr ; //release from heap
+	}
+	else
+	{
+		chunk->free(addr) ;
+
+		if(chunk->empty())
+		{
+			removeChunk(chunk) ;
+		}
+	}
+	
+	unlock() ;
+}
+
+void LLPrivateMemoryPool::dump()
+{
+}
+
+void LLPrivateMemoryPool::lock()
+{
+	if(mMutexp)
+	{
+		mMutexp->lock() ;
+	}
+}
+
+void LLPrivateMemoryPool::unlock()
+{
+	if(mMutexp)
+	{
+		mMutexp->unlock() ;
+	}
+}
+
+S32  LLPrivateMemoryPool::getChunkIndex(U32 size) 
+{
+	if(size < 2048)
+	{
+		return 0 ;
+	}
+	else if(size  < (512 << 10))
+	{
+		return 1 ;
+	}
+	else 
+	{
+		return 2 ;
+	}
+}
+
+//destroy the entire pool
+void  LLPrivateMemoryPool::destroyPool()
+{
+	for(U16 i = 0 ; i < mNumOfChunks ; i++)
+	{
+		delete[] mChunks[i]->getBuffer() ;
+	}
+	mNumOfChunks = 0 ;
+	for(S32 i = 0 ; i < SUPER_ALLOCATION ; i++)
+	{
+		mChunkList[i] = NULL ;
+	}
+}
+
+LLPrivateMemoryPool::LLMemoryChunk* LLPrivateMemoryPool::addChunk(S32 chunk_index)
+{
+	static const U32 MIN_BLOCK_SIZES[SUPER_ALLOCATION] = {2 << 10, 32 << 10, 64 << 10} ;
+	static const U32 MAX_BLOCK_SIZES[SUPER_ALLOCATION] = {64 << 10, 1 << 20, 4 << 20} ;
+	static const U32 MIN_SLOT_SIZES[SUPER_ALLOCATION]  = {8, 2 << 10, 512 << 10};
+	static const U32 MAX_SLOT_SIZES[SUPER_ALLOCATION]  = {(2 << 10) - 8, (512 - 2) << 10, 4 << 20};
+
+	U32 preferred_size ;
+	U32 overhead ;
+	if(chunk_index < LARGE_ALLOCATION)
+	{
+		preferred_size = (4 << 20) ; //4MB
+		overhead = LLMemoryChunk::getMaxOverhead(preferred_size, MIN_BLOCK_SIZES[chunk_index]) ;
+	}
+	else
+	{
+		preferred_size = (16 << 20) ; //16MB
+		overhead = LLMemoryChunk::getMaxOverhead(preferred_size, MIN_BLOCK_SIZES[chunk_index]) ;
+	}
+	char* buffer = new(std::nothrow) char[preferred_size + overhead] ;
+	if(!buffer)
+	{
+		return NULL ;
+	}
+
+	LLMemoryChunk* chunk = new (buffer) LLMemoryChunk() ;
+	chunk->init(buffer, preferred_size + overhead, MIN_SLOT_SIZES[chunk_index],
+		MAX_SLOT_SIZES[chunk_index], MIN_BLOCK_SIZES[chunk_index], MAX_BLOCK_SIZES[chunk_index]) ;
+
+	//add to the head of the linked list
+	chunk->mNext = mChunkList[chunk_index] ;
+	if(mChunkList[chunk_index])
+	{
+		mChunkList[chunk_index]->mPrev = chunk ;
+	}
+	chunk->mPrev = NULL ;
+	mChunkList[chunk_index] = chunk ;
+
+	//insert into the array
+	llassert_always(mNumOfChunks + 1 < mChunkVectorCapacity) ;
+	if(!mNumOfChunks)
+	{
+		mChunks[0] = chunk ;
+	}
+	else
+	{
+		U16 k ;
+		if(mChunks[0]->getBuffer() > chunk->getBuffer())
+		{
+			k = 0 ;
+		}
+		else
+		{
+			k = findChunk(chunk->getBuffer()) + 1 ;
+		}
+		for(U16 i = mNumOfChunks ; i > k ; i++)
+		{
+			mChunks[i] = mChunks[i-1] ;
+		}
+		mChunks[k] = chunk ;
+	}
+	mNumOfChunks++;
+
+	return chunk ;
+}
+
+void LLPrivateMemoryPool::removeChunk(LLMemoryChunk* chunk) 
+{
+	//remove from the linked list
+	if(chunk->mPrev)
+	{
+		chunk->mPrev->mNext = chunk->mNext ;
+	}
+	if(chunk->mNext)
+	{
+		chunk->mNext->mPrev = chunk->mPrev ;
+	}
+
+	//remove from the array
+	U16 k = findChunk(chunk->getBuffer()) ;
+	mNumOfChunks--;
+	for(U16 i = k ; i < mNumOfChunks ; i++)
+	{
+		mChunks[i] = mChunks[i+1] ;
+	}
+
+	//release memory
+	delete[] chunk->getBuffer() ;
+}
+
+U16 LLPrivateMemoryPool::findChunk(const char* addr) 
+{
+	llassert_always(mNumOfChunks > 0) ;
+	
+	U16 s = 0, e = mNumOfChunks;
+	U16 k = (s + e) / 2 ;
+	while(s < e)
+	{
+		if(mChunks[k]->mKey > (U32)addr)
+		{
+			e = k ;
+		}
+		else if(k < mNumOfChunks - 1 && mChunks[k+1]->mKey < (U32)addr)
+		{
+			s = k ;
+		}
+		else
+		{
+			break ;
+		}
+
+		k = (s + e) / 2 ;
+	}
+
+	return k ;
+}
+
+//--------------------------------------------------------------------
+//class LLPrivateMemoryPoolTester
+LLPrivateMemoryPoolTester* LLPrivateMemoryPoolTester::sInstance = NULL ;
+LLPrivateMemoryPool* LLPrivateMemoryPoolTester::sPool = NULL ;
+LLPrivateMemoryPoolTester::LLPrivateMemoryPoolTester()
+{	
+}
+	
+LLPrivateMemoryPoolTester::~LLPrivateMemoryPoolTester() 
+{	
+}
+
+//static 
+LLPrivateMemoryPoolTester* LLPrivateMemoryPoolTester::getInstance() 
+{
+	if(!sInstance)
+	{
+		sInstance = new LLPrivateMemoryPoolTester() ;
+	}
+	return sInstance ;
+}
+
+//static 
+void LLPrivateMemoryPoolTester::destroy()
+{
+	if(sInstance)
+	{
+		delete sInstance ;
+		sInstance = NULL ;
+	}
+
+	if(sPool)
+	{
+		delete sPool ;
+		sPool = NULL ;
+	}
+}
+
+void LLPrivateMemoryPoolTester::run() 
+{
+	const U32 max_pool_size = 16 << 20 ;
+	const bool threaded = false ;
+	if(!sPool)
+	{
+		sPool = new LLPrivateMemoryPool(max_pool_size, threaded) ;
+	}
+
+	//run the test
+	correctnessTest() ;
+	reliabilityTest() ;
+	performanceTest() ;
+	fragmentationtest() ;
+}
+
+void LLPrivateMemoryPoolTester::correctnessTest() 
+{
+	//try many different sized allocation, fill the memory fully to see if allocation is right.
+
+}
+
+void LLPrivateMemoryPoolTester::reliabilityTest() 
+void LLPrivateMemoryPoolTester::performanceTest() 
+void LLPrivateMemoryPoolTester::fragmentationtest() 
+
+void* LLPrivateMemoryPoolTester::operator new(size_t size)

