/*
* tclAlloc.c --
*
* This is a very fast storage allocator. It allocates blocks of a small
* number of different sizes, and keeps free lists of each size. Blocks
* that don't exactly fit are passed up to the next larger size. Blocks
* over a certain size are directly allocated from the system.
*
* Copyright (c) 1983 Regents of the University of California.
* Copyright (c) 1996-1997 Sun Microsystems, Inc.
* Copyright (c) 1998-1999 by Scriptics Corporation.
*
* Portions contributed by Chris Kingsley, Jack Jansen and Ray Johnson.
*
* See the file "license.terms" for information on usage and redistribution of
* this file, and for a DISCLAIMER OF ALL WARRANTIES.
*
* RCS: @(#) $Id: tclAlloc.c,v 1.27.2.1 2009/09/29 04:43:58 dgp Exp $
*/
/*
* Windows and Unix use an alternative allocator when building with threads
* that has significantly reduced lock contention.
*/
#include "tclInt.h"
#if !defined(TCL_THREADS) || !defined(USE_THREAD_ALLOC)
#if USE_TCLALLOC
#ifdef TCL_DEBUG
# define DEBUG
/* #define MSTATS */
# define RCHECK
#endif
/*
* We should really make use of AC_CHECK_TYPE(caddr_t) here, but it can wait
* until Tcl uses config.h properly.
*/
#if defined(_MSC_VER) || defined(__MINGW32__) || defined(__BORLANDC__)
typedef unsigned long caddr_t;
#endif
/*
* The overhead on a block is at least 8 bytes. When free, this space contains
* a pointer to the next free block, and the bottom two bits must be zero.
* When in use, the first byte is set to MAGIC, and the second byte is the
* size index. The remaining bytes are for alignment. If range checking is
* enabled then a second word holds the size of the requested block, less 1,
* rounded up to a multiple of sizeof(RMAGIC). The order of elements is
* critical: ov.magic must overlay the low order bits of ov.next, and ov.magic
* can not be a valid ov.next bit pattern.
*/
union overhead {
union overhead *next; /* when free */
unsigned char padding[TCL_ALLOCALIGN]; /* align struct to TCL_ALLOCALIGN bytes */
struct {
unsigned char magic0; /* magic number */
unsigned char index; /* bucket # */
unsigned char unused; /* unused */
unsigned char magic1; /* other magic number */
#ifdef RCHECK
unsigned short rmagic; /* range magic number */
unsigned long size; /* actual block size */
unsigned short unused2; /* padding to 8-byte align */
#endif
} ovu;
#define overMagic0 ovu.magic0
#define overMagic1 ovu.magic1
#define bucketIndex ovu.index
#define rangeCheckMagic ovu.rmagic
#define realBlockSize ovu.size
};
#define MAGIC 0xef /* magic # on accounting info */
#define RMAGIC 0x5555 /* magic # on range info */
#ifdef RCHECK
#define RSLOP sizeof (unsigned short)
#else
#define RSLOP 0
#endif
#define OVERHEAD (sizeof(union overhead) + RSLOP)
/*
* Macro to make it easier to refer to the end-of-block guard magic.
*/
#define BLOCK_END(overPtr) \
(*(unsigned short *)((caddr_t)((overPtr) + 1) + (overPtr)->realBlockSize))
/*
* nextf[i] is the pointer to the next free block of size 2^(i+3). The
* smallest allocatable block is MINBLOCK bytes. The overhead information
* precedes the data area returned to the user.
*/
#define MINBLOCK ((sizeof(union overhead) + (TCL_ALLOCALIGN-1)) & ~(TCL_ALLOCALIGN-1))
#define NBUCKETS (13 - (MINBLOCK >> 4))
#define MAXMALLOC (1<<(NBUCKETS+2))
static union overhead *nextf[NBUCKETS];
/*
* The following structure is used to keep track of all system memory
* currently owned by Tcl. When finalizing, all this memory will be returned
* to the system.
