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kalloc/kfree now only a page at a time

do not keep sorted contiguous free list
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1 parent 81b30b1 commit 7d7dc9331bf33f77c9c3a71350782dadae8dd371 Robert Morris committed Aug 31, 2010
Showing with 46 additions and 91 deletions.
  1. +2 −3 defs.h
  2. +23 −66 kalloc.c
  3. +2 −2 main.c
  4. +1 −1 mmu.h
  5. +2 −2 param.h
  6. +3 −3 pipe.c
  7. +3 −3 proc.c
  8. +2 −2 umalloc.c
  9. +8 −9 vm.c
View
5 defs.h
@@ -60,9 +60,8 @@ extern uchar ioapicid;
void ioapicinit(void);
// kalloc.c
-extern int nfreemem;
-char* kalloc(int);
-void kfree(char*, int);
+char* kalloc(void);
+void kfree(char*);
void kinit(char*,uint);
// kbd.c
View
@@ -1,8 +1,6 @@
// Physical memory allocator, intended to allocate
-// memory for user processes. Allocates in 4096-byte pages.
-// Free list is kept sorted and combines adjacent pages into
-// long runs, to make it easier to allocate big segments.
-// This combining is not useful now that xv6 uses paging.
+// memory for user processes, kernel stacks, page table pages,
+// and pipe buffers. Allocates 4096-byte pages.
#include "types.h"
#include "defs.h"
@@ -12,100 +10,59 @@
struct run {
struct run *next;
- int len; // bytes
};
struct {
struct spinlock lock;
struct run *freelist;
} kmem;
-int nfreemem;
-
// Initialize free list of physical pages.
void
kinit(char *p, uint len)
{
initlock(&kmem.lock, "kmem");
- nfreemem = 0;
- kfree(p, len);
+ char *p1 = (char*)PGROUNDUP((uint)p);
+ char *p2 = PGROUNDDOWN(p + len);
+ for( ; p1 < p2; p1 += 4096)
+ kfree(p1);
}
-// Free the len bytes of memory pointed at by v,
+// Free the page of physical memory pointed at by v,
// which normally should have been returned by a
-// call to kalloc(len). (The exception is when
+// call to kalloc(). (The exception is when
// initializing the allocator; see kinit above.)
void
-kfree(char *v, int len)
+kfree(char *v)
{
- struct run *r, *rend, **rp, *p, *pend;
+ struct run *r;
- if(len <= 0 || len % PGSIZE)
+ if(((uint) v) % PGSIZE || (uint)v < 1024*1024 || (uint)v >= PHYSTOP)
panic("kfree");
// Fill with junk to catch dangling refs.
- memset(v, 1, len);
+ memset(v, 1, PGSIZE);
acquire(&kmem.lock);
- nfreemem += len;
- p = (struct run*)v;
- pend = (struct run*)(v + len);
- for(rp=&kmem.freelist; (r=*rp) != 0 && r <= pend; rp=&r->next){
- rend = (struct run*)((char*)r + r->len);
- if(r <= p && p < rend) {
- cprintf("freeing a free page: r = 0x%x p = 0x%x rend = 0x%x\n",
- r, p, rend);
- panic("freeing free page");
- }
- 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;
- r->next = r->next->next;
- }
- 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;
- p->next = r;
- *rp = p;
-
- out:
+ r = (struct run *) v;
+ r->next = kmem.freelist;
+ kmem.freelist = r;
release(&kmem.lock);
}
-// Allocate n bytes of physical memory.
-// Returns a kernel-segment pointer.
+// Allocate one 4096-byte page of physical memory.
+// Returns a pointer that the kernel can use.
// Returns 0 if the memory cannot be allocated.
char*
-kalloc(int n)
+kalloc()
{
- char *p;
- struct run *r, **rp;
-
- if(n % PGSIZE || n <= 0)
- panic("kalloc");
+ struct run *r;
acquire(&kmem.lock);
- for(rp=&kmem.freelist; (r=*rp) != 0; rp=&r->next){
- if(r->len >= n){
- r->len -= n;
- p = (char*)r + r->len;
- if(r->len == 0)
- *rp = r->next;
- nfreemem -= n;
- release(&kmem.lock);
- return p;
- }
- }
+ r = kmem.freelist;
+ if(r)
+ kmem.freelist = r->next;
release(&kmem.lock);
- return 0;
+ return (char*) r;
}
View
4 main.c
@@ -28,7 +28,7 @@ main(void)
void
jkstack(void)
{
- char *kstack = kalloc(PGSIZE);
+ char *kstack = kalloc();
if (!kstack)
panic("jkstack\n");
char *top = kstack + PGSIZE;
@@ -92,7 +92,7 @@ bootothers(void)
continue;
// Fill in %esp, %eip and start code on cpu.