+{

+	return (void*)sPool->allocate(size) ;

+}

+

+void  LLPrivateMemoryPoolTester::operator delete(void* addr)

+{

+	sPool->free(addr) ;

+}

+

+//--------------------------------------------------------------------

diff --git a/indra/llcommon/llmemory.h b/indra/llcommon/llmemory.h
index 9bf4248bb7..d9e93d0e96 100644
--- a/indra/llcommon/llmemory.h
+++ b/indra/llcommon/llmemory.h
@@ -26,8 +26,6 @@
 #ifndef LLMEMORY_H
 #define LLMEMORY_H
 
-
-
 extern S32 gTotalDAlloc;
 extern S32 gTotalDAUse;
 extern S32 gDACount;
@@ -44,8 +42,180 @@ public:
 	// Return the resident set size of the current process, in bytes.
 	// Return value is zero if not known.
 	static U64 getCurrentRSS();
+
+	static void* tryToAlloc(void* address, U32 size);
+	static void initMaxHeapSizeGB(F32 max_heap_size_gb, BOOL prevent_heap_failure);
+	static void updateMemoryInfo() ;
+	static void logMemoryInfo(BOOL update = FALSE);
+	static S32  isMemoryPoolLow();
+
+	static U32 getAvailableMemKB() ;
+	static U32 getMaxMemKB() ;
+	static U32 getAllocatedMemKB() ;
 private:
 	static char* reserveMem;
+	static U32 sAvailPhysicalMemInKB ;
+	static U32 sMaxPhysicalMemInKB ;
+	static U32 sAllocatedMemInKB;
+	static U32 sAllocatedPageSizeInKB ;
+
+	static U32 sMaxHeapSizeInKB;
+	static BOOL sEnableMemoryFailurePrevention;
+};
+
+class LL_COMMON_API LLPrivateMemoryPool
+{
+public:
+	class LL_COMMON_API LLMemoryBlock //each block is devided into slots uniformly
+	{
+	public: 
+		LLMemoryBlock() ;
+		~LLMemoryBlock() ;
+
+		void init(char* buffer, U32 buffer_size, U32 slot_size) ;
+		void setBuffer(char* buffer, U32 buffer_size) ;
+
+		char* allocate() ;
+		void  free(void* addr) ;
+
+		bool empty() {return !mAllocatedSlots;}
+		bool isFull() {return mAllocatedSlots == mTotalSlots;}
+		bool isFree() {return !mTotalSlots;}
+
+		U32  getSlotSize()const {return mSlotSize;}
+		U32  getTotalSlots()const {return mTotalSlots;}
+		U32  getBufferSize()const {return mBufferSize;}
+		char* getBuffer() const {return mBuffer;}
+
+	private:
+		char* mBuffer;
+		U32   mSlotSize ; //when the block is not initialized, it is the buffer size.
+		U32   mBufferSize ;
+		U32   mUsageBits ;
+		U8    mTotalSlots ;
+		U8    mAllocatedSlots ;
+		U8    mDummySize ; //size of extra U32 reserved for mUsageBits.
+
+	public:
+		LLMemoryBlock* mPrev ;
+		LLMemoryBlock* mNext ;
+		LLMemoryBlock* mSelf ;
+	};
+
+	class LL_COMMON_API LLMemoryChunk //is divided into memory blocks.
+	{
+	public:
+		LLMemoryChunk() ;
+		~LLMemoryChunk() ;
+
+		void init(char* buffer, U32 buffer_size, U32 min_slot_size, U32 max_slot_size, U32 min_block_size, U32 max_block_size) ;
+		void setBuffer(char* buffer, U32 buffer_size) ;
+
+		bool empty() ;
+		
+		char* allocate(U32 size) ;
+		void  free(void* addr) ;
+
+		const char* getBuffer() const {return mBuffer;}
+		U32 getBufferSize() const {return mBufferSize;}
+
+		static U32 getMaxOverhead(U32 data_buffer_size, U32 min_page_size) ;
+	
+	private:
+		LLMemoryBlock* addBlock(U32 blk_idx) ;
+		void popAvailBlockList(U32 blk_idx) ;
+		void addToFreeSpace(LLMemoryBlock* blk) ;
+		void removeFromFreeSpace(LLMemoryBlock* blk) ;
