gecko/xpcom/ds/nsRecyclingAllocator.cpp
2011-10-17 10:59:28 -04:00

331 lines
9.7 KiB
C++

/* -*- 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 "nsIMemory.h"
#include "prprf.h"
#include "nsITimer.h"
using namespace mozilla;
#define NS_SEC_TO_MS(s) ((s) * 1000)
void
nsRecyclingAllocator::nsRecycleTimerCallback(nsITimer *aTimer, void *aClosure)
{
nsRecyclingAllocator *obj = (nsRecyclingAllocator *) aClosure;
MutexAutoLock lock(obj->mLock);
if (!obj->mTouched)
{
obj->ClearFreeList();
}
else
{
// Clear touched so the next time the timer fires we can test whether
// the allocator was used or not.
obj->mTouched = false;
}
}
nsRecyclingAllocator::nsRecyclingAllocator(PRUint32 nbucket, PRUint32 recycleAfter, const char *id) :
mMaxBlocks(nbucket), mFreeListCount(0), mFreeList(nsnull),
mLock("nsRecyclingAllocator.mLock"),
mRecycleTimer(nsnull), mRecycleAfter(recycleAfter), mTouched(false)
#ifdef DEBUG
, mId(id), mNAllocated(0)
#endif
{
}
nsresult
nsRecyclingAllocator::Init(PRUint32 nbucket, PRUint32 recycleAfter, const char *id)
{
MutexAutoLock lock(mLock);
ClearFreeList();
// Reinitialize everything
mMaxBlocks = nbucket;
mRecycleAfter = recycleAfter;
#ifdef DEBUG
mId = id;
#endif
return NS_OK;
}
nsRecyclingAllocator::~nsRecyclingAllocator()
{
ClearFreeList();
}
// Allocation and free routines
void*
nsRecyclingAllocator::Malloc(PRSize bytes, bool zeroit)
{
// We don't 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
// there are no free blocks, we don't want to impose any more overhead than
// we already are for failing over to malloc/free.
if (mFreeList) {
MutexAutoLock lock(mLock);
// Mark that we are using. This will prevent any
// Timer based release of unused memory.
mTouched = true;
Block* freeNode = mFreeList;
Block** prevp = &mFreeList;
while (freeNode)
{
if (freeNode->bytes >= bytes)
{
// Found the best fit free block
// Remove this block from free list
*prevp = freeNode->next;
mFreeListCount --;
void *data = DATA(freeNode);
if (zeroit)
memset(data, 0, bytes);
return data;
}
prevp = &(freeNode->next);
freeNode = freeNode->next;
}
}
// We need to do an allocation
// Add 4 bytes to what we allocate to hold the bucket index
PRSize allocBytes = bytes + NS_ALLOCATOR_OVERHEAD_BYTES;
// Make sure it is big enough to hold the whole block
if (allocBytes < sizeof(Block)) allocBytes = sizeof(Block);
// We don't have that memory already. Allocate.
Block *ptr = (Block *) (zeroit ? calloc(1, allocBytes) : malloc(allocBytes));
// Deal with no memory situation
if (!ptr)
return ptr;
#ifdef DEBUG
mNAllocated++;
#endif
// Store size and return data portion
ptr->bytes = bytes;
return DATA(ptr);
}
void
nsRecyclingAllocator::Free(void *ptr)
{
Block* block = DATA_TO_BLOCK(ptr);
MutexAutoLock lock(mLock);
// Mark that we are using the allocator. This will prevent any
// timer based release of unused memory.
mTouched = true;
// Check on maximum number of blocks to keep in the freelist
if (mFreeListCount < mMaxBlocks) {
// Find the right spot in the sorted list.
Block* freeNode = mFreeList;
Block** 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 = block;
block->next = freeNode;
mFreeListCount ++;
} else {
// 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);
}
// Set up timer for releasing memory for blocks from the freelist.
// If this fails, then we won't have a timer to release unused
// memory. We can live with that. Also, the next Free
// will try again to set the timer.
if (mRecycleAfter && !mRecycleTimer)
{
// known only to stuff in xpcom.
extern nsresult NS_NewTimer(nsITimer* *aResult, nsTimerCallbackFunc aCallback, void *aClosure,
PRUint32 aDelay, PRUint32 aType);
(void) NS_NewTimer(&mRecycleTimer, nsRecycleTimerCallback, this,
NS_SEC_TO_MS(mRecycleAfter),
nsITimer::TYPE_REPEATING_SLACK);
// This can fail during xpcom shutdown
if (!mRecycleTimer)
NS_WARNING("nsRecyclingAllocator: Creating timer failed");
}
}
/* ClearFreeList
*
* Frees any bucket memory that isn't in use
*/
void
nsRecyclingAllocator::ClearFreeList()
{
#ifdef DEBUG_dp
printf("DEBUG: nsRecyclingAllocator(%s) ClearFreeList (%d): ", mId, mFreeListCount);
#endif
// Cancel the timer, because the freelist will be forcefully cleared after this.
// 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 (mRecycleTimer)
{
mRecycleTimer->Cancel();
NS_RELEASE(mRecycleTimer);
}
// We will run through the freelist and free all blocks
Block* node = mFreeList;
while (node)
{
#ifdef DEBUG_dp
printf("%d ", node->bytes);
#endif
Block *next = node->next;
free(node);
node = next;
}
mFreeList = nsnull;
mFreeListCount = 0;
#ifdef DEBUG
mNAllocated = 0;
#endif
#ifdef DEBUG_dp
printf("\n");
#endif
}
// ----------------------------------------------------------------------
// Wrapping the recyling allocator with nsIMemory
// ----------------------------------------------------------------------
// nsIMemory methods
NS_IMPL_THREADSAFE_ISUPPORTS2(nsRecyclingAllocatorImpl, nsIMemory, nsIRecyclingAllocator)
NS_IMETHODIMP_(void *)
nsRecyclingAllocatorImpl::Alloc(PRSize size)
{
return nsRecyclingAllocatorImpl::Malloc(size, 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)
{
return nsRecyclingAllocator::Init((PRUint32) nbuckets, (PRUint32) recycleAfter, id);
}
NS_IMETHODIMP
nsRecyclingAllocatorImpl::HeapMinimize(bool immediate)
{
// XXX Not yet implemented
return NS_ERROR_NOT_IMPLEMENTED;
}
NS_IMETHODIMP
nsRecyclingAllocatorImpl::IsLowMemory(bool *lowmemoryb_ptr)
{
// XXX Not yet implemented
return NS_ERROR_NOT_IMPLEMENTED;
}