-/* @(#)malloc.c 4.1 (Berkeley) 12/21/80 */
+#ifndef lint
+static char sccsid[] = "@(#)malloc.c 4.3 (Berkeley) 9/16/83";
+#endif
+
+/*
+ * malloc.c (Caltech) 2/21/82
+ * Chris Kingsley, kingsley@cit-20.
+ *
+ * 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. In this
+ * implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long.
+ * This is designed for use in a program that uses vast quantities of memory,
+ * but bombs when it runs out.
+ */
+
+#include <sys/types.h>
+
+#define NULL 0
+
+/*
+ * The overhead on a block is at least 4 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 and the size of the block fits
+ * in two bytes, then the top two bytes hold the size of the requested block
+ * plus the range checking words, and the header word MINUS ONE.
+ */
+union overhead {
+ union overhead *ov_next; /* when free */
+ struct {
+ u_char ovu_magic; /* magic number */
+ u_char ovu_index; /* bucket # */
+#ifdef RCHECK
+ u_short ovu_size; /* actual block size */
+ u_int ovu_rmagic; /* range magic number */
+#endif
+ } ovu;
+#define ov_magic ovu.ovu_magic
+#define ov_index ovu.ovu_index
+#define ov_size ovu.ovu_size
+#define ov_rmagic ovu.ovu_rmagic
+};
+
+#define MAGIC 0xff /* magic # on accounting info */
+#define RMAGIC 0x55555555 /* magic # on range info */
+#ifdef RCHECK
+#define RSLOP sizeof (u_int)
+#else
+#define RSLOP 0
+#endif
+
+/*
+ * 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 30
+static union overhead *nextf[NBUCKETS];
+extern char *sbrk();
+
+#ifdef MSTATS
+/*
+ * nmalloc[i] is the difference between the number of mallocs and frees
+ * for a given block size.
+ */
+static u_int nmalloc[NBUCKETS];
+#include <stdio.h>
+#endif
+
#ifdef debug
-#define ASSERT(p) if(!(p))botch("p");else
+#define ASSERT(p) if (!(p)) botch("p"); else
+static
botch(s)
-char *s;
+ char *s;
{
- printf("assertion botched: %s\n",s);
+
+ printf("assertion botched: %s\n", s);
abort();
}
#else
-#define ASSERT(p)
+#define ASSERT(p)
#endif
-/* avoid break bug */
-#ifdef pdp11
-#define GRANULE 64
-#else
-#define GRANULE 0
-#endif
-/* C storage allocator
- * circular first-fit strategy
- * works with noncontiguous, but monotonically linked, arena
- * each block is preceded by a ptr to the (pointer of)
- * the next following block
- * blocks are exact number of words long
- * aligned to the data type requirements of ALIGN
- * pointers to blocks must have BUSY bit 0
- * bit in ptr is 1 for busy, 0 for idle
- * gaps in arena are merely noted as busy blocks
- * last block of arena (pointed to by alloct) is empty and
- * has a pointer to first
- * idle blocks are coalesced during space search
- *
- * a different implementation may need to redefine
- * ALIGN, NALIGN, BLOCK, BUSY, INT
- * where INT is integer type to which a pointer can be cast
-*/
-#define INT int
-#define ALIGN int
-#define NALIGN 1
-#define WORD sizeof(union store)
-#define BLOCK 1024 /* a multiple of WORD*/
-#define BUSY 1
-#define NULL 0
-#define testbusy(p) ((INT)(p)&BUSY)
-#define setbusy(p) (union store *)((INT)(p)|BUSY)
-#define clearbusy(p) (union store *)((INT)(p)&~BUSY)
-
-union store { union store *ptr;
- ALIGN dummy[NALIGN];
- int calloc; /*calloc clears an array of integers*/
-};
-
-static union store allocs[2]; /*initial arena*/
-static union store *allocp; /*search ptr*/
-static union store *alloct; /*arena top*/
-static union store *allocx; /*for benefit of realloc*/
-char *sbrk();
-
char *
malloc(nbytes)
-unsigned nbytes;
+ register unsigned nbytes;
{
- register union store *p, *q;
- register nw;
- static temp; /*coroutines assume no auto*/
-
- if(allocs[0].ptr==0) { /*first time*/
