4.3BSD-UWisc/src/sys/sys/heap_kmem.c
/* @(#)heap_kmem.c 1.1 86/02/03 Copyr 1984 Sun Micro */
/* NFSSRC @(#)heap_kmem.c 2.6 86/05/14 */
/* define DEBUG ON */
/*
* Copyright (c) 1984 by Sun Microsystems, Inc.
*/
/*
* Conditions on use:
* kmem_alloc and kmem_free must not be called from interrupt level,
* except from software interrupt level. This is because they are
* not reentrant, and only block out software interrupts. They take
* too long to block any real devices. There is a routine
* kmem_free_intr that can be used to free blocks at interrupt level,
* but only up to splimp, not higher. This is because kmem_free_intr
* only spl's to splimp.
*
* Also, these routines are not that fast, so they should not be used
* in very frequent operations (e.g. operations that happen more often
* than, say, once every few seconds).
*/
/*
* description:
* Yet another memory allocator, this one based on a method
* described in C.J. Stephenson, "Fast Fits", IBM Sys. Journal
*
* The basic data structure is a "Cartesian" binary tree, in which
* nodes are ordered by ascending addresses (thus minimizing free
* list insertion time) and block sizes decrease with depth in the
* tree (thus minimizing search time for a block of a given size).
*
* In other words, for any node s, letting D(s) denote
* the set of descendents of s, we have:
*
* a. addr(D(left(s))) < addr(s) < addr(D(right(s)))
* b. len(D(left(s))) <= len(s) >= len(D(right(s)))
*/
#include "../machine/pte.h"
#include "param.h"
#include "map.h"
#include "time.h"
#include "proc.h"
#include "cmap.h"
#include "kernel.h"
#include "vm.h"
/*
* The node header structure.
*
* To reduce storage consumption, a header block is associated with
* free blocks only, not allocated blocks.
* When a free block is allocated, its header block is put on
* a free header block list.
*
* This creates a header space and a free block space.
* The left pointer of a header blocks is used to chain free header
* blocks together.
*/
typedef enum {false,true} bool;
typedef struct freehdr *Freehdr;
typedef struct dblk *Dblk;
/*
* Description of a header for a free block
* Only free blocks have such headers.
*/
struct freehdr {
Freehdr left; /* Left tree pointer */
Freehdr right; /* Right tree pointer */
Dblk block; /* Ptr to the data block */
u_int size; /* Size of the data block */
};
#define NIL ((Freehdr) 0)
#define WORDSIZE sizeof (int)
#define SMALLEST_BLK 1 /* Size of smallest block */
/*
* Description of a data block.
*/
struct dblk {
char data[1]; /* Addr returned to the caller */
};
/*
* weight(x) is the size of a block, in bytes; or 0 if and only if x
* is a null pointer. It is the responsibility of kmem_alloc() and
* kmem_free() to keep zero-length blocks out of the arena.
*/
#define weight(x) ((x) == NIL? 0: (x->size))
#define nextblk(p, size) ((Dblk) ((char *) (p) + (size)))
#define max(a, b) ((a) < (b)? (b): (a))
Freehdr getfreehdr();
bool morecore();
caddr_t getpages();
caddr_t kmem_alloc();
/*
* Structure containing various info about allocated memory.
*/
#define NEED_TO_FREE_SIZE 10
struct kmem_info {
Freehdr free_root;
Freehdr free_hdr_list;
struct map *map;
struct pte *pte;
caddr_t vaddr;
struct need_to_free {
caddr_t addr;
u_int nbytes;
} need_to_free_list,need_to_free[NEED_TO_FREE_SIZE];
} kmem_info;
/*
* Initialize kernel memory allocator
*/
kmem_init()
{
register int i;
register struct need_to_free *ntf;
#ifdef DEBUG
printf("kmem_init entered\n");
#endif
kmem_info.free_root = NIL;
kmem_info.free_hdr_list = NULL;
kmem_info.map = kernelmap;
kmem_info.pte = Usrptmap;
kmem_info.vaddr = (caddr_t) usrpt;
kmem_info.need_to_free_list.addr = 0;
ntf = kmem_info.need_to_free;
for (i = 0; i < NEED_TO_FREE_SIZE; i++) {
ntf[i].addr = 0;
}
#ifdef DEBUG
printf("kmem_init returning\n");
prtree(kmem_info.free_root, "kmem_init");
#endif
}
/*
* Insert a new node in a cartesian tree or subtree, placing it
* in the correct position with respect to the existing nodes.
