457 lines
10 KiB
C
457 lines
10 KiB
C
/*
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* tclAlloc.c --
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*
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* This is a very fast storage allocator. It allocates blocks of a
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* small number of different sizes, and keeps free lists of each size.
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* Blocks that don't exactly fit are passed up to the next larger size.
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* Blocks over a certain size are directly allocated from the system.
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*
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* Copyright (c) 1983 Regents of the University of California.
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* Copyright (c) 1996-1997 Sun Microsystems, Inc.
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*
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* Portions contributed by Chris Kingsley, Jack Jansen and Ray Johnson.
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*
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* See the file "license.terms" for information on usage and redistribution
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* of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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*
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* SCCS: @(#) tclAlloc.c 1.4 97/08/11 18:45:38
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*/
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#include "tclInt.h"
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#include "tclPort.h"
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#ifdef TCL_DEBUG
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# define DEBUG
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/* #define MSTATS */
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# define RCHECK
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#endif
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typedef unsigned long caddr_t;
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/*
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* The overhead on a block is at least 4 bytes. When free, this space
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* contains a pointer to the next free block, and the bottom two bits must
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* be zero. When in use, the first byte is set to MAGIC, and the second
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* byte is the size index. The remaining bytes are for alignment.
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* If range checking is enabled then a second word holds the size of the
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* requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
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* The order of elements is critical: ov_magic must overlay the low order
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* bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
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*/
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union overhead {
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union overhead *ov_next; /* when free */
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struct {
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unsigned char ovu_magic0; /* magic number */
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unsigned char ovu_index; /* bucket # */
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unsigned char ovu_unused; /* unused */
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unsigned char ovu_magic1; /* other magic number */
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#ifdef RCHECK
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unsigned short ovu_rmagic; /* range magic number */
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unsigned long ovu_size; /* actual block size */
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#endif
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} ovu;
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#define ov_magic0 ovu.ovu_magic0
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#define ov_magic1 ovu.ovu_magic1
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#define ov_index ovu.ovu_index
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#define ov_rmagic ovu.ovu_rmagic
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#define ov_size ovu.ovu_size
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};
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#define MAGIC 0xef /* magic # on accounting info */
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#define RMAGIC 0x5555 /* magic # on range info */
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#ifdef RCHECK
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#define RSLOP sizeof (unsigned short)
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#else
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#define RSLOP 0
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#endif
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#define OVERHEAD (sizeof(union overhead) + RSLOP)
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/*
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* nextf[i] is the pointer to the next free block of size 2^(i+3). The
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* smallest allocatable block is 8 bytes. The overhead information
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* precedes the data area returned to the user.
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*/
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#define NBUCKETS 13
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#define MAXMALLOC (1<<(NBUCKETS+2))
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static union overhead *nextf[NBUCKETS];
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#ifdef MSTATS
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/*
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* nmalloc[i] is the difference between the number of mallocs and frees
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* for a given block size.
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*/
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static unsigned int nmalloc[NBUCKETS+1];
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#include <stdio.h>
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#endif
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#if defined(DEBUG) || defined(RCHECK)
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#define ASSERT(p) if (!(p)) panic(# p)
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#define RANGE_ASSERT(p) if (!(p)) panic(# p)
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#else
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#define ASSERT(p)
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#define RANGE_ASSERT(p)
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#endif
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/*
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* Prototypes for functions used only in this file.
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*/
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static void MoreCore _ANSI_ARGS_((int bucket));
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/*
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*----------------------------------------------------------------------
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*
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* TclpAlloc --
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*
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* Allocate more memory.
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*
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* Results:
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* None.
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*
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* Side effects:
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* None.
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*
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*----------------------------------------------------------------------
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*/
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char *
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TclpAlloc(
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unsigned int nbytes) /* Number of bytes to allocate. */
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{
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register union overhead *op;
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register long bucket;
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register unsigned amt;
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/*
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* First the simple case: we simple allocate big blocks directly
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*/
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if (nbytes + OVERHEAD >= MAXMALLOC) {
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op = (union overhead *)TclpSysAlloc(nbytes+OVERHEAD, 0);
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if (op == NULL) {
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return NULL;
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}
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op->ov_magic0 = op->ov_magic1 = MAGIC;
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op->ov_index = 0xff;
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#ifdef MSTATS
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nmalloc[NBUCKETS]++;
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#endif
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#ifdef RCHECK
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/*
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* Record allocated size of block and
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* bound space with magic numbers.