+		void removeBlock(LLMemoryBlock* blk) ;
+		void addToAvailBlockList(LLMemoryBlock* blk) ;
+		LLMemoryBlock* createNewBlock(LLMemoryBlock** cur_idxp, U32 buffer_size, U32 slot_size, U32 blk_idx) ;
+
+	private:
+		LLMemoryBlock** mAvailBlockList ;//256 by mMinSlotSize
+		LLMemoryBlock** mFreeSpaceList;
+		LLMemoryBlock*  mBlocks ; //index of blocks by address.
+		
+		char* mBuffer ;
+		U32   mBufferSize ;
+		char* mDataBuffer ;
+		char* mMetaBuffer ;
+		U32   mMinBlockSize ;
+		U32   mMaxBlockSize;
+		U32   mMinSlotSize ;
+		U16   mBlockLevels;
+		U16   mPartitionLevels;
+
+	public:
+		//form a linked list
+		LLMemoryChunk* mNext ;
+		LLMemoryChunk* mPrev ;
+
+		U32 mKey ; //= mBuffer
+	} ;
+
+public:
+	LLPrivateMemoryPool(U32 max_size, bool threaded) ;
+	~LLPrivateMemoryPool() ;
+
+	char *allocate(U32 size) ;
+	void  free(void* addr) ;
+	void  dump() ;
+
+private:
+	void lock() ;
+	void unlock() ;	
+	S32 getChunkIndex(U32 size) ;
+	LLMemoryChunk*  addChunk(S32 chunk_index) ;
+	void removeChunk(LLMemoryChunk* chunk) ;
+	U16  findChunk(const char* addr) ;
+	void destroyPool() ;
+
+private:
+	LLMutex* mMutexp ;
+	U32  mMaxPoolSize;
+	U32  mReservedPoolSize ;
+	
+	enum
+	{
+		SMALL_ALLOCATION = 0, //from 8 bytes to 2KB(exclusive), page size 2KB, max chunk size is 4MB.
+		MEDIUM_ALLOCATION,    //from 2KB to 512KB(exclusive), page size 32KB, max chunk size 4MB
+		LARGE_ALLOCATION,     //from 512KB to 4MB(inclusive), page size 64KB, max chunk size 16MB
+		SUPER_ALLOCATION      //allocation larger than 4MB.
+	};
+
+	LLMemoryChunk* mChunkList[SUPER_ALLOCATION] ; //all memory chunks reserved by this pool, sorted by address
+	std::vector<LLMemoryChunk*> mChunks ;
+	U16 mNumOfChunks ;
+	U16 mChunkVectorCapacity ;
+};
+
+//
+//the below singleton is used to test the private memory pool.
+//
+class LLPrivateMemoryPoolTester
+{
+private:
+	LLPrivateMemoryPoolTester() ;
+	~LLPrivateMemoryPoolTester() ;
+
+public:
+	static LLPrivateMemoryPoolTester* getInstance() ;
+	static void destroy() ;
+
+	void run() ;	
+
+private:
+	void correctnessTest() ;
+	void reliabilityTest() ;
+	void performanceTest() ;
+	void fragmentationtest() ;
+
+	void* operator new(size_t);

+    void  operator delete(void*);
+
+private:
+	static LLPrivateMemoryPoolTester* sInstance;
+	static LLPrivateMemoryPool* sPool ;
 };
 
 // LLRefCount moved to llrefcount.h
diff --git a/indra/llcommon/llsys.cpp b/indra/llcommon/llsys.cpp
index 10cdc7087b..7968e53c13 100644
--- a/indra/llcommon/llsys.cpp
+++ b/indra/llcommon/llsys.cpp
@@ -636,22 +636,20 @@ U32 LLMemoryInfo::getPhysicalMemoryClamped() const
 }
 
 //static
-void LLMemoryInfo::getAvailableMemoryKB(U32& avail_physical_mem_kb, U32& avail_virtual_mem_kb)
+U32 LLMemoryInfo::getAvailableMemoryKB()
 {
 #if LL_WINDOWS
 	MEMORYSTATUSEX state;
 	state.dwLength = sizeof(state);
 	GlobalMemoryStatusEx(&state);
 
-	avail_physical_mem_kb = (U32)(state.ullAvailPhys/1024) ;
-	avail_virtual_mem_kb = (U32)(state.ullAvailVirtual/1024) ;
+	return (U32)(state.ullAvailPhys/1024) ;
 
 #else
 	//do not know how to collect available memory info for other systems.
 	//leave it blank here for now.
 