*
* algorithm:
* Starting from the root, a binary search is made for the new
* node. If this search were allowed to continue, it would
* eventually fail (since there cannot already be a node at the
* given address); but in fact it stops when it reaches a node in
* the tree which has a length less than that of the new node (or
* when it reaches a null tree pointer). The new node is then
* inserted at the root of the subtree for which the shorter node
* forms the old root (or in place of the null pointer).
*/
insert(p, len, tree)
register Dblk p; /* Ptr to the block to insert */
register u_int len; /* Length of new node */
register Freehdr *tree; /* Address of ptr to root */
{
register Freehdr x;
register Freehdr *left_hook; /* Temp for insertion */
register Freehdr *right_hook; /* Temp for insertion */
register Freehdr newhdr;
x = *tree;
/*
* Search for the first node which has a weight less
* than that of the new node; this will be the
* point at which we insert the new node.
*/
while (weight(x) >= len) {
if (p < x->block)
tree = &x->left;
else
tree = &x->right;
x = *tree;
}
/*
* Perform root insertion. The variable x traces a path through
* the tree, and with the help of left_hook and right_hook,
* rewrites all links that cross the territory occupied
* by p. Note that this improves performance under
* paging.
*/
newhdr = getfreehdr();
*tree = newhdr;
left_hook = &newhdr->left;
right_hook = &newhdr->right;
newhdr->left = NIL;
newhdr->right = NIL;
newhdr->block = p;
newhdr->size = len;
while (x != NIL) {
/*
* Remark:
* The name 'left_hook' is somewhat confusing, since
* it is always set to the address of a .right link
* field. However, its value is always an address
* below (i.e., to the left of) p. Similarly
* for right_hook. The values of left_hook and
* right_hook converge toward the value of p,
* as in a classical binary search.
*/
if (x->block < p) {
/*
* rewrite link crossing from the left
*/
*left_hook = x;
left_hook = &x->right;
x = x->right;
} else {
/*
* rewrite link crossing from the right
*/
*right_hook = x;
right_hook = &x->left;
x = x->left;
} /*else*/
} /*while*/
*left_hook = *right_hook = NIL; /* clear remaining hooks */
} /*insert*/
/*
* Delete a node from a cartesian tree. p is the address of
* a pointer to the node which is to be deleted.
*
* algorithm:
* The left and right sons of the node to be deleted define two
* subtrees which are to be merged and attached in place of the
* deleted node. Each node on the inside edges of these two
* subtrees is examined and longer nodes are placed above the
* shorter ones.
*
* On entry:
* *p is assumed to be non-null.
*/
delete(p)
register Freehdr *p;
{
register Freehdr x;
register Freehdr left_branch; /* left subtree of deleted node */
register Freehdr right_branch; /* right subtree of deleted node */
x = *p;
left_branch = x->left;
right_branch = x->right;
while (left_branch != right_branch) {
/*
* iterate until left branch and right branch are
* both NIL.
*/
if (weight(left_branch) >= weight(right_branch)) {
/*
* promote the left branch
*/
*p = left_branch;
p = &left_branch->right;
left_branch = left_branch->right;
} else {
/*
* promote the right branch
*/
*p = right_branch;
p = &right_branch->left;
right_branch = right_branch->left;
}/*else*/
}/*while*/
*p = NIL;
freehdr(x);
} /*delete*/
/*
* Demote a node in a cartesian tree, if necessary, to establish
* the required vertical ordering.
*
* algorithm:
* The left and right subtrees of the node to be demoted are to
* be partially merged and attached in place of the demoted node.
* The nodes on the inside edges of these two subtrees are
* examined and the longer nodes are placed above the shorter
* ones, until a node is reached which has a length no greater
* than that of the node being demoted (or until a null pointer
* is reached). The node is then attached at this point, and
* the remaining subtrees (if any) become its descendants.
*
* on entry:
* a. All the nodes in the tree, including the one to be demoted,
* must be correctly ordered horizontally;
* b. All the nodes except the one to be demoted must also be
* correctly positioned vertically. The node to be demoted
* may be already correctly positioned vertically, or it may
* have a length which is less than that of one or both of
* its progeny.
