/*
* 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 1.16 2002/04/23 17:03:34 hobbs Exp $
*/
/*
* Windows and Unix use an alternative allocator when building with threads
* that has significantly reduced lock contention.
*/
#if !defined(TCL_THREADS) || !defined(USE_THREAD_ALLOC)
#include "tclInt.h"
#include "tclPort.h"
#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(MAC_TCL) || 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 *ov_next; /* when free */
unsigned char ov_padding[8]; /* Ensure the structure is 8-byte aligned. */
struct {
unsigned char ovu_magic0; /* magic number */
unsigned char ovu_index; /* bucket # */
unsigned char ovu_unused; /* unused */
unsigned char ovu_magic1; /* other magic number */
#ifdef RCHECK
unsigned short ovu_rmagic; /* range magic number */
unsigned long ovu_size; /* actual block size */
unsigned short ovu_unused2; /* padding to 8-byte align */
#endif
} ovu;
#define ov_magic0 ovu.ovu_magic0
#define ov_magic1 ovu.ovu_magic1
#define ov_index ovu.ovu_index
#define ov_rmagic ovu.ovu_rmagic
#define ov_size ovu.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)
/*
* nextf[i] is the pointer to the next free block of size 2^(i+3). The
* smallest allocatable block is 8 bytes. The overhead information
* precedes the data area returned to the user.
*/
#define NBUCKETS 13
#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
/*
* nmalloc[i] is the difference between the number of mallocs and frees
* for a given block size.
*/
static unsigned int nmalloc[NBUCKETS+1];
#include <stdio.h>
#endif
#if defined(DEBUG) || defined(RCHECK)
#define ASSERT(p) if (!(p)) panic(# p)
#define RANGE_ASSERT(p) if (!(p)) panic(# p)
#else
#define ASSERT(p)
#define RANGE_ASSERT(p)
#endif
/*
* Prototypes for functions used only in this file.
*/
static void MoreCore _ANSI_ARGS_((int bucket));
/*
*-------------------------------------------------------------------------
*
* TclInitAlloc --
*
* Initialize the memory system.
*
* Results:
* None.
*
* Side effects:
* Initialize the mutex used to serialize allocations.
*
*-------------------------------------------------------------------------
*/
void
TclInitAlloc()
{
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()
{
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
nmalloc[i] = 0;
#endif
}
#ifdef MSTATS
nmalloc[i] = 0;
#endif
Tcl_MutexUnlock(allocMutexPtr);
}
/*
*----------------------------------------------------------------------
*
* TclpAlloc --
*
* Allocate more memory.
*
* Results:
* None.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
char *
TclpAlloc(nbytes)
unsigned int nbytes; /* Number of bytes to allocate. */
{
register union overhead *op;
register long bucket;
register unsigned amt;
struct block *bigBlockPtr;
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 (nbytes + OVERHEAD >= MAXMALLOC) {
bigBlockPtr = (struct block *) TclpSysAlloc((unsigned)
(sizeof(struct block) + OVERHEAD + nbytes), 0);
if (bigBlockPtr == NULL) {
Tcl_MutexUnlock(allocMutexPtr);
return NULL;
}
bigBlockPtr->nextPtr = bigBlocks.nextPtr;
bigBlocks.nextPtr = bigBlockPtr;
bigBlockPtr->prevPtr = &bigBlocks;
bigBlockPtr->nextPtr->prevPtr = bigBlockPtr;
op = (union overhead *) (bigBlockPtr + 1);
op->ov_magic0 = op->ov_magic1 = MAGIC;
op->ov_index = 0xff;
#ifdef MSTATS
nmalloc[NBUCKETS]++;
#endif
#ifdef RCHECK
/*
* Record allocated size of block and
* bound space with magic numbers.
*/
op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
op->ov_rmagic = RMAGIC;
*(unsigned short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
#endif
Tcl_MutexUnlock(allocMutexPtr);
return (void *)(op+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.