-	avail_physical_mem_kb = -1 ;
-	avail_virtual_mem_kb = -1 ;
+	return -1;
 #endif
 }
 
diff --git a/indra/llcommon/llsys.h b/indra/llcommon/llsys.h
index 41a4f25000..580eee4e8d 100644
--- a/indra/llcommon/llsys.h
+++ b/indra/llcommon/llsys.h
@@ -116,7 +116,7 @@ public:
 	U32 getPhysicalMemoryClamped() const; ///< Memory size in clamped bytes
 
 	//get the available memory infomation in KiloBytes.
-	static void getAvailableMemoryKB(U32& avail_physical_mem_kb, U32& avail_virtual_mem_kb);
+	static U32 getAvailableMemoryKB();
 };
 
 
diff --git a/indra/llrender/llvertexbuffer.cpp b/indra/llrender/llvertexbuffer.cpp
index 02160b09c4..19269c2a31 100644
--- a/indra/llrender/llvertexbuffer.cpp
+++ b/indra/llrender/llvertexbuffer.cpp
@@ -33,6 +33,7 @@
 #include "llglheaders.h"
 #include "llmemtype.h"
 #include "llrender.h"
+#include "llmemory.h"
 
 //============================================================================
 
@@ -857,11 +858,8 @@ U8* LLVertexBuffer::mapBuffer(S32 access)
 			log_glerror();
 
 			//check the availability of memory
-			U32 avail_phy_mem, avail_vir_mem;
-			LLMemoryInfo::getAvailableMemoryKB(avail_phy_mem, avail_vir_mem) ;
-			llinfos << "Available physical mwmory(KB): " << avail_phy_mem << llendl ; 
-			llinfos << "Available virtual memory(KB): " << avail_vir_mem << llendl;
-
+			LLMemory::logMemoryInfo(TRUE) ; 
+			
 			//--------------------
 			//print out more debug info before crash
 			llinfos << "vertex buffer size: (num verts : num indices) = " << getNumVerts() << " : " << getNumIndices() << llendl ;
@@ -884,6 +882,7 @@ U8* LLVertexBuffer::mapBuffer(S32 access)
 		if (!mMappedIndexData)
 		{
 			log_glerror();
+			LLMemory::logMemoryInfo(TRUE) ;
 
 			GLint buff;
 			glGetIntegerv(GL_ELEMENT_ARRAY_BUFFER_BINDING_ARB, &buff);
diff --git a/indra/llxml/llcontrol.h b/indra/llxml/llcontrol.h
index 93975579cc..70749b8ee9 100644
--- a/indra/llxml/llcontrol.h
+++ b/indra/llxml/llcontrol.h
@@ -385,7 +385,8 @@ class LLCachedControl
 {
 public:
 	LLCachedControl(LLControlGroup& group,
-					const std::string& name, 
+					const std::string& name,
+
 					const T& default_value, 
 					const std::string& comment = "Declared In Code")
 	{
diff --git a/indra/newview/app_settings/settings.xml b/indra/newview/app_settings/settings.xml
index 535bc95287..905c683f69 100644
--- a/indra/newview/app_settings/settings.xml
+++ b/indra/newview/app_settings/settings.xml
@@ -5153,6 +5153,17 @@
       <key>Value</key>
       <real>48.0</real>
     </map>
+    <key>MaxHeapSize</key>
+    <map>
+      <key>Comment</key>
+      <string>Maximum heap size (GB)</string>
+      <key>Persist</key>
+      <integer>1</integer>
+      <key>Type</key>
+      <string>F32</string>
+      <key>Value</key>
+      <real>1.6</real>
+    </map>
     <key>MaxSelectDistance</key>
     <map>
       <key>Comment</key>
@@ -5329,6 +5340,17 @@
     <key>Value</key>
     <integer>1</integer>
   </map>
+  <key>MemeoyFailurePreventionEnabled</key>
+  <map>
+    <key>Comment</key>
+    <string>If set, the viewer will quit to avoid crash when memory failure happens</string>
+    <key>Persist</key>
+    <integer>0</integer>
+    <key>Type</key>
+    <string>Boolean</string>
+    <key>Value</key>
+    <integer>1</integer>
+  </map>
   <key>MemoryLogFrequency</key>
         <map>
         <key>Comment</key>
diff --git a/indra/newview/llappviewer.cpp b/indra/newview/llappviewer.cpp
index 3a98749c0f..84e36ac3c7 100644
--- a/indra/newview/llappviewer.cpp
+++ b/indra/newview/llappviewer.cpp
@@ -604,7 +604,7 @@ LLAppViewer::~LLAppViewer()
 }
 
 bool LLAppViewer::init()
-{
+{	
 	//
 	// Start of the application
 	//
@@ -632,6 +632,9 @@ bool LLAppViewer::init()
 	if (!initConfiguration())
 		return false;
 