* c. *p is non-null
*/
demote(p)
register Freehdr *p;
{
register Freehdr x; /* addr of node to be demoted */
register Freehdr left_branch;
register Freehdr right_branch;
register u_int wx;
x = *p;
left_branch = x->left;
right_branch = x->right;
wx = weight(x);
while (weight(left_branch) > wx || weight(right_branch) > wx) {
/*
* select a descendant branch for promotion
*/
if (weight(left_branch) >= weight(right_branch)) {
/*
* promote the left branch
*/
*p = left_branch;
p = &left_branch->right;
left_branch = *p;
} else {
/*
* promote the right branch
*/
*p = right_branch;
p = &right_branch->left;
right_branch = *p;
} /*else*/
} /*while*/
*p = x; /* attach demoted node here */
x->left = left_branch;
x->right = right_branch;
} /*demote*/
/*
* Allocate a block of storage
*
* algorithm:
* The freelist is searched by descending the tree from the root
* so that at each decision point the "better fitting" child node
* is chosen (i.e., the shorter one, if it is long enough, or
* the longer one, otherwise). The descent stops when both
* child nodes are too short.
*
* function result:
* kmem_alloc returns a pointer to the allocated block; a null
* pointer indicates storage could not be allocated.
*/
/*
* We need to return blocks that are on word boundaries so that callers
* that are putting int's into the area will work. Since we allow
* arbitrary free'ing, we need a weight function that considers
* free blocks starting on an odd boundary special. Allocation is
* aligned to 4 byte boundaries (ALIGN).
*/
#define ALIGN sizeof(int)
#define ALIGNMASK (ALIGN-1)
#define ALIGNMORE(addr) (ALIGN - ((int)(addr) & ALIGNMASK))
#define mweight(x) ((x) == NIL ? 0 : \
((((int)(x)->block) & ALIGNMASK) && ((x)->size > ALIGNMORE((x)->block)))\
? (x)->size - ALIGNMORE((x)->block) : (x)->size)
caddr_t
kmem_alloc(nbytes)
register u_int nbytes;
{
register Freehdr a; /* ptr to node to be allocated */
register Freehdr *p; /* address of ptr to node */
register u_int left_weight;
register u_int right_weight;
register Freehdr left_son;
register Freehdr right_son;
register char *retblock; /* Address returned to the user */
int s;
if (nbytes == 0) {
return(NULL);
}
s = splnet();
if (nbytes < SMALLEST_BLK) {
printf("illegal kmem_alloc call for %d bytes\n", nbytes);
panic("kmem_alloc");
}
check_need_to_free();
/*
* ensure that at least one block is big enough to satisfy
* the request.
*/
if (mweight(kmem_info.free_root) < nbytes) {
/*
* the largest block is not enough.
*/
if (!morecore(nbytes)) {
printf("kmem_alloc failed, nbytes %d\n", nbytes);
panic("kmem_alloc");
}
}
/*
* search down through the tree until a suitable block is
* found. At each decision point, select the better
* fitting node.
*/
p = (Freehdr *) &kmem_info.free_root;
a = *p;
left_son = a->left;
right_son = a->right;
left_weight = mweight(left_son);
right_weight = mweight(right_son);
while (left_weight >= nbytes || right_weight >= nbytes) {
if (left_weight <= right_weight) {
if (left_weight >= nbytes) {
p = &a->left;
a = left_son;
} else {
p = &a->right;
a = right_son;
}
} else {
if (right_weight >= nbytes) {
p = &a->right;
a = right_son;
} else {
p = &a->left;
a = left_son;
}
}
left_son = a->left;
right_son = a->right;
left_weight = mweight(left_son);
right_weight = mweight(right_son);
} /*while*/
/*
* allocate storage from the selected node.
*/
if (a->size - nbytes < SMALLEST_BLK) {
/*
* not big enough to split; must leave at least
* a dblk's worth of space.
*/
retblock = a->block->data;
delete(p);
} else {
/*
* split the node, allocating nbytes from the top.
* Remember we've already accounted for the
* allocated node's header space.
*/
register Freehdr x;
x = getfreehdr();
if ((int) a->block->data & ALIGNMASK &&
a->size > ALIGNMORE(a->block->data)) {
nbytes += ALIGNMORE(a->block->data);
x->block = a->block;
x->size = ALIGNMORE(a->block->data);
x->left = a->left;
x->right = a->right;
/*
* the node pointed to by *p has become smaller;
* move it down to its appropriate place in
* the tree.