*/
struct block {
struct block *nextPtr; /* Linked list. */
struct block *prevPtr; /* Linked list for big blocks, ensures 8-byte
* alignment for suballocated blocks. */
};
static struct block *blockList; /* Tracks the suballocated blocks. */
static struct block bigBlocks={ /* Big blocks aren't suballocated. */
&bigBlocks, &bigBlocks
};
/*
* The allocator is protected by a special mutex that must be explicitly
* initialized. Futhermore, because Tcl_Alloc may be used before anything else
* in Tcl, we make this module self-initializing after all with the allocInit
* variable.
*/
#ifdef TCL_THREADS
static Tcl_Mutex *allocMutexPtr;
#endif
static int allocInit = 0;
#ifdef MSTATS
/*
* numMallocs[i] is the difference between the number of mallocs and frees for
* a given block size.
*/
static unsigned int numMallocs[NBUCKETS+1];
#include <stdio.h>
#endif
#if defined(DEBUG) || defined(RCHECK)
#define ASSERT(p) if (!(p)) Tcl_Panic(# p)
#define RANGE_ASSERT(p) if (!(p)) Tcl_Panic(# p)
#else
#define ASSERT(p)
#define RANGE_ASSERT(p)
#endif
/*
* Prototypes for functions used only in this file.
*/
static void MoreCore(int bucket);
/*
*-------------------------------------------------------------------------
*
* TclInitAlloc --
*
* Initialize the memory system.
*
* Results:
* None.
*
* Side effects:
* Initialize the mutex used to serialize allocations.
*
*-------------------------------------------------------------------------
*/
void
TclInitAlloc(void)
{
if (!allocInit) {
allocInit = 1;
#ifdef TCL_THREADS
allocMutexPtr = Tcl_GetAllocMutex();
#endif
}
}
/*
*-------------------------------------------------------------------------
*
* TclFinalizeAllocSubsystem --
*
* Release all resources being used by this subsystem, including
* aggressively freeing all memory allocated by TclpAlloc() that has not
* yet been released with TclpFree().
*
* After this function is called, all memory allocated with TclpAlloc()
* should be considered unusable.
*
* Results:
* None.
*
* Side effects:
* This subsystem is self-initializing, since memory can be allocated
* before Tcl is formally initialized. After this call, this subsystem
* has been reset to its initial state and is usable again.
*
*-------------------------------------------------------------------------
*/
void
TclFinalizeAllocSubsystem(void)
{
unsigned int i;
struct block *blockPtr, *nextPtr;
Tcl_MutexLock(allocMutexPtr);
for (blockPtr = blockList; blockPtr != NULL; blockPtr = nextPtr) {
nextPtr = blockPtr->nextPtr;
TclpSysFree(blockPtr);
}
blockList = NULL;
for (blockPtr = bigBlocks.nextPtr; blockPtr != &bigBlocks; ) {
nextPtr = blockPtr->nextPtr;
TclpSysFree(blockPtr);
blockPtr = nextPtr;
}
bigBlocks.nextPtr = &bigBlocks;
bigBlocks.prevPtr = &bigBlocks;
for (i=0 ; i<NBUCKETS ; i++) {
nextf[i] = NULL;
#ifdef MSTATS
numMallocs[i] = 0;
#endif
}
#ifdef MSTATS
numMallocs[i] = 0;
#endif
Tcl_MutexUnlock(allocMutexPtr);
}
/*
*----------------------------------------------------------------------
*
* TclpAlloc --
*
* Allocate more memory.
*
* Results:
* None.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
char *
TclpAlloc(
unsigned int numBytes) /* Number of bytes to allocate. */
{
register union overhead *overPtr;
register long bucket;
register unsigned amount;
struct block *bigBlockPtr = NULL;
if (!allocInit) {
/*
* We have to make the "self initializing" because Tcl_Alloc may be
* used before any other part of Tcl. E.g., see main() for tclsh!
*/
TclInitAlloc();
}
Tcl_MutexLock(allocMutexPtr);
/*
* First the simple case: we simple allocate big blocks directly.