+	//set the max heap size.
+	initMaxHeapSize() ;
+
 	// write Google Breakpad minidump files to our log directory
 	std::string logdir = gDirUtilp->getExpandedFilename(LL_PATH_LOGS, "");
 	logdir += gDirUtilp->getDirDelimiter();
@@ -949,6 +952,96 @@ bool LLAppViewer::init()
 	return true;
 }
 
+void LLAppViewer::initMaxHeapSize()
+{
+	//set the max heap size.
+	//here is some info regarding to the max heap size:
+	//------------------------------------------------------------------------------------------
+	// OS       | setting | SL address bits | max manageable memory space | max heap size
+	// Win 32   | default | 32-bit          | 2GB                         | < 1.7GB
+	// Win 32   | /3G     | 32-bit          | 3GB                         | < 1.7GB or 2.7GB
+	//Linux 32  | default | 32-bit          | 3GB                         | < 2.7GB
+	//Linux 32  |HUGEMEM  | 32-bit          | 4GB                         | < 3.7GB
+	//64-bit OS |default  | 32-bit          | 4GB                         | < 3.7GB
+	//64-bit OS |default  | 64-bit          | N/A (> 4GB)                 | N/A (> 4GB)
+	//------------------------------------------------------------------------------------------
+	//currently SL is built under 32-bit setting, we set its max heap size no more than 1.6 GB.
+
+	//F32 max_heap_size_gb = llmin(1.6f, (F32)gSavedSettings.getF32("MaxHeapSize")) ;
+	F32 max_heap_size_gb = gSavedSettings.getF32("MaxHeapSize") ;
+	BOOL enable_mem_failure_prevention = (BOOL)gSavedSettings.getBOOL("MemeoyFailurePreventionEnabled") ;
+
+	LLMemory::initMaxHeapSizeGB(max_heap_size_gb, enable_mem_failure_prevention) ;
+}
+
+void LLAppViewer::checkMemory()
+{
+	const static F32 MEMORY_CHECK_INTERVAL = 1.0f ; //second
+	const static F32 MAX_QUIT_WAIT_TIME = 30.0f ; //seconds
+	const static U32 MAX_SIZE_CHECKED_MEMORY_BLOCK = 64 * 1024 * 1024 ; //64 MB
+	//static F32 force_quit_timer = MAX_QUIT_WAIT_TIME + MEMORY_CHECK_INTERVAL ;
+	static void* last_reserved_address = NULL ;
+
+	if(MEMORY_CHECK_INTERVAL > mMemCheckTimer.getElapsedTimeF32())
+	{
+		return ;
+	}
+	mMemCheckTimer.reset() ;
+
+	if(gGLManager.mDebugGPU)
+	{
+		//update the availability of memory
+		LLMemory::updateMemoryInfo() ;
+	}
+
+	//check the virtual address space fragmentation
+	if(!last_reserved_address)
+	{
+		last_reserved_address = LLMemory::tryToAlloc(last_reserved_address, MAX_SIZE_CHECKED_MEMORY_BLOCK) ;
+	}
+	else
+	{
+		last_reserved_address = LLMemory::tryToAlloc(last_reserved_address, MAX_SIZE_CHECKED_MEMORY_BLOCK) ;
+		if(!last_reserved_address) //failed, try once more
+		{
+			last_reserved_address = LLMemory::tryToAlloc(last_reserved_address, MAX_SIZE_CHECKED_MEMORY_BLOCK) ;
+		}
+	}
+
+	S32 is_low = !last_reserved_address || LLMemory::isMemoryPoolLow() ;
+
+	//if(is_low < 0) //to force quit
+	//{
+	//	if(force_quit_timer > MAX_QUIT_WAIT_TIME) //just hit the limit for the first time
+	//	{
+	//		//send out the notification to tell the viewer is about to quit in 30 seconds.
+	//		LLNotification::Params params("ForceQuitDueToLowMemory");
+	//		LLNotifications::instance().add(params);
+
+	//		force_quit_timer = MAX_QUIT_WAIT_TIME - MEMORY_CHECK_INTERVAL ;
+	//	}
+	//	else
+	//	{
+	//		force_quit_timer -= MEMORY_CHECK_INTERVAL ;
+	//		if(force_quit_timer < 0.f)
+	//		{
+	//			forceQuit() ; //quit
+	//		}
+	//	}
+	//}
+	//else
+	//{
+	//	force_quit_timer = MAX_QUIT_WAIT_TIME + MEMORY_CHECK_INTERVAL ;
+	//}
+
+	LLPipeline::throttleNewMemoryAllocation(!is_low ? FALSE : TRUE) ;		
+	
+	if(is_low)
+	{
+		LLMemory::logMemoryInfo() ;
+	}
+}
+
 static LLFastTimer::DeclareTimer FTM_MESSAGES("System Messages");
 static LLFastTimer::DeclareTimer FTM_SLEEP("Sleep");
 static LLFastTimer::DeclareTimer FTM_TEXTURE_CACHE("Texture Cache");
@@ -983,8 +1076,7 @@ bool LLAppViewer::mainLoop()
 	LLVoiceChannel::initClass();
 	LLVoiceClient::getInstance()->init(gServicePump);
 	LLTimer frameTimer,idleTimer;
-	LLTimer debugTime;
-	LLFrameTimer memCheckTimer;
+	LLTimer debugTime;	
 	LLViewerJoystick* joystick(LLViewerJoystick::getInstance());
 	joystick->setNeedsReset(true);
 