*/
*p = x;
demote(p);
/*
rmlog(0, a->block, 1, caller());
rmlog(1, a->block, 1, caller());
*/
retblock = a->block->data + ALIGNMORE(a->block->data);
if (a->size > nbytes) {
/*
rmlog(0, nextblk(a->block, nbytes), a->size - nbytes, caller());
*/
kmem_free((caddr_t)nextblk(a->block, nbytes),
(u_int)a->size - nbytes);
}
freehdr(a);
nbytes -= ALIGNMORE(a->block->data);
} else {
x->block = nextblk(a->block, nbytes);
x->size = a->size - nbytes;
x->left = a->left;
x->right = a->right;
/*
* the node pointed to by *p has become smaller;
* move it down to its appropriate place in
* the tree.
*/
*p = x;
demote(p);
retblock = a->block->data;
freehdr(a);
}
}
#ifdef DEBUG
printf("kmem_alloc returning %x\n", retblock);
prtree(kmem_info.free_root, "kmem_alloc");
#endif
/*
rmlog(0, retblock, nbytes, caller());
*/
splx(s);
return (retblock);
} /*malloc*/
/*
* Return a block to the free space tree.
*
* algorithm:
* Starting at the root, search for and coalesce free blocks
* adjacent to one given. When the appropriate place in the
* tree is found, insert the given block.
*
* Do some sanity checks to avoid total confusion in the tree.
* If the block has already been freed, panic.
* If the ptr is not from the arena, panic.
*/
kmem_free(ptr, nbytes)
caddr_t ptr;
register u_int nbytes; /* Size of node to be released */
{
register Freehdr *np; /* For deletion from free list */
register Freehdr neighbor; /* Node to be coalesced */
register char *neigh_block; /* Ptr to potential neighbor */
register u_int neigh_size; /* Size of potential neighbor */
int s;
#ifdef DEBUG
printf("kmem_free. ptr %x nbytes %d\n", ptr, nbytes);
prtree(kmem_info.free_root, "kmem_free");
#endif
if (nbytes == 0) {
return;
}
/*
* check bounds of pointer.
*/
if (ptr < (caddr_t) usrpt ||
ptr > (caddr_t) usrpt + USRPTSIZE*NBPG) {
printf("kmem_free: illegal pointer %x\n",ptr);
panic("kmem_free");
return;
}
s = splnet();
/*
bzero(ptr, nbytes);
rmlog(1, ptr, nbytes, caller());
*/
/*
* Search the tree for the correct insertion point for this
* node, coalescing adjacent free blocks along the way.
*/
np = &kmem_info.free_root;
neighbor = *np;
while (neighbor != NIL) {
neigh_block = (char *) neighbor->block;
neigh_size = neighbor->size;
if (ptr < neigh_block) {
if (ptr + nbytes == neigh_block) {
/*
* Absorb and delete right neighbor
*/
nbytes += neigh_size;
delete(np);
} else if (ptr + nbytes > neigh_block) {
/*
* The block being freed overlaps
* another block in the tree. This
* is bad news.
*/
printf("kmem_free: free block overlap %x+%d over %x\n", ptr, nbytes, neigh_block);
panic("kmem_free: free block overlap");
} else {
/*
* Search to the left
*/
np = &neighbor->left;
}
} else if (ptr > neigh_block) {
if (neigh_block + neigh_size == ptr) {
/*
* Absorb and delete left neighbor
*/
ptr = neigh_block;
nbytes += neigh_size;
delete(np);
} else if (neigh_block + neigh_size > ptr) {
/*
* This block has already been freed
*/
panic("kmem_free block already free");
} else {
/*
* search to the right
*/
np = &neighbor->right;
}
} else {
/*
* This block has already been freed
* as "ptr == neigh_block"
*/
panic("kmem_free: block already free as neighbor");
return;
} /*else*/
neighbor = *np;
} /*while*/
/*
* Insert the new node into the free space tree
*/
insert((Dblk) ptr, nbytes, &kmem_info.free_root);
#ifdef DEBUG
printf("exiting kmem_free\n");
prtree(kmem_info.free_root, "kmem_free");
#endif
splx(s);
} /*free*/
/*
* We maintain a list of blocks that need to be freed.
* This is because we don't want to spl the relatively long
* routines malloc and free, but we need to be able to free
* space at interrupt level.
