sanchayanmaity/minix
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

VM: forget about 'holes'

Browse source 
. unused data structures and code
This commit is contained in:
Ben Gras 2012-09-18 13:17:46 +02:00
parent 6410f4b5db
commit 8821c73a9e
1 changed files with 1 additions and 218 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

219
servers/vm/alloc.c
View file

@ -1,17 +1,5 @@
/* This file is concerned with allocating and freeing arbitrary-size blocks of
* physical memory on behalf of the FORK and EXEC system calls. The key data
* structure used is the hole table, which maintains a list of holes in memory.
* It is kept sorted in order of increasing memory address. The addresses
* it contains refers to physical memory, starting at absolute address 0
* (i.e., they are not relative to the start of PM). During system
* initialization, that part of memory containing the interrupt vectors,
* kernel, and PM are "allocated" to mark them as not available and to
* remove them from the hole list.
*
* The entry points into this file are:
* alloc_mem: allocate a given sized chunk of memory
* free_mem: release a previously allocated chunk of memory
* mem_init: initialize the tables when PM start up
* physical memory.
*/
#define _SYSTEM 1
@ -49,110 +37,14 @@ addr_avl addravl;
/* Used for sanity check. */
static phys_bytes mem_low, mem_high;
struct hole {
struct hole *h_next; /* pointer to next entry on the list */
phys_clicks h_base; /* where does the hole begin? */
phys_clicks h_len; /* how big is the hole? */
int freelist;
int holelist;
};
#define _NR_HOLES (_NR_PROCS*2) /* No. of memory holes maintained by VM */
static struct hole hole[_NR_HOLES];
static struct hole *hole_head; /* pointer to first hole */
static struct hole *free_slots;/* ptr to list of unused table slots */
static void del_slot(struct hole *prev_ptr, struct hole *hp);
static void merge(struct hole *hp);
static void free_pages(phys_bytes addr, int pages);
static phys_bytes alloc_pages(int pages, int flags, phys_bytes *ret);
#if SANITYCHECKS
static void holes_sanity_f(char *fn, int line);
#define CHECKHOLES holes_sanity_f(__FILE__, __LINE__)
#define PAGESPERGB (1024*1024*1024/VM_PAGE_SIZE) /* 1GB of memory */
#define MAXPAGES (2*PAGESPERGB)
#define CHUNKS BITMAP_CHUNKS(MAXPAGES)
static bitchunk_t pagemap[CHUNKS];
#else
#define CHECKHOLES
#endif
#if SANITYCHECKS
/*===========================================================================*
* holes_sanity_f *
*===========================================================================*/
static void holes_sanity_f(file, line)
char *file;
int line;
{
#define myassert(c) { \
if(!(c)) { \
printf("holes_sanity_f:%s:%d: %s failed\n", file, line, #c); \
util_stacktrace(); \
panic("assert failed"); } \
}
int h, c = 0, n = 0;
struct hole *hp;
/* Reset flags */
for(h = 0; h < _NR_HOLES; h++) {
hole[h].freelist = 0;
hole[h].holelist = 0;
}
/* Mark all holes on freelist. */
for(hp = free_slots; hp; hp = hp->h_next) {
myassert(!hp->freelist);
myassert(!hp->holelist);
hp->freelist = 1;
myassert(c < _NR_HOLES);
c++;
n++;
}
/* Mark all holes on holelist. */
c = 0;
for(hp = hole_head; hp; hp = hp->h_next) {
myassert(!hp->freelist);
myassert(!hp->holelist);
hp->holelist = 1;
myassert(c < _NR_HOLES);
c++;
n++;
}
/* Check there are exactly the right number of nodes. */
myassert(n == _NR_HOLES);
/* Make sure each slot is on exactly one of the list. */
c = 0;
for(h = 0; h < _NR_HOLES; h++) {
hp = &hole[h];
myassert(hp->holelist || hp->freelist);
myassert(!(hp->holelist && hp->freelist));
myassert(c < _NR_HOLES);
c++;
}
/* Make sure no holes overlap. */
for(hp = hole_head; hp && hp->h_next; hp = hp->h_next) {
myassert(hp->holelist);
hp->holelist = 1;
/* No holes overlap. */
myassert(hp->h_base + hp->h_len <= hp->h_next->h_base);
/* No uncoalesced holes. */
myassert(hp->h_base + hp->h_len < hp->h_next->h_base);
}
}
#endif
/*===========================================================================*