@@ -993,9 +1085,7 @@ bool LLAppViewer::mainLoop()
     // with each frame, no need to instantiate a new LLSD event object each
     // time. Obviously, if that changes, just instantiate the LLSD at the
     // point of posting.
-    LLSD newFrame;
-
-	const F32 memory_check_interval = 1.0f ; //second
+    LLSD newFrame;	
 
 	// Handle messages
 	while (!LLApp::isExiting())
@@ -1006,18 +1096,8 @@ bool LLAppViewer::mainLoop()
 		llclearcallstacks;
 
 		//check memory availability information
-		{
-			if(memory_check_interval < memCheckTimer.getElapsedTimeF32())
-			{
-				memCheckTimer.reset() ;
-
-				//update the availability of memory
-				LLMemoryInfo::getAvailableMemoryKB(mAvailPhysicalMemInKB, mAvailVirtualMemInKB) ;
-			}
-			llcallstacks << "Available physical mem(KB): " << mAvailPhysicalMemInKB << llcallstacksendl ;
-			llcallstacks << "Available virtual mem(KB): " << mAvailVirtualMemInKB << llcallstacksendl ;
-		}
-
+		checkMemory() ;
+		
 		try
 		{
 			pingMainloopTimeout("Main:MiscNativeWindowEvents");
@@ -1181,7 +1261,7 @@ bool LLAppViewer::mainLoop()
 				idleTimer.reset();
 				bool is_slow = (frameTimer.getElapsedTimeF64() > FRAME_SLOW_THRESHOLD) ;
 				S32 total_work_pending = 0;
-				S32 total_io_pending = 0;				
+				S32 total_io_pending = 0;	
 				while(!is_slow)//do not unpause threads if the frame rates are very low.
 				{
 					S32 work_pending = 0;
@@ -1248,15 +1328,7 @@ bool LLAppViewer::mainLoop()
 		}
 		catch(std::bad_alloc)
 		{			
-			{
-				llinfos << "Availabe physical memory(KB) at the beginning of the frame: " << mAvailPhysicalMemInKB << llendl ;
-				llinfos << "Availabe virtual memory(KB) at the beginning of the frame: " << mAvailVirtualMemInKB << llendl ;
-
-				LLMemoryInfo::getAvailableMemoryKB(mAvailPhysicalMemInKB, mAvailVirtualMemInKB) ;
-
-				llinfos << "Current availabe physical memory(KB): " << mAvailPhysicalMemInKB << llendl ;
-				llinfos << "Current availabe virtual memory(KB): " << mAvailVirtualMemInKB << llendl ;
-			}
+			LLMemory::logMemoryInfo(TRUE) ;
 
 			//stop memory leaking simulation
 			LLFloaterMemLeak* mem_leak_instance =
diff --git a/indra/newview/llappviewer.h b/indra/newview/llappviewer.h
index a70a727c5d..7761a10f1c 100644
--- a/indra/newview/llappviewer.h
+++ b/indra/newview/llappviewer.h
@@ -166,8 +166,8 @@ public:
 	
 	// mute/unmute the system's master audio
 	virtual void setMasterSystemAudioMute(bool mute);
-	virtual bool getMasterSystemAudioMute();
-	
+	virtual bool getMasterSystemAudioMute();	
+
 protected:
 	virtual bool initWindow(); // Initialize the viewer's window.
 	virtual bool initLogging(); // Initialize log files, logging system, return false on failure.
@@ -184,11 +184,12 @@ protected:
 
 private:
 
+	void initMaxHeapSize();
 	bool initThreads(); // Initialize viewer threads, return false on failure.
 	bool initConfiguration(); // Initialize settings from the command line/config file.
 
 	bool initCache(); // Initialize local client cache.
-
+	void checkMemory() ;
 
 	// We have switched locations of both Mac and Windows cache, make sure
 	// files migrate and old cache is cleared out.
@@ -258,8 +259,7 @@ private:
 
 	std::set<struct apr_dso_handle_t*> mPlugins;
 
-	U32 mAvailPhysicalMemInKB ;
-	U32 mAvailVirtualMemInKB ;
+	LLFrameTimer mMemCheckTimer;
 public:
 	//some information for updater
 	typedef struct
diff --git a/indra/newview/lldynamictexture.cpp b/indra/newview/lldynamictexture.cpp
index a3d2941114..58eef45935 100644
--- a/indra/newview/lldynamictexture.cpp
+++ b/indra/newview/lldynamictexture.cpp
@@ -40,6 +40,7 @@
 #include "llvertexbuffer.h"
 #include "llviewerdisplay.h"
 #include "llrender.h"
+#include "pipeline.h"
 
