diff options
Diffstat (limited to 'kalloc.c')
| -rw-r--r-- | kalloc.c | 40 |
1 files changed, 18 insertions, 22 deletions
@@ -22,21 +22,20 @@ struct { // Initialize free list of physical pages. // This code cheats by just considering one megabyte of -// pages after _end. Real systems would determine the +// pages after end. Real systems would determine the // amount of memory available in the system and use it all. void kinit(void) { - extern int end; - uint mem; - char *start; + extern char end[]; + uint len; + char *p; initlock(&kmem.lock, "kmem"); - start = (char*) &end; - start = (char*) (((uint)start + PAGE) & ~(PAGE-1)); - mem = 256; // assume computer has 256 pages of RAM - cprintf("mem = %d\n", mem * PAGE); - kfree(start, mem * PAGE); + p = (char*)(((uint)end + PAGE) & ~(PAGE-1)); + len = 256*PAGE; // assume computer has 256 pages of RAM, 1 MB + cprintf("mem = %d\n", len); + kfree(p, len); } // Free the len bytes of memory pointed at by v, @@ -61,13 +60,7 @@ kfree(char *v, int len) rend = (struct run*)((char*)r + r->len); if(r <= p && p < rend) panic("freeing free page"); - if(pend == r){ // p next to r: replace r with p - p->len = len + r->len; - p->next = r->next; - *rp = p; - goto out; - } - if(rend == p){ // r next to p: replace p with r + if(rend == p){ // r before p: expand r to include p r->len += len; if(r->next && r->next == pend){ // r now next to r->next? r->len += r->next->len; @@ -75,6 +68,12 @@ kfree(char *v, int len) } goto out; } + if(pend == r){ // p before r: expand p to include, replace r + p->len = len + r->len; + p->next = r->next; + *rp = p; + goto out; + } } // Insert p before r in list. p->len = len; @@ -99,14 +98,11 @@ kalloc(int n) acquire(&kmem.lock); for(rp=&kmem.freelist; (r=*rp) != 0; rp=&r->next){ - if(r->len == n){ - *rp = r->next; - release(&kmem.lock); - return (char*)r; - } - if(r->len > n){ + if(r->len >= n){ r->len -= n; p = (char*)r + r->len; + if(r->len == 0) + *rp = r->next; release(&kmem.lock); return p; } |