@ -185,8 +77,6 @@ phys_clicks alloc_mem(phys_clicks clicks, u32_t memflags)
if(mem == NO_MEM)
return mem;
CHECKHOLES;
if(align_clicks) {
phys_clicks o;
o = mem % align_clicks;
@ -197,7 +87,6 @@ CHECKHOLES;
mem += e;
}
}
CHECKHOLES;
return mem;
}
@ -212,105 +101,11 @@ void free_mem(phys_clicks base, phys_clicks clicks)
* to the hole list. If it is contiguous with an existing hole on either end,
* it is merged with the hole or holes.
*/
register struct hole *hp, *new_ptr, *prev_ptr;
CHECKHOLES;
if (clicks == 0) return;
assert(CLICK_SIZE == VM_PAGE_SIZE);
free_pages(base, clicks);
return;
if ( (new_ptr = free_slots) == NULL)
panic("hole table full");
new_ptr->h_base = base;
new_ptr->h_len = clicks;
free_slots = new_ptr->h_next;
hp = hole_head;
/* If this block's address is numerically less than the lowest hole currently
* available, or if no holes are currently available, put this hole on the
* front of the hole list.
*/
if (hp == NULL || base <= hp->h_base) {
/* Block to be freed goes on front of the hole list. */
new_ptr->h_next = hp;
hole_head = new_ptr;
merge(new_ptr);
CHECKHOLES;
return;
}
/* Block to be returned does not go on front of hole list. */
prev_ptr = NULL;
while (hp != NULL && base > hp->h_base) {
prev_ptr = hp;
hp = hp->h_next;
}
/* We found where it goes. Insert block after 'prev_ptr'. */
new_ptr->h_next = prev_ptr->h_next;
prev_ptr->h_next = new_ptr;
merge(prev_ptr); /* sequence is 'prev_ptr', 'new_ptr', 'hp' */
CHECKHOLES;
}
/*===========================================================================*
* del_slot *
*===========================================================================*/
static void del_slot(prev_ptr, hp)
/* pointer to hole entry just ahead of 'hp' */
register struct hole *prev_ptr;
/* pointer to hole entry to be removed */
register struct hole *hp;
{
/* Remove an entry from the hole list. This procedure is called when a
* request to allocate memory removes a hole in its entirety, thus reducing
* the numbers of holes in memory, and requiring the elimination of one
* entry in the hole list.
*/
if (hp == hole_head)
hole_head = hp->h_next;
else
prev_ptr->h_next = hp->h_next;
hp->h_next = free_slots;
hp->h_base = hp->h_len = 0;
free_slots = hp;
}
/*===========================================================================*
* merge *
*===========================================================================*/
static void merge(hp)
register struct hole *hp; /* ptr to hole to merge with its successors */
{
/* Check for contiguous holes and merge any found. Contiguous holes can occur
* when a block of memory is freed, and it happens to abut another hole on
* either or both ends. The pointer 'hp' points to the first of a series of
* three holes that can potentially all be merged together.
*/
register struct hole *next_ptr;
/* If 'hp' points to the last hole, no merging is possible. If it does not,
* try to absorb its successor into it and free the successor's table entry.
*/
if ( (next_ptr = hp->h_next) == NULL) return;
if (hp->h_base + hp->h_len == next_ptr->h_base) {
hp->h_len += next_ptr->h_len; /* first one gets second one's mem */
del_slot(hp, next_ptr);
} else {
hp = next_ptr;
}
/* If 'hp' now points to the last hole, return; otherwise, try to absorb its
* successor into it.
*/
if ( (next_ptr = hp->h_next) == NULL) return;
if (hp->h_base + hp->h_len == next_ptr->h_base) {
hp->h_len += next_ptr->h_len;
del_slot(hp, next_ptr);
}
}
/*===========================================================================*
@ -329,16 +124,6 @@ struct memory *chunks; /* list of free memory chunks */
* are taken from the list headed by 'free_slots'.
*/
int i, first = 0;
register struct hole *hp;
/* Put all holes on the free list. */
for (hp = &hole[0]; hp < &hole[_NR_HOLES]; hp++) {
hp->h_next = hp + 1;
hp->h_base = hp->h_len = 0;
}
hole[_NR_HOLES-1].h_next = NULL;
hole_head = NULL;
free_slots = &hole[0];
addr_init(&addravl);
@ -356,8 +141,6 @@ struct memory *chunks; /* list of free memory chunks */
first = 0;
}
}
CHECKHOLES;
}
#if SANITYCHECKS