 // static
 LLViewerDynamicTexture::instance_list_t LLViewerDynamicTexture::sInstances[ LLViewerDynamicTexture::ORDER_COUNT ];
@@ -205,7 +206,7 @@ void LLViewerDynamicTexture::postRender(BOOL success)
 BOOL LLViewerDynamicTexture::updateAllInstances()
 {
 	sNumRenders = 0;
-	if (gGLManager.mIsDisabled)
+	if (gGLManager.mIsDisabled || LLPipeline::sMemAllocationThrottled)
 	{
 		return TRUE;
 	}
@@ -221,9 +222,8 @@ BOOL LLViewerDynamicTexture::updateAllInstances()
 			if (dynamicTexture->needsRender())
 			{				
 				if(gGLManager.mDebugGPU)
-				{				
+				{			
 					llinfos << "class type: " << (S32)dynamicTexture->getType() << llendl;
-					LLGLState::dumpStates() ;
 				}
 
 				glClear(GL_DEPTH_BUFFER_BIT);
diff --git a/indra/newview/llfloatermemleak.cpp b/indra/newview/llfloatermemleak.cpp
index 58931d112e..9edfe1e354 100644
--- a/indra/newview/llfloatermemleak.cpp
+++ b/indra/newview/llfloatermemleak.cpp
@@ -90,6 +90,11 @@ LLFloaterMemLeak::~LLFloaterMemLeak()
 
 void LLFloaterMemLeak::release()
 {
+	if(mLeakedMem.empty())
+	{
+		return ;
+	}
+
 	for(S32 i = 0 ; i < (S32)mLeakedMem.size() ; i++)
 	{
 		delete[] mLeakedMem[i] ;
diff --git a/indra/newview/llviewerdisplay.cpp b/indra/newview/llviewerdisplay.cpp
index 7c8b52d0b6..e7153f7ffc 100644
--- a/indra/newview/llviewerdisplay.cpp
+++ b/indra/newview/llviewerdisplay.cpp
@@ -202,6 +202,7 @@ void display_stats()
 		gMemoryAllocated = LLMemory::getCurrentRSS();
 		U32 memory = (U32)(gMemoryAllocated / (1024*1024));
 		llinfos << llformat("MEMORY: %d MB", memory) << llendl;
+		LLMemory::logMemoryInfo() ;
 		gRecentMemoryTime.reset();
 	}
 }
@@ -672,7 +673,11 @@ void display(BOOL rebuild, F32 zoom_factor, int subfield, BOOL for_snapshot)
 				glh::matrix4f mod = glh_get_current_modelview();
 				glViewport(0,0,512,512);
 				LLVOAvatar::updateFreezeCounter() ;
-				LLVOAvatar::updateImpostors();
+
+				if(!LLPipeline::sMemAllocationThrottled)
+				{		
+					LLVOAvatar::updateImpostors();
+				}
 
 				glh_set_current_projection(proj);
 				glh_set_current_modelview(mod);
diff --git a/indra/newview/llviewertexture.cpp b/indra/newview/llviewertexture.cpp
index f96b93da4d..260023a802 100644
--- a/indra/newview/llviewertexture.cpp
+++ b/indra/newview/llviewertexture.cpp
@@ -3068,9 +3068,16 @@ void LLViewerLODTexture::processTextureStats()
 	{
 		mDesiredDiscardLevel = llmin(mDesiredDiscardLevel, (S8)mDesiredSavedRawDiscardLevel) ;
 	}
+	else if(LLPipeline::sMemAllocationThrottled)//release memory of large textures by decrease their resolutions.
+	{
+		if(scaleDown())
+		{
+			mDesiredDiscardLevel = mCachedRawDiscardLevel ;
+		}
+	}
 }
 
-void LLViewerLODTexture::scaleDown()
+bool LLViewerLODTexture::scaleDown()
 {
 	if(hasGLTexture() && mCachedRawDiscardLevel > getDiscardLevel())
 	{		
@@ -3080,7 +3087,10 @@ void LLViewerLODTexture::scaleDown()
 		{
 			LLViewerTextureManager::sTesterp->setStablizingTime() ;
 		}
+
+		return true ;
 	}
+	return false ;
 }
 //----------------------------------------------------------------------------------------------
 //end of LLViewerLODTexture
diff --git a/indra/newview/llviewertexture.h b/indra/newview/llviewertexture.h
index b779396293..ffcbba3efd 100644
--- a/indra/newview/llviewertexture.h
+++ b/indra/newview/llviewertexture.h
@@ -595,7 +595,7 @@ public:
 
 private:
 	void init(bool firstinit) ;
-	void scaleDown() ;		
+	bool scaleDown() ;		
 
 private:
 	F32 mDiscardVirtualSize;		// Virtual size used to calculate desired discard	
diff --git a/indra/newview/llviewerwindow.cpp b/indra/newview/llviewerwindow.cpp
index 64698ed006..943b5b5886 100644
--- a/indra/newview/llviewerwindow.cpp
+++ b/indra/newview/llviewerwindow.cpp
@@ -3874,6 +3874,19 @@ BOOL LLViewerWindow::rawSnapshot(LLImageRaw *raw, S32 image_width, S32 image_hei
 	{
 		return FALSE;
 	}
+	//check if there is enough memory for the snapshot image
+	if(LLPipeline::sMemAllocationThrottled)
+	{
+		return FALSE ; //snapshot taking is disabled due to memory restriction.
+	}
+	if(image_width * image_height > (1 << 22)) //if snapshot image is larger than 2K by 2K
+	{
+		if(!LLMemory::tryToAlloc(NULL, image_width * image_height * 3))
+		{
+			llwarns << "No enough memory to take the snapshot with size (w : h): " << image_width << " : " << image_height << llendl ;
+			return FALSE ; //there is no enough memory for taking this snapshot.
+		}
+	}
 
