nsRecyclingAllocator.h revision 677833bc953b6cb418c701facbdcf4aa18d6c44e
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* Suresh Duddi <dp@netscape.com>
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/*
* nsRecyclingAllocator
*
* This allocator is useful when we cycle through a small set of allocations
* repeatedly with minimal overlap. For eg. something we do for every gif
* file read (or) buffers required for decompression of every file from jar.
*
* What this does is keeps around the first set of memory allocated and
* reuses it subsequently. If all buckets are full, this falls back to
*
* Uses a timer to release all memory allocated if not used for more than
* 10 secs automatically.
*
* Also there is a 4 byte maintenance overhead on every allocation.
*
* This allocator is thread safe.
*
* CAVEATS: As the number of buckets increases, this allocators performance
* will drop. As a general guideline, dont use this for more
* than NS_MAX_BLOCKS
*/
#ifndef nsRecyclingAllocator_h__
#define nsRecyclingAllocator_h__
#include "nscore.h"
#include "pratom.h"
#include "prlock.h"
#include "nsIRecyclingAllocator.h"
#include "nsIGenericFactory.h"
#define NS_MAX_BLOCKS 24
struct Block {
};
// Make |BlockStoreNode| a |friend| so it can access |Block|.
struct BlockStoreNode;
friend struct BlockStoreNode;
struct BlockStoreNode {
};
// mMaxBlocks: Maximum number of blocks that can be allocated
// mBlocks:
// All blocks used or not.
// mFreeList
// A linked list of free blocks sorted by increasing order of size
// mNotUsedList
// A linked list of BlockStoreNodes that are not used to store
// any block information. When we add blocks into mFreeList, we
// take BlockStoreNode from here.
// mLock: Thread safety of mFreeList and mNotUsedList
// Timer for freeing unused memory
// mRecycleAfter:
// Allocator should be untouched for this many seconds for freeing
// unused Blocks.
// mTouched:
// says if the allocator touched any bucket. If allocator didn't touch
// any bucket over a time time interval, timer will call FreeUnusedBuckets()
// mId:
// a string for identifying the user of nsRecyclingAllocator
// User mainly for debug prints
const char *mId;
#ifdef DEBUG
// mNAllocated: Number of blocks allocated
#endif
// nbucket : number of buckets to hold. Capped at NS_MAX_BUCKET
// recycleAfter : Try recycling allocated buckets after this many seconds
// id : a string used to identify debug prints. Will not be released.
// Allocation and free routines
{
}
// FreeUnusedBuckets - Frees any bucket memory that isn't in use
void FreeUnusedBuckets();
// Timer callback to trigger unused memory
// Freelist management
// FindFreeBlock: return a free block that can hold bytes (best fit)
// AddToFreeList: adds block into our freelist for future retrieval.
// Returns PR_TRUE is addition was successful. PR_FALSE otherewise.
// Touch will mark that someone used this allocator
// Timer based release will free unused memory only if allocator
// was not touched for mRecycleAfter seconds.
void Touch() {
if (!mTouched)
}
void Untouch() {
PR_AtomicSet(&mTouched, 0);
}
};
// ----------------------------------------------------------------------
// Wrapping the recyling allocator with nsIMemory
// ----------------------------------------------------------------------
// Wrapping the nsRecyclingAllocator with nsIMemory
{
}
~nsRecyclingAllocatorImpl() {}
};
#endif // nsRecyclingAllocator_h__