- allocs[0].ptr = setbusy(&allocs[1]);
- allocs[1].ptr = setbusy(&allocs[0]);
- alloct = &allocs[1];
- allocp = &allocs[0];
- }
- nw = (nbytes+WORD+WORD-1)/WORD;
- ASSERT(allocp>=allocs && allocp<=alloct);
- ASSERT(allock());
- for(p=allocp; ; ) {
- for(temp=0; ; ) {
- if(!testbusy(p->ptr)) {
- while(!testbusy((q=p->ptr)->ptr)) {
- ASSERT(q>p&&q<alloct);
- p->ptr = q->ptr;
- }
- if(q>=p+nw && p+nw>=p)
- goto found;
- }
- q = p;
- p = clearbusy(p->ptr);
- if(p>q)
- ASSERT(p<=alloct);
- else if(q!=alloct || p!=allocs) {
- ASSERT(q==alloct&&p==allocs);
- return(NULL);
- } else if(++temp>1)
- break;
- }
- temp = ((nw+BLOCK/WORD)/(BLOCK/WORD))*(BLOCK/WORD);
- q = (union store *)sbrk(0);
- if(q+temp+GRANULE < q) {
- return(NULL);
- }
- q = (union store *)sbrk(temp*WORD);
- if((INT)q == -1) {
- return(NULL);
- }
- ASSERT(q>alloct);
- alloct->ptr = q;
- if(q!=alloct+1)
- alloct->ptr = setbusy(alloct->ptr);
- alloct = q->ptr = q+temp-1;
- alloct->ptr = setbusy(allocs);
- }
-found:
- allocp = p + nw;
- ASSERT(allocp<=alloct);
- if(q>allocp) {
- allocx = allocp->ptr;
- allocp->ptr = p->ptr;
- }
- p->ptr = setbusy(allocp);
- return((char *)(p+1));
+ register union overhead *p;
+ register int bucket = 0;
+ register unsigned shiftr;
+
+ /*
+ * Convert amount of memory requested into
+ * closest block size stored in hash buckets
+ * which satisfies request. Account for
+ * space used per block for accounting.
+ */
+ nbytes += sizeof (union overhead) + RSLOP;
+ nbytes = (nbytes + 3) &~ 3;
+ shiftr = (nbytes - 1) >> 2;
+ /* apart from this loop, this is O(1) */
+ while (shiftr >>= 1)
+ bucket++;
+ /*
+ * If nothing in hash bucket right now,
+ * request more memory from the system.
+ */
+ if (nextf[bucket] == NULL)
+ morecore(bucket);
+ if ((p = (union overhead *)nextf[bucket]) == NULL)
+ return (NULL);
+ /* remove from linked list */
+ nextf[bucket] = nextf[bucket]->ov_next;
+ p->ov_magic = MAGIC;
+ p->ov_index= bucket;
+#ifdef MSTATS
+ nmalloc[bucket]++;
+#endif
+#ifdef RCHECK
+ /*
+ * Record allocated size of block and
+ * bound space with magic numbers.
+ */
+ if (nbytes <= 0x10000)
+ p->ov_size = nbytes - 1;
+ p->ov_rmagic = RMAGIC;
+ *((u_int *)((caddr_t)p + nbytes - RSLOP)) = RMAGIC;
+#endif
+ return ((char *)(p + 1));
}
-/* freeing strategy tuned for LIFO allocation
-*/
-free(ap)
-register char *ap;
+/*
+ * Allocate more memory to the indicated bucket.
+ */
+static
+morecore(bucket)
+ register bucket;
{
- register union store *p = (union store *)ap;
-
- ASSERT(p>clearbusy(allocs[1].ptr)&&p<=alloct);
- ASSERT(allock());
- allocp = --p;
- ASSERT(testbusy(p->ptr));
- p->ptr = clearbusy(p->ptr);
- ASSERT(p->ptr > allocp && p->ptr <= alloct);
+ register union overhead *op;
+ register int rnu; /* 2^rnu bytes will be requested */
+ register int nblks; /* become nblks blocks of the desired size */
+ register int siz;
+
+ if (nextf[bucket])
+ return;
+ /*
+ * Insure memory is allocated
+ * on a page boundary. Should
+ * make getpageize call?
+ */
+ op = (union overhead *)sbrk(0);
+ if ((int)op & 0x3ff)
+ sbrk(1024 - ((int)op & 0x3ff));
+ /* take 2k unless the block is bigger than that */
+ rnu = (bucket <= 8) ? 11 : bucket + 3;
+ nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */
+ if (rnu < bucket)
+ rnu = bucket;
+ op = (union overhead *)sbrk(1 << rnu);
+ /* no more room! */
+ if ((int)op == -1)
+ return;
+ /*
+ * Round up to minimum allocation size boundary
+ * and deduct from block count to reflect.
+ */
+ if ((int)op & 7) {
+ op = (union overhead *)(((int)op + 8) &~ 7);
+ nblks--;
+ }
+ /*
+ * Add new memory allocated to that on
+ * free list for this hash bucket.