 	// PRE SNAPSHOT
 	gDisplaySwapBuffers = FALSE;
diff --git a/indra/newview/pipeline.cpp b/indra/newview/pipeline.cpp
index b4a5777f10..7c69af17f2 100644
--- a/indra/newview/pipeline.cpp
+++ b/indra/newview/pipeline.cpp
@@ -98,6 +98,7 @@
 #include "llspatialpartition.h"
 #include "llmutelist.h"
 #include "lltoolpie.h"
+#include "llnotifications.h"
 
 
 #ifdef _DEBUG
@@ -281,6 +282,7 @@ BOOL	LLPipeline::sRenderAttachedLights = TRUE;
 BOOL	LLPipeline::sRenderAttachedParticles = TRUE;
 BOOL	LLPipeline::sRenderDeferred = FALSE;
 BOOL    LLPipeline::sAllowRebuildPriorityGroup = FALSE ;
+BOOL    LLPipeline::sMemAllocationThrottled = FALSE;
 S32		LLPipeline::sVisibleLightCount = 0;
 F32		LLPipeline::sMinRenderSize = 0.f;
 
@@ -513,6 +515,24 @@ void LLPipeline::destroyGL()
 
 static LLFastTimer::DeclareTimer FTM_RESIZE_SCREEN_TEXTURE("Resize Screen Texture");
 
+//static
+void LLPipeline::throttleNewMemoryAllocation(BOOL disable)
+{
+	if(sMemAllocationThrottled != disable)
+	{
+		sMemAllocationThrottled = disable ;
+
+		if(sMemAllocationThrottled)
+		{
+			//send out notification
+			LLNotification::Params params("LowMemory");
+			LLNotifications::instance().add(params);
+
+			//release some memory.
+		}
+	}
+}
+
 void LLPipeline::resizeScreenTexture()
 {
 	LLFastTimer ft(FTM_RESIZE_SCREEN_TEXTURE);
@@ -8792,7 +8812,7 @@ void LLPipeline::renderGroups(LLRenderPass* pass, U32 type, U32 mask, BOOL textu
 
 void LLPipeline::generateImpostor(LLVOAvatar* avatar)
 {
-	LLMemType mt_gi(LLMemType::MTYPE_PIPELINE_GENERATE_IMPOSTOR);
+	LLMemType mt_gi(LLMemType::MTYPE_PIPELINE_GENERATE_IMPOSTOR);	
 	LLGLState::checkStates();
 	LLGLState::checkTextureChannels();
 	LLGLState::checkClientArrays();
diff --git a/indra/newview/pipeline.h b/indra/newview/pipeline.h
index b80765dac6..f4a7dfd38d 100644
--- a/indra/newview/pipeline.h
+++ b/indra/newview/pipeline.h
@@ -334,6 +334,8 @@ public:
 
 	static void updateRenderDeferred();
 
+	static void throttleNewMemoryAllocation(BOOL disable);
+
 private:
 	void unloadShaders();
 	void addToQuickLookup( LLDrawPool* new_poolp );
@@ -477,8 +479,9 @@ public:
 	static BOOL				sRenderAttachedParticles;
 	static BOOL				sRenderDeferred;
 	static BOOL             sAllowRebuildPriorityGroup;
+	static BOOL             sMemAllocationThrottled;
 	static S32				sVisibleLightCount;
-	static F32				sMinRenderSize;
+	static F32				sMinRenderSize;	
 
 	//screen texture
 	U32 					mScreenWidth;
diff --git a/indra/newview/skins/default/xui/en/notifications.xml b/indra/newview/skins/default/xui/en/notifications.xml
index dfbb408d96..5183788c98 100644
--- a/indra/newview/skins/default/xui/en/notifications.xml
+++ b/indra/newview/skins/default/xui/en/notifications.xml
@@ -6451,6 +6451,20 @@ Mute everyone?
   </notification>
 
   <notification
+   icon="alertmodal.tga"
+   name="LowMemory"
+   type="alertmodal">
+    Your memory pool is low. Some functions of SL are disabled to avoid crash. Please close other applications. Restart SL if this persists.
+  </notification>
+
+  <notification
+     icon="alertmodal.tga"
+     name="ForceQuitDueToLowMemory"
+     type="alertmodal">
+    SL will quit in 30 seconds due to out of memory.
+  </notification>
+  
+  <notification
   name="PopupAttempt"
   icon="Popup_Caution"
   type="browser">
@@ -6504,4 +6518,4 @@ Otherwise, you can look at the Map and find places marked &quot;Infohub&quot;.
 You died and have been teleported to your home location.
   </global>
 
-</notifications>
+</notifications>
\ No newline at end of file