*/
#ifndef RCHECK
amt = 8; /* size of first bucket */
bucket = 0;
#else
amt = 16; /* size of first bucket */
bucket = 1;
#endif
while (nbytes + OVERHEAD > amt) {
amt <<= 1;
if (amt == 0) {
Tcl_MutexUnlock(allocMutexPtr);
return (NULL);
}
bucket++;
}
ASSERT( bucket < NBUCKETS );
/*
* If nothing in hash bucket right now,
* request more memory from the system.
*/
if ((op = nextf[bucket]) == NULL) {
MoreCore(bucket);
if ((op = nextf[bucket]) == NULL) {
Tcl_MutexUnlock(allocMutexPtr);
return (NULL);
}
}
/*
* Remove from linked list
*/
nextf[bucket] = op->ov_next;
op->ov_magic0 = op->ov_magic1 = MAGIC;
op->ov_index = (unsigned char) bucket;
#ifdef MSTATS
nmalloc[bucket]++;
#endif
#ifdef RCHECK
/*
* Record allocated size of block and
* bound space with magic numbers.
*/
op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
op->ov_rmagic = RMAGIC;
*(unsigned short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
#endif
Tcl_MutexUnlock(allocMutexPtr);
return ((char *)(op + 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(bucket)
int bucket; /* What bucket to allocat to. */
{
register union overhead *op;
register long sz; /* size of desired block */
long amt; /* amount to allocate */
int nblks; /* 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.
*/
sz = 1 << (bucket + 3);
ASSERT(sz > 0);
amt = MAXMALLOC;
nblks = amt / sz;
ASSERT(nblks*sz == amt);
blockPtr = (struct block *) TclpSysAlloc((unsigned)
(sizeof(struct block) + amt), 1);
/* no more room! */
if (blockPtr == NULL) {
return;
}
blockPtr->nextPtr = blockList;
blockList = blockPtr;
op = (union overhead *) (blockPtr + 1);
/*
* Add new memory allocated to that on
* free list for this hash bucket.
*/
nextf[bucket] = op;
while (--nblks > 0) {
op->ov_next = (union overhead *)((caddr_t)op + sz);
op = (union overhead *)((caddr_t)op + sz);
}
op->ov_next = (union overhead *)NULL;
}
/*
*----------------------------------------------------------------------
*
* TclpFree --
*
* Free memory.
*
* Results:
* None.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
void
TclpFree(cp)
char *cp; /* Pointer to memory to free. */
{
register long size;
register union overhead *op;
struct block *bigBlockPtr;
if (cp == NULL) {
return;
}
Tcl_MutexLock(allocMutexPtr);
op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
ASSERT(op->ov_magic0 == MAGIC); /* make sure it was in use */
ASSERT(op->ov_magic1 == MAGIC);
if (op->ov_magic0 != MAGIC || op->ov_magic1 != MAGIC) {
Tcl_MutexUnlock(allocMutexPtr);
return;
}
RANGE_ASSERT(op->ov_rmagic == RMAGIC);
RANGE_ASSERT(*(unsigned short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
size = op->ov_index;
if ( size == 0xff ) {
#ifdef MSTATS
nmalloc[NBUCKETS]--;
#endif
bigBlockPtr = (struct block *) op - 1;
bigBlockPtr->prevPtr->nextPtr = bigBlockPtr->nextPtr;
bigBlockPtr->nextPtr->prevPtr = bigBlockPtr->prevPtr;
TclpSysFree(bigBlockPtr);
Tcl_MutexUnlock(allocMutexPtr);
return;
}
ASSERT(size < NBUCKETS);
op->ov_next = nextf[size]; /* also clobbers ov_magic */
nextf[size] = op;
#ifdef MSTATS
nmalloc[size]--;
#endif
Tcl_MutexUnlock(allocMutexPtr);
}
/*
*----------------------------------------------------------------------
*
* TclpRealloc --
*
* Reallocate memory.