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*/
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op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
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op->ov_rmagic = RMAGIC;
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*(unsigned short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
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#endif
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return (void *)(op+1);
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}
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/*
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* Convert amount of memory requested into closest block size
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* stored in hash buckets which satisfies request.
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* Account for space used per block for accounting.
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*/
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#ifndef RCHECK
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amt = 8; /* size of first bucket */
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bucket = 0;
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#else
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amt = 16; /* size of first bucket */
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bucket = 1;
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#endif
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while (nbytes + OVERHEAD > amt) {
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amt <<= 1;
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if (amt == 0) {
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return (NULL);
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}
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bucket++;
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}
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ASSERT( bucket < NBUCKETS );
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/*
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* If nothing in hash bucket right now,
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* request more memory from the system.
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*/
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if ((op = nextf[bucket]) == NULL) {
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MoreCore(bucket);
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if ((op = nextf[bucket]) == NULL) {
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return (NULL);
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}
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}
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/*
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* Remove from linked list
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*/
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nextf[bucket] = op->ov_next;
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op->ov_magic0 = op->ov_magic1 = MAGIC;
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op->ov_index = (unsigned char) bucket;
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#ifdef MSTATS
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nmalloc[bucket]++;
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#endif
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#ifdef RCHECK
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/*
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* Record allocated size of block and
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* bound space with magic numbers.
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*/
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op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
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op->ov_rmagic = RMAGIC;
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*(unsigned short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
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#endif
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return ((char *)(op + 1));
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}
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/*
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*----------------------------------------------------------------------
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*
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* MoreCore --
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*
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* Allocate more memory to the indicated bucket.
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*
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* Results:
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* None.
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*
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* Side effects:
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* Attempts to get more memory from the system.
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*
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*----------------------------------------------------------------------
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*/
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static void
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MoreCore(
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int bucket) /* What bucket to allocat to. */
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{
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register union overhead *op;
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register long sz; /* size of desired block */
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long amt; /* amount to allocate */
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int nblks; /* how many blocks we get */
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/*
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* sbrk_size <= 0 only for big, FLUFFY, requests (about
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* 2^30 bytes on a VAX, I think) or for a negative arg.
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*/
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sz = 1 << (bucket + 3);
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ASSERT(sz > 0);
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amt = MAXMALLOC;
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nblks = amt / sz;
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ASSERT(nblks*sz == amt);
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op = (union overhead *)TclpSysAlloc(amt, 1);
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/* no more room! */
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if (op == NULL) {
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return;
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}
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/*
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* Add new memory allocated to that on
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* free list for this hash bucket.
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*/
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nextf[bucket] = op;
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while (--nblks > 0) {
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op->ov_next = (union overhead *)((caddr_t)op + sz);
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op = (union overhead *)((caddr_t)op + sz);
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}
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op->ov_next = (union overhead *)NULL;
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}
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/*
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*----------------------------------------------------------------------
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*
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* TclpFree --
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*
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* Free memory.
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*
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* Results:
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* None.
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*
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* Side effects:
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* None.
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*
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*----------------------------------------------------------------------
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*/
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void
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TclpFree(
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char *cp) /* Pointer to memory to free. */
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{
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register long size;
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register union overhead *op;
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if (cp == NULL) {
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return;
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}
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op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
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ASSERT(op->ov_magic0 == MAGIC); /* make sure it was in use */
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ASSERT(op->ov_magic1 == MAGIC);
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if (op->ov_magic0 != MAGIC || op->ov_magic1 != MAGIC) {
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return;
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}
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RANGE_ASSERT(op->ov_rmagic == RMAGIC);
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RANGE_ASSERT(*(unsigned short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
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size = op->ov_index;
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if ( size == 0xff ) {
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#ifdef MSTATS
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nmalloc[NBUCKETS]--;
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#endif
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TclpSysFree(op);
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return;
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}
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ASSERT(size < NBUCKETS);
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op->ov_next = nextf[size]; /* also clobbers ov_magic */
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nextf[size] = op;
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#ifdef MSTATS
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nmalloc[size]--;
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#endif
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}
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/*
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*----------------------------------------------------------------------
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*
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* TclpRealloc --
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*
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* Reallocate memory.