+ */
+ nextf[bucket] = op;
+ siz = 1 << (bucket + 3);
+ while (--nblks > 0) {
+ op->ov_next = (union overhead *)((caddr_t)op + siz);
+ op = (union overhead *)((caddr_t)op + siz);
+ }
+}
+
+free(cp)
+ char *cp;
+{
+ register int size;
+ register union overhead *op;
+
+ if (cp == NULL)
+ return;
+ op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
+#ifdef debug
+ ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
+#else
+ if (op->ov_magic != MAGIC)
+ return; /* sanity */
+#endif
+#ifdef RCHECK
+ ASSERT(op->ov_rmagic == RMAGIC);
+ if (op->ov_index <= 13)
+ ASSERT(*(u_int *)((caddr_t)op + op->ov_size + 1 - RSLOP) == RMAGIC);
+#endif
+ ASSERT(op->ov_index < NBUCKETS);
+ size = op->ov_index;
+ op->ov_next = nextf[size];
+ nextf[size] = op;
+#ifdef MSTATS
+ nmalloc[size]--;
+#endif
}
-/* realloc(p, nbytes) reallocates a block obtained from malloc()
- * and freed since last call of malloc()
- * to have new size nbytes, and old content
- * returns new location, or 0 on failure
-*/
+/*
+ * When a program attempts "storage compaction" as mentioned in the
+ * old malloc man page, it realloc's an already freed block. Usually
+ * this is the last block it freed; occasionally it might be farther
+ * back. We have to search all the free lists for the block in order
+ * to determine its bucket: 1st we make one pass thru the lists
+ * checking only the first block in each; if that fails we search
+ * ``realloc_srchlen'' blocks in each list for a match (the variable
+ * is extern so the caller can modify it). If that fails we just copy
+ * however many bytes was given to realloc() and hope it's not huge.
+ */
+int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
char *
-realloc(p, nbytes)
-register union store *p;
-unsigned nbytes;
-{
- register union store *q;
- union store *s, *t;
- register unsigned nw;
- unsigned onw;
-
- if(testbusy(p[-1].ptr))
- free((char *)p);
- onw = p[-1].ptr - p;
- q = (union store *)malloc(nbytes);
- if(q==NULL || q==p)
- return((char *)q);
- s = p;
- t = q;
- nw = (nbytes+WORD-1)/WORD;
- if(nw<onw)
- onw = nw;
- while(onw--!=0)
- *t++ = *s++;
- if(q<p && q+nw>=p)
- (q+(q+nw-p))->ptr = allocx;
- return((char *)q);
+realloc(cp, nbytes)
+ char *cp;
+ unsigned nbytes;
+{
+ register u_int onb;
+ union overhead *op;
+ char *res;
+ register int i;
+ int was_alloced = 0;
+
+ if (cp == NULL)
+ return (malloc(nbytes));
+ op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
+ if (op->ov_magic == MAGIC) {
+ was_alloced++;
+ i = op->ov_index;
+ } else {
+ /*
+ * Already free, doing "compaction".
+ *
+ * Search for the old block of memory on the
+ * free list. First, check the most common
+ * case (last element free'd), then (this failing)
+ * the last ``realloc_srchlen'' items free'd.
+ * If all lookups fail, then assume the size of
+ * the memory block being realloc'd is the
+ * smallest possible.
+ */
+ if ((i = findbucket(op, 1)) < 0 &&
+ (i = findbucket(op, realloc_srchlen)) < 0)
+ i = 0;
+ }
+ onb = (1 << (i + 3)) - sizeof (*op) - RSLOP;
+ /* avoid the copy if same size block */
+ if (was_alloced &&
+ nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP)
+ return(cp);
+ if ((res = malloc(nbytes)) == NULL)
+ return (NULL);
+ if (cp != res) /* common optimization */
+ bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
+ if (was_alloced)
+ free(cp);
+ return (res);
}
-#ifdef debug
-allock()
+/*
+ * Search ``srchlen'' elements of each free list for a block whose
+ * header starts at ``freep''. If srchlen is -1 search the whole list.
+ * Return bucket number, or -1 if not found.
+ */
+static
+findbucket(freep, srchlen)
+ union overhead *freep;
+ int srchlen;
{
-#ifdef longdebug
- register union store *p;
- int x;
- x = 0;
- for(p= &allocs[0]; clearbusy(p->ptr) > p; p=clearbusy(p->ptr)) {
- if(p==allocp)
- x++;
+ register union overhead *p;
+ register int i, j;
+
+ for (i = 0; i < NBUCKETS; i++) {
+ j = 0;
+ for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
+ if (p == freep)
+ return (i);
+ j++;
+ }
}
- ASSERT(p==alloct);
- return(x==1|p==allocp);
-#else
- return(1);
-#endif
+ return (-1);
+}
+
+#ifdef MSTATS
+/*
+ * mstats - print out statistics about malloc
+ *
+ * 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.
+ */
+mstats(s)
+ char *s;
+{
+ register int i, j;
+ register union overhead *p;
+ int totfree = 0,
+ totused = 0;
+
+ fprintf(stderr, "Memory allocation statistics %s\nfree:\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 in use: %d, total free: %d\n",
+ totused, totfree);
}
#endif