*
* Results:
* None.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
char *
TclpRealloc(cp, nbytes)
char *cp; /* Pointer to alloced block. */
unsigned int nbytes; /* New size of memory. */
{
int i;
union overhead *op;
struct block *bigBlockPtr;
int expensive;
unsigned long maxsize;
if (cp == NULL) {
return (TclpAlloc(nbytes));
}
Tcl_MutexLock(allocMutexPtr);
op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
ASSERT(op->ov_magic0 == MAGIC); /* make sure it was in use */
ASSERT(op->ov_magic1 == MAGIC);
if (op->ov_magic0 != MAGIC || op->ov_magic1 != MAGIC) {
Tcl_MutexUnlock(allocMutexPtr);
return NULL;
}
RANGE_ASSERT(op->ov_rmagic == RMAGIC);
RANGE_ASSERT(*(unsigned short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
i = op->ov_index;
/*
* If the block isn't in a bin, just realloc it.
*/
if (i == 0xff) {
struct block *prevPtr, *nextPtr;
bigBlockPtr = (struct block *) op - 1;
prevPtr = bigBlockPtr->prevPtr;
nextPtr = bigBlockPtr->nextPtr;
bigBlockPtr = (struct block *) TclpSysRealloc(bigBlockPtr,
sizeof(struct block) + OVERHEAD + nbytes);
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;
}
op = (union overhead *) (bigBlockPtr + 1);
#ifdef MSTATS
nmalloc[NBUCKETS]++;
#endif
#ifdef RCHECK
/*
* Record allocated size of block and update magic number bounds.
*/
op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
*(unsigned short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
#endif
Tcl_MutexUnlock(allocMutexPtr);
return (char *)(op+1);
}
maxsize = 1 << (i+3);
expensive = 0;
if ( nbytes + OVERHEAD > maxsize ) {
expensive = 1;
} else if ( i > 0 && nbytes + OVERHEAD < (maxsize/2) ) {
expensive = 1;
}
if (expensive) {
void *newp;
Tcl_MutexUnlock(allocMutexPtr);
newp = TclpAlloc(nbytes);
if ( newp == NULL ) {
return NULL;
}
maxsize -= OVERHEAD;
if ( maxsize < nbytes )
nbytes = maxsize;
memcpy((VOID *) newp, (VOID *) cp, (size_t) nbytes);
TclpFree(cp);
return newp;
}
/*
* Ok, we don't have to copy, it fits as-is
*/
#ifdef RCHECK
op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
*(unsigned short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
#endif
Tcl_MutexUnlock(allocMutexPtr);
return(cp);
}
/*
*----------------------------------------------------------------------
*
* 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(s)
char *s; /* Where to write info. */
{
register int i, j;
register union overhead *p;
int totfree = 0,
totused = 0;
Tcl_MutexLock(allocMutexPtr);
fprintf(stderr, "Memory allocation statistics %s\nTclpFree:\t", s);
for (i = 0; i < NBUCKETS; i++) {
for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
fprintf(stderr, " %d", j);
totfree += j * (1 << (i + 3));
}
fprintf(stderr, "\nused:\t");
for (i = 0; i < NBUCKETS; i++) {
fprintf(stderr, " %d", nmalloc[i]);
totused += nmalloc[i] * (1 << (i + 3));
}
fprintf(stderr, "\n\tTotal small in use: %d, total free: %d\n",
totused, totfree);
fprintf(stderr, "\n\tNumber of big (>%d) blocks in use: %d\n",
MAXMALLOC, nmalloc[NBUCKETS]);
Tcl_MutexUnlock(allocMutexPtr);
}
#endif
#else /* !USE_TCLALLOC */
/*
*----------------------------------------------------------------------
*
* TclpAlloc --
*
* Allocate more memory.
*
* Results:
* None.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
char *
TclpAlloc(nbytes)
unsigned int nbytes; /* Number of bytes to allocate. */
{
return (char*) malloc(nbytes);
}
/*
*----------------------------------------------------------------------
*
* TclpFree --
*
* Free memory.
*
* Results:
* None.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
void
TclpFree(cp)
char *cp; /* Pointer to memory to free. */
{
free(cp);
return;
}
/*
*----------------------------------------------------------------------
*
* TclpRealloc --
*
* Reallocate memory.
*
* Results:
* None.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
char *
TclpRealloc(cp, nbytes)
char *cp; /* Pointer to alloced block. */
unsigned int nbytes; /* New size of memory. */
{
return (char*) realloc(cp, nbytes);
}
#endif /* !USE_TCLALLOC */
#endif /* !TCL_THREADS */