*/
if (numBytes >= MAXMALLOC - OVERHEAD) {
if (numBytes <= UINT_MAX - OVERHEAD -sizeof(struct block)) {
bigBlockPtr = (struct block *) TclpSysAlloc((unsigned)
(sizeof(struct block) + OVERHEAD + numBytes), 0);
}
if (bigBlockPtr == NULL) {
Tcl_MutexUnlock(allocMutexPtr);
return NULL;
}
bigBlockPtr->nextPtr = bigBlocks.nextPtr;
bigBlocks.nextPtr = bigBlockPtr;
bigBlockPtr->prevPtr = &bigBlocks;
bigBlockPtr->nextPtr->prevPtr = bigBlockPtr;
overPtr = (union overhead *) (bigBlockPtr + 1);
overPtr->overMagic0 = overPtr->overMagic1 = MAGIC;
overPtr->bucketIndex = 0xff;
#ifdef MSTATS
numMallocs[NBUCKETS]++;
#endif
#ifdef RCHECK
/*
* Record allocated size of block and bound space with magic numbers.
*/
overPtr->realBlockSize = (numBytes + RSLOP - 1) & ~(RSLOP - 1);
overPtr->rangeCheckMagic = RMAGIC;
BLOCK_END(overPtr) = RMAGIC;
#endif
Tcl_MutexUnlock(allocMutexPtr);
return (void *)(overPtr+1);
}
/*
* Convert amount of memory requested into closest block size stored in
* hash buckets which satisfies request. Account for space used per block
* for accounting.
*/
amount = MINBLOCK; /* size of first bucket */
bucket = MINBLOCK >> 4;
while (numBytes + OVERHEAD > amount) {
amount <<= 1;
if (amount == 0) {
Tcl_MutexUnlock(allocMutexPtr);
return NULL;
}
bucket++;
}
ASSERT(bucket < NBUCKETS);
/*
* If nothing in hash bucket right now, request more memory from the
* system.
*/
if ((overPtr = nextf[bucket]) == NULL) {
MoreCore(bucket);
if ((overPtr = nextf[bucket]) == NULL) {
Tcl_MutexUnlock(allocMutexPtr);
return NULL;
}
}
/*
* Remove from linked list
*/
nextf[bucket] = overPtr->next;
overPtr->overMagic0 = overPtr->overMagic1 = MAGIC;
overPtr->bucketIndex = (unsigned char) bucket;
#ifdef MSTATS
numMallocs[bucket]++;
#endif
#ifdef RCHECK
/*
* Record allocated size of block and bound space with magic numbers.
*/
overPtr->realBlockSize = (numBytes + RSLOP - 1) & ~(RSLOP - 1);
overPtr->rangeCheckMagic = RMAGIC;
BLOCK_END(overPtr) = RMAGIC;
#endif
Tcl_MutexUnlock(allocMutexPtr);
return ((char *)(overPtr + 1));
}
/*
*----------------------------------------------------------------------
*
* MoreCore --
*
* Allocate more memory to the indicated bucket.
*
* Assumes Mutex is already held.
*
* Results:
* None.
*
* Side effects:
* Attempts to get more memory from the system.
*
*----------------------------------------------------------------------
*/
static void
MoreCore(
int bucket) /* What bucket to allocat to. */
{
register union overhead *overPtr;
register long size; /* size of desired block */
long amount; /* amount to allocate */
int numBlocks; /* how many blocks we get */
struct block *blockPtr;
/*
* sbrk_size <= 0 only for big, FLUFFY, requests (about 2^30 bytes on a
* VAX, I think) or for a negative arg.
*/
size = 1 << (bucket + 3);
ASSERT(size > 0);
amount = MAXMALLOC;
numBlocks = amount / size;
ASSERT(numBlocks*size == amount);
blockPtr = (struct block *) TclpSysAlloc((unsigned)
(sizeof(struct block) + amount), 1);
/* no more room! */
if (blockPtr == NULL) {
return;
}
blockPtr->nextPtr = blockList;
blockList = blockPtr;
overPtr = (union overhead *) (blockPtr + 1);
/*
* Add new memory allocated to that on free list for this hash bucket.
