pjs/xpcom/ds/nsRecyclingAllocator.cpp

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/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (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.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* 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 is mozilla.org code.
*
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 2001, 2002
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Suresh Duddi <dp@netscape.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
/*
* nsRecyclingAllocator
*/
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include "nsRecyclingAllocator.h"
#include "nsITimer.h"
#include "nsIMemory.h"
#include "nsAutoLock.h"
#include "prprf.h"
#define NS_SEC_TO_MS(s) ((s) * 1000)
void
nsRecyclingAllocator::nsRecycleTimerCallback(nsITimer *aTimer, void *aClosure)
{
nsRecyclingAllocator *obj = (nsRecyclingAllocator *) aClosure;
if (!obj->mTouched)
{
if (obj->mFreeList)
obj->FreeUnusedBuckets();
// If we are holding no more memory, there is no need for the timer.
// We will revive the timer on the next allocation.
// XXX Unfortunately there is no way to Cancel and restart the same timer.
// XXX So we pretty much kill it and create a new one later.
if (!obj->mFreeList && obj->mRecycleTimer)
{
obj->mRecycleTimer->Cancel();
NS_RELEASE(obj->mRecycleTimer);
}
}
else
{
// Clear touched so the next time the timer fires we can test whether
// the allocator was used or not.
obj->Untouch();
}
}
nsRecyclingAllocator::nsRecyclingAllocator(PRUint32 nbucket, PRUint32 recycleAfter, const char *id) :
mMaxBlocks(nbucket), mBlocks(nsnull), mFreeList(nsnull), mNotUsedList(nsnull),
mRecycleTimer(nsnull), mRecycleAfter(recycleAfter), mTouched(0), mId(id)
#ifdef DEBUG
,mNAllocated(0)
#endif
{
NS_ASSERTION(mMaxBlocks <= NS_MAX_BLOCKS, "Too many blocks. This will affect the allocator's performance.");
mLock = PR_NewLock();
NS_ASSERTION(mLock, "Recycling allocator cannot get lock");
Init(nbucket, recycleAfter, id);
}
NS_IMETHODIMP
nsRecyclingAllocator::Init(PRUint32 nbucket, PRUint32 recycleAfter, const char *id)
{
nsAutoLock lock(mLock);
// Free all memory held, if any
while(mFreeList)
{
free(mFreeList->block);
mFreeList = mFreeList->next;
}
mFreeList = nsnull;
if (mBlocks)
delete [] mBlocks;
// Reinitialize everything
mMaxBlocks = nbucket;
if (nbucket)
{
// Create memory for our bookkeeping
mBlocks = new BlockStoreNode[mMaxBlocks];
if (!mBlocks)
return NS_ERROR_OUT_OF_MEMORY;
// Link them together
mNotUsedList = mBlocks;
for (PRUint32 i=0; i < mMaxBlocks-1; i++)
mBlocks[i].next = &(mBlocks[i+1]);
}
mRecycleAfter = recycleAfter;
mId = id;
return NS_OK;
}
nsRecyclingAllocator::~nsRecyclingAllocator()
{
// Cancel and destroy recycle timer
if (mRecycleTimer)
{
mRecycleTimer->Cancel();
NS_RELEASE(mRecycleTimer);
}
// Free all memory held, if any
while(mFreeList)
{
free(mFreeList->block);
mFreeList = mFreeList->next;
}
mFreeList = nsnull;
if (mBlocks)
delete [] mBlocks;
if (mLock)
{
PR_DestroyLock(mLock);
mLock = nsnull;
}
}
// Allocation and free routines
void*
nsRecyclingAllocator::Malloc(PRUint32 bytes, PRBool zeroit)
{
// Mark that we are using. This will prevent any
// timer based release of unused memory.
Touch();
Block* freeBlock = FindFreeBlock(bytes);
if (freeBlock)
{
return DATA(freeBlock);
}
// We need to do an allocation
// Add 4 bytes to what we allocate to hold the bucket index
PRUint32 allocBytes = bytes + NS_ALLOCATOR_OVERHEAD_BYTES;
// We dont have that memory already. Allocate.
Block *ptr = (Block *) (zeroit ? calloc(1, allocBytes) : malloc(allocBytes));
// Deal with no memory situation
if (!ptr)
return ptr;
// This is the first allocation we are holding.
// Setup timer for releasing memory
// If this fails, then we wont have a timer to release unused
// memory. We can live with that. Also, the next allocation
// will try again to set the timer.
if (mRecycleAfter && !mRecycleTimer)
{
(void) NS_NewTimer(&mRecycleTimer, nsRecycleTimerCallback, this,
NS_SEC_TO_MS(mRecycleAfter), PR_TRUE,
NS_TYPE_REPEATING_SLACK);
NS_ASSERTION(mRecycleTimer, "nsRecyclingAllocator: Creating timer failed.\n");
}
#ifdef DEBUG
mNAllocated++;
#endif
// Store size and return data portion
ptr->bytes = bytes;
return DATA(ptr);
}
void
nsRecyclingAllocator::Free(void *ptr)
{
// Mark that we are using the allocator. This will prevent any
// timer based release of unused memory.
Touch();
Block* block = DATA_TO_BLOCK(ptr);
if (!AddToFreeList(block))
{
// We are holding more than max. Failover to free
#ifdef DEBUG_dp
char buf[1024];
// Warn if we are failing over to malloc/free and not storing it
// This says we have a misdesigned memory pool. The intent was
// once the pool was full, we would never fail over to calloc.