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*
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* Results:
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* None.
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*
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* Side effects:
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* None.
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*
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*----------------------------------------------------------------------
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*/
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char *
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TclpRealloc(
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char *cp, /* Pointer to alloced block. */
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unsigned int nbytes) /* New size of memory. */
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{
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int i;
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union overhead *op;
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int expensive;
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unsigned long maxsize;
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if (cp == NULL) {
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return (TclpAlloc(nbytes));
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}
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op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
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ASSERT(op->ov_magic0 == MAGIC); /* make sure it was in use */
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ASSERT(op->ov_magic1 == MAGIC);
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if (op->ov_magic0 != MAGIC || op->ov_magic1 != MAGIC) {
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return NULL;
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}
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RANGE_ASSERT(op->ov_rmagic == RMAGIC);
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RANGE_ASSERT(*(unsigned short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
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i = op->ov_index;
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/*
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* If the block isn't in a bin, just realloc it.
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*/
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if (i == 0xff) {
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op = (union overhead *) TclpSysRealloc(op, nbytes+OVERHEAD);
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if (op == NULL) {
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return NULL;
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}
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#ifdef MSTATS
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nmalloc[NBUCKETS]++;
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#endif
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#ifdef RCHECK
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/*
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* Record allocated size of block and update magic number bounds.
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*/
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op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
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*(unsigned short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
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#endif
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return (char *)(op+1);
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}
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maxsize = 1 << (i+3);
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expensive = 0;
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if ( nbytes + OVERHEAD > maxsize ) {
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expensive = 1;
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} else if ( i > 0 && nbytes + OVERHEAD < (maxsize/2) ) {
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expensive = 1;
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}
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if (expensive) {
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void *newp;
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newp = TclpAlloc(nbytes);
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if ( newp == NULL ) {
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return NULL;
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}
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maxsize -= OVERHEAD;
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if ( maxsize < nbytes )
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nbytes = maxsize;
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memcpy((VOID *) newp, (VOID *) cp, (size_t) nbytes);
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TclpFree(cp);
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return newp;
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}
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/*
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* Ok, we don't have to copy, it fits as-is
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*/
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#ifdef RCHECK
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op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
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*(unsigned short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
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#endif
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return(cp);
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}
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/*
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*----------------------------------------------------------------------
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*
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* mstats --
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*
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* Prints two lines of numbers, one showing the length of the
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* free list for each size category, the second showing the
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* number of mallocs - frees for each size category.
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*
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* Results:
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* None.
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*
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* Side effects:
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* None.
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*
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*----------------------------------------------------------------------
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*/
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#ifdef MSTATS
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void
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mstats(
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char *s) /* Where to write info. */
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{
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register int i, j;
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register union overhead *p;
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int totfree = 0,
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totused = 0;
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fprintf(stderr, "Memory allocation statistics %s\nTclpFree:\t", s);
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for (i = 0; i < NBUCKETS; i++) {
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for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
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fprintf(stderr, " %d", j);
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totfree += j * (1 << (i + 3));
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}
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fprintf(stderr, "\nused:\t");
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for (i = 0; i < NBUCKETS; i++) {
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fprintf(stderr, " %d", nmalloc[i]);
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totused += nmalloc[i] * (1 << (i + 3));
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}
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fprintf(stderr, "\n\tTotal small in use: %d, total free: %d\n",
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totused, totfree);
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fprintf(stderr, "\n\tNumber of big (>%d) blocks in use: %d\n",
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MAXMALLOC, nmalloc[NBUCKETS]);
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}
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#endif
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