*/
nextf[bucket] = overPtr;
while (--numBlocks > 0) {
overPtr->next = (union overhead *)((caddr_t)overPtr + size);
overPtr = (union overhead *)((caddr_t)overPtr + size);
}
overPtr->next = NULL;
}
/*
*----------------------------------------------------------------------
*
* TclpFree --
*
* Free memory.
*
* Results:
* None.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
void
TclpFree(
char *oldPtr) /* Pointer to memory to free. */
{
register long size;
register union overhead *overPtr;
struct block *bigBlockPtr;
if (oldPtr == NULL) {
return;
}
Tcl_MutexLock(allocMutexPtr);
overPtr = (union overhead *)((caddr_t)oldPtr - sizeof (union overhead));
ASSERT(overPtr->overMagic0 == MAGIC); /* make sure it was in use */
ASSERT(overPtr->overMagic1 == MAGIC);
if (overPtr->overMagic0 != MAGIC || overPtr->overMagic1 != MAGIC) {
Tcl_MutexUnlock(allocMutexPtr);
return;
}
RANGE_ASSERT(overPtr->rangeCheckMagic == RMAGIC);
RANGE_ASSERT(BLOCK_END(overPtr) == RMAGIC);
size = overPtr->bucketIndex;
if (size == 0xff) {
#ifdef MSTATS
numMallocs[NBUCKETS]--;
#endif
bigBlockPtr = (struct block *) overPtr - 1;
bigBlockPtr->prevPtr->nextPtr = bigBlockPtr->nextPtr;
bigBlockPtr->nextPtr->prevPtr = bigBlockPtr->prevPtr;
TclpSysFree(bigBlockPtr);
Tcl_MutexUnlock(allocMutexPtr);
return;
}
ASSERT(size < NBUCKETS);
overPtr->next = nextf[size]; /* also clobbers overMagic */
nextf[size] = overPtr;
#ifdef MSTATS
numMallocs[size]--;
#endif
Tcl_MutexUnlock(allocMutexPtr);
}
/*
*----------------------------------------------------------------------
*
* TclpRealloc --
*
* Reallocate memory.
*
* Results:
* None.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
char *
TclpRealloc(
char *oldPtr, /* Pointer to alloced block. */
unsigned int numBytes) /* New size of memory. */
{
int i;
union overhead *overPtr;
struct block *bigBlockPtr;
int expensive;
unsigned long maxSize;
if (oldPtr == NULL) {
return TclpAlloc(numBytes);
}
Tcl_MutexLock(allocMutexPtr);
overPtr = (union overhead *)((caddr_t)oldPtr - sizeof (union overhead));
ASSERT(overPtr->overMagic0 == MAGIC); /* make sure it was in use */
ASSERT(overPtr->overMagic1 == MAGIC);
if (overPtr->overMagic0 != MAGIC || overPtr->overMagic1 != MAGIC) {
Tcl_MutexUnlock(allocMutexPtr);
return NULL;
}
RANGE_ASSERT(overPtr->rangeCheckMagic == RMAGIC);
RANGE_ASSERT(BLOCK_END(overPtr) == RMAGIC);
i = overPtr->bucketIndex;
/*
* If the block isn't in a bin, just realloc it.
*/
if (i == 0xff) {
struct block *prevPtr, *nextPtr;
bigBlockPtr = (struct block *) overPtr - 1;
prevPtr = bigBlockPtr->prevPtr;
nextPtr = bigBlockPtr->nextPtr;
bigBlockPtr = (struct block *) TclpSysRealloc(bigBlockPtr,
sizeof(struct block) + OVERHEAD + numBytes);
if (bigBlockPtr == NULL) {
Tcl_MutexUnlock(allocMutexPtr);
return NULL;
}
if (prevPtr->nextPtr != bigBlockPtr) {
/*
* If the block has moved, splice the new block into the list
* where the old block used to be.