PR_snprintf(buf, sizeof(buf), "nsRecyclingAllocator(%s) FAILOVER 0x%p (%d) - %d allocations, %d max\n",
mId, (char *)ptr, block->bytes, mNAllocated, mMaxBlocks);
NS_WARNING(buf);
mNAllocated--;
#endif
free(block);
}
}
/* FreeUnusedBuckets
*
* Frees any bucket memory that isn't in use
*/
void
nsRecyclingAllocator::FreeUnusedBuckets()
{
#ifdef DEBUG_dp
printf("DEBUG: nsRecyclingAllocator(%s) FreeUnusedBuckets: ", mId);
#endif
nsAutoLock lock(mLock);
// We will run through the freelist and free all blocks
BlockStoreNode* node = mFreeList;
while (node)
{
// Free the allocated block
free(node->block);
#ifdef DEBUG_dp
printf("%d ", node->bytes);
#endif
// Clear Node
node->block = nsnull;
node->bytes = 0;
node = node->next;
}
// remake the lists
mNotUsedList = mBlocks;
for (PRUint32 i=0; i < mMaxBlocks-1; i++)
mBlocks[i].next = &(mBlocks[i+1]);
mBlocks[mMaxBlocks-1].next = nsnull;
mFreeList = nsnull;
#ifdef DEBUG
mNAllocated = 0;
#endif
#ifdef DEBUG_dp
printf("\n");
#endif
}
inline nsRecyclingAllocator::Block*
nsRecyclingAllocator::FindFreeBlock(PRUint32 bytes)
{
// We dont enter lock for this check. This is intentional.
// Here is my logic: we are checking if (!mFreeList). Doing this check
// without locking can lead to unpredictable results. YES. But the effect
// of the unpredictedness are ok. here is why:
//
// a) if the check returned NULL when there is stuff in freelist
// We would just end up reallocating.
//
// b) if the check returned nonNULL when our freelist is empty
// This is the more likely and dangerous case. The code for
// FindFreeBlock() will enter lock, while (null) and return null.
//
// The reason why I chose to not enter lock for this check was that when
// the allocator is full, we dont want to impose any more overhead than
// we already are for failing over to malloc/free.
if (!mFreeList)
return NULL;
Block *block = nsnull;
nsAutoLock lock(mLock);
BlockStoreNode* freeNode = mFreeList;
BlockStoreNode** prevp = &mFreeList;
while (freeNode)
{
if (freeNode->bytes >= bytes)
{
// Found the best fit free block
block = freeNode->block;
// Clear the free node
freeNode->block = nsnull;
freeNode->bytes = 0;
// Remove free node from free list
*prevp = freeNode->next;
// Add removed BlockStoreNode to not used list
freeNode->next = mNotUsedList;
mNotUsedList = freeNode;
break;
}
prevp = &(freeNode->next);
freeNode = freeNode->next;
}
return block;
}
inline PRInt32
nsRecyclingAllocator::AddToFreeList(Block* block)
{
// Make sure we arent keeping more than mMaxBlocks
if (!mNotUsedList)
return PR_FALSE;
nsAutoLock lock(mLock);
// Pick a node from the not used list
BlockStoreNode *node = mNotUsedList;
mNotUsedList = mNotUsedList->next;
// Initialize the node
node->bytes = block->bytes;
node->block = block;
// Find the right spot in the sorted list.
BlockStoreNode* freeNode = mFreeList;
BlockStoreNode** prevp = &mFreeList;
while (freeNode)
{
if (freeNode->bytes >= block->bytes)
break;
prevp = &(freeNode->next);
freeNode = freeNode->next;
}
// Needs to be inserted between *prevp and freeNode
*prevp = node;
node->next = freeNode;
return PR_TRUE;
}
// ----------------------------------------------------------------------
// Wrapping the recyling allocator with nsIMemory
// ----------------------------------------------------------------------
// nsIMemory methods
NS_IMPL_THREADSAFE_ISUPPORTS2(nsRecyclingAllocatorImpl, nsIMemory, nsIRecyclingAllocator);
NS_IMETHODIMP_(void *)
nsRecyclingAllocatorImpl::Alloc(PRSize size)
{
if (size < 0)
return NULL;
else
return nsRecyclingAllocatorImpl::Malloc(size, PR_FALSE);
}
NS_IMETHODIMP_(void *)
nsRecyclingAllocatorImpl::Realloc(void *ptr, PRSize size)
{
// XXX Not yet implemented
return NULL;
}
NS_IMETHODIMP_(void)
nsRecyclingAllocatorImpl::Free(void *ptr)
{
nsRecyclingAllocator::Free(ptr);
}
NS_IMETHODIMP
nsRecyclingAllocatorImpl::Init(size_t nbuckets, size_t recycleAfter, const char *id)
{
// normalize input
if (nbuckets < 0)
nbuckets = 0;
if (recycleAfter < 0)
recycleAfter = 0;
return nsRecyclingAllocator::Init((PRUint32) nbuckets, (PRUint32) recycleAfter, id);
}
NS_IMETHODIMP
nsRecyclingAllocatorImpl::HeapMinimize(PRBool immediate)
{
// XXX Not yet implemented
return NS_ERROR_NOT_IMPLEMENTED;
}
NS_IMETHODIMP
nsRecyclingAllocatorImpl::IsLowMemory(PRBool *lowmemoryb_ptr)
{
// XXX Not yet implemented
return NS_ERROR_NOT_IMPLEMENTED;
}