*/
kmem_free_intr(ptr, nbytes)
caddr_t ptr;
register u_int nbytes; /* Size of node to be released */
{
register int i;
register struct need_to_free *ntf;
int s;
s = splimp();
if (nbytes >= sizeof (struct need_to_free)) {
if ((int) ptr & ALIGNMASK) {
i = ALIGNMORE(ptr);
kmem_free_intr(ptr, i);
kmem_free_intr(ptr + i, nbytes - i);
return;
}
ntf = &kmem_info.need_to_free_list;
*(struct need_to_free *) ptr = *ntf;
ntf->addr = ptr;
ntf->nbytes = nbytes;
(void) splx(s);
return;
}
ntf = kmem_info.need_to_free;
for (i = 0; i < NEED_TO_FREE_SIZE; i++) {
if (ntf[i].addr == 0) {
ntf[i].addr = ptr;
ntf[i].nbytes = nbytes;
(void) splx(s);
return;
}
}
panic("kmem_free_intr");
}
static
check_need_to_free()
{
register int i;
register struct need_to_free *ntf;
caddr_t addr;
u_int nbytes;
int s;
again:
s = splimp();
ntf = &kmem_info.need_to_free_list;
if (ntf->addr) {
addr = ntf->addr;
nbytes = ntf->nbytes;
*ntf = *(struct need_to_free *) ntf->addr;
(void) splx(s);
kmem_free(addr, nbytes);
goto again;
}
ntf = kmem_info.need_to_free;
for (i = 0; i < NEED_TO_FREE_SIZE; i++) {
if (ntf[i].addr) {
addr = ntf[i].addr;
nbytes = ntf[i].nbytes;
ntf[i].addr = 0;
(void) splx(s);
kmem_free(addr, nbytes);
goto again;
}
}
(void) splx(s);
}
/*
* Add a block of at least nbytes to the free space tree.
*
* return value:
* true if at least nbytes can be allocated
* false otherwise
*
* remark:
* free space (delimited by the static variable ubound) is
* extended by an amount determined by rounding nbytes up to
* a multiple of the system page size.
*/
bool
morecore(nbytes)
u_int nbytes;
{
Dblk p;
nbytes = roundup(nbytes, CLBYTES);
p = (Dblk) getpages(nbytes / NBPG);
if (p == 0) {
return (false);
}
kmem_free((caddr_t) p, nbytes);
return (true);
} /*morecore*/
/*
* get npages pages from the system
*/
caddr_t
getpages(npages)
u_int npages;
{
register caddr_t va;
register long x;
int s;
extern char kmapwnt;
s = splimp();
while ((x = rmalloc(kmem_info.map, (long)npages)) == 0) {
kmapwnt = 1; /* XXX */
#ifdef sun
if (intsvc()) {
panic("getpages called at interrupt level");
}
#endif sun
sleep((caddr_t)kmem_info.map, PZERO - 1);
}
(void) vmemall(&(kmem_info.pte)[x], (int)npages, &proc[0], CSYS);
va = kmem_info.vaddr + (x << PGSHIFT);
vmaccess(&(kmem_info.pte)[x], va, (int)npages);
#ifdef DEBUG
printf("getpages returning 0x%x, %d pages, x was %d\n", va, npages, x);
#endif
(void) splx(s);
return (va);
}
/*
* Get a free block header
* There is a list of available free block headers.
* When the list is empty, allocate another pagefull.
*/
Freehdr
getfreehdr()
{
Freehdr r;
int n;
if (kmem_info.free_hdr_list != NIL) {
r = kmem_info.free_hdr_list;
kmem_info.free_hdr_list = kmem_info.free_hdr_list->left;
} else {
r = (Freehdr) getpages(CLSIZE);
if (r == 0) {
panic("getfreehdr");
}
for (n = 1; n < CLBYTES / sizeof (*r); n++) {
freehdr(&r[n]);
}
}
return (r);
}
/*
* Free a free block header
* Add it to the list of available headers.
*/
freehdr(p)
Freehdr p;
{
p->left = kmem_info.free_hdr_list;
p->right = NIL;
p->block = NULL;
kmem_info.free_hdr_list = p;
}
#ifdef DEBUG
/*
* Diagnostic routines
*/
static depth = 0;
prtree(p, cp)
Freehdr p;
char *cp;
{
int n;
if (depth == 0) {
printf("prtree. p %x cp %s\n", p, cp);
/*
} else {
printf("prtree. p %x depth %d\n", p, depth);
*/
}
if (p != NIL){
depth++;
prtree(p->left, (char *)NULL);
depth--;
for (n = 0; n < depth; n++) {
printf(" ");
}
printf(
"(%x): (left = %x, right = %x, block = %x, size = %d)\n",
p, p->left, p->right, p->block, p->size);
depth++;
prtree(p->right, (char *)NULL);
depth--;
}
}
#endif