*/
prevPtr->nextPtr = bigBlockPtr;
nextPtr->prevPtr = bigBlockPtr;
}
overPtr = (union overhead *) (bigBlockPtr + 1);
#ifdef MSTATS
numMallocs[NBUCKETS]++;
#endif
#ifdef RCHECK
/*
* Record allocated size of block and update magic number bounds.
*/
overPtr->realBlockSize = (numBytes + RSLOP - 1) & ~(RSLOP - 1);
BLOCK_END(overPtr) = RMAGIC;
#endif
Tcl_MutexUnlock(allocMutexPtr);
return (char *)(overPtr+1);
}
maxSize = 1 << (i+3);
expensive = 0;
if (numBytes+OVERHEAD > maxSize) {
expensive = 1;
} else if (i>0 && numBytes+OVERHEAD < maxSize/2) {
expensive = 1;
}
if (expensive) {
void *newPtr;
Tcl_MutexUnlock(allocMutexPtr);
newPtr = TclpAlloc(numBytes);
if (newPtr == NULL) {
return NULL;
}
maxSize -= OVERHEAD;
if (maxSize < numBytes) {
numBytes = maxSize;
}
memcpy(newPtr, oldPtr, (size_t) numBytes);
TclpFree(oldPtr);
return newPtr;
}
/*
* Ok, we don't have to copy, it fits as-is
*/
#ifdef RCHECK
overPtr->realBlockSize = (numBytes + RSLOP - 1) & ~(RSLOP - 1);
BLOCK_END(overPtr) = RMAGIC;
#endif
Tcl_MutexUnlock(allocMutexPtr);
return(oldPtr);
}
/*
*----------------------------------------------------------------------
*
* mstats --
*
* Prints two lines of numbers, one showing the length of the free list
* for each size category, the second showing the number of mallocs -
* frees for each size category.
*
* Results:
* None.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
#ifdef MSTATS
void
mstats(
char *s) /* Where to write info. */
{
register int i, j;
register union overhead *overPtr;
int totalFree = 0, totalUsed = 0;
Tcl_MutexLock(allocMutexPtr);
fprintf(stderr, "Memory allocation statistics %s\nTclpFree:\t", s);
for (i = 0; i < NBUCKETS; i++) {
for (j=0, overPtr=nextf[i]; overPtr; overPtr=overPtr->next, j++) {
fprintf(stderr, " %d", j);
}
totalFree += j * (1 << (i + 3));
}
fprintf(stderr, "\nused:\t");
for (i = 0; i < NBUCKETS; i++) {
fprintf(stderr, " %d", numMallocs[i]);
totalUsed += numMallocs[i] * (1 << (i + 3));
}
fprintf(stderr, "\n\tTotal small in use: %d, total free: %d\n",
totalUsed, totalFree);
fprintf(stderr, "\n\tNumber of big (>%d) blocks in use: %d\n",
MAXMALLOC, numMallocs[NBUCKETS]);
Tcl_MutexUnlock(allocMutexPtr);
}
#endif
#else /* !USE_TCLALLOC */
/*
*----------------------------------------------------------------------
*
* TclpAlloc --
*
* Allocate more memory.
*
* Results:
* None.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
char *
TclpAlloc(
unsigned int numBytes) /* Number of bytes to allocate. */
{
return (char*) malloc(numBytes);
}
/*
*----------------------------------------------------------------------
*
* TclpFree --
*
* Free memory.
*
* Results:
* None.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
void
TclpFree(
char *oldPtr) /* Pointer to memory to free. */
{
free(oldPtr);
return;
}
/*
*----------------------------------------------------------------------
*
* TclpRealloc --
*
* Reallocate memory.
*
* Results:
* None.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
char *
TclpRealloc(
char *oldPtr, /* Pointer to alloced block. */
unsigned int numBytes) /* New size of memory. */
{
return (char*) realloc(oldPtr, numBytes);
}
#endif /* !USE_TCLALLOC */
#endif /* !TCL_THREADS */
/*
* Local Variables:
* mode: c
* c-basic-offset: 4
* fill-column: 78
* End:
*/
|