- stack = kalloc(KSTACKSIZE);
+ stack = kalloc();
*(void**)(code-4) = stack + KSTACKSIZE;
*(void**)(code-8) = mpmain;
lapicstartap(c->id, (uint)code);
View
2 mmu.h
@@ -112,7 +112,7 @@ struct segdesc {
#define PDXSHIFT 22 // offset of PDX in a linear address
#define PGROUNDUP(sz) (((sz)+PGSIZE-1) & ~(PGSIZE-1))
-#define PGROUNDDOWN(a) ((char*)((((unsigned int)a) & ~(PGSIZE-1))))
+#define PGROUNDDOWN(a) ((char*)((((unsigned int)(a)) & ~(PGSIZE-1))))
// Page table/directory entry flags.
#define PTE_P 0x001 // Present
View
@@ -1,10 +1,10 @@
#define NPROC 64 // maximum number of processes
-#define PAGE 4096 // conveniently chosen to be equal to PGSIZE
-#define KSTACKSIZE PAGE // size of per-process kernel stack
+#define KSTACKSIZE 4096 // size of per-process kernel stack
#define NCPU 8 // maximum number of CPUs
#define NOFILE 16 // open files per process
#define NFILE 100 // open files per system
#define NBUF 10 // size of disk block cache
#define NINODE 50 // maximum number of active i-nodes
#define NDEV 10 // maximum major device number
#define ROOTDEV 1 // device number of file system root disk
+#define PHYSTOP 0x1000000 // use phys mem up to here as free pool
View
6 pipe.c
@@ -27,7 +27,7 @@ pipealloc(struct file **f0, struct file **f1)
*f0 = *f1 = 0;
if((*f0 = filealloc()) == 0 || (*f1 = filealloc()) == 0)
goto bad;
- if((p = (struct pipe*)kalloc(PAGE)) == 0)
+ if((p = (struct pipe*)kalloc()) == 0)
goto bad;
p->readopen = 1;
p->writeopen = 1;
@@ -47,7 +47,7 @@ pipealloc(struct file **f0, struct file **f1)
//PAGEBREAK: 20
bad:
if(p)
- kfree((char*)p, PAGE);
+ kfree((char*)p);
if(*f0)
fileclose(*f0);
if(*f1)
@@ -68,7 +68,7 @@ pipeclose(struct pipe *p, int writable)
}
if(p->readopen == 0 && p->writeopen == 0) {
release(&p->lock);
- kfree((char*)p, PAGE);
+ kfree((char*)p);
} else
release(&p->lock);
}
View
6 proc.c
@@ -84,7 +84,7 @@ allocproc(void)
release(&ptable.lock);
// Allocate kernel stack if possible.
- if((p->kstack = kalloc(KSTACKSIZE)) == 0){
+ if((p->kstack = kalloc()) == 0){
p->state = UNUSED;
return 0;
}
@@ -169,7 +169,7 @@ fork(void)
// Copy process state from p.
if (!(np->pgdir = copyuvm(proc->pgdir, proc->sz))) {
- kfree(np->kstack, KSTACKSIZE);
+ kfree(np->kstack);
np->kstack = 0;
np->state = UNUSED;
return -1;
@@ -418,7 +418,7 @@ wait(void)
if(p->state == ZOMBIE){
// Found one.
pid = p->pid;
- kfree(p->kstack, KSTACKSIZE);
+ kfree(p->kstack);
p->kstack = 0;
freevm(p->pgdir);
p->state = UNUSED;
View
@@ -49,8 +49,8 @@ morecore(uint nu)
char *p;
Header *hp;
- if(nu < PAGE)
- nu = PAGE;
+ if(nu < 4096)
+ nu = 4096;
p = sbrk(nu * sizeof(Header));
if(p == (char*) -1)
return 0;
View
17 vm.c
@@ -29,7 +29,6 @@
// (both in physical memory and in the kernel's virtual address
// space).
-#define PHYSTOP 0x1000000
#define USERTOP 0xA0000
static uint kerntext; // Linker starts kernel at 1MB
@@ -53,7 +52,7 @@ walkpgdir(pde_t *pgdir, const void *va, int create)
pde = &pgdir[PDX(va)];
if (*pde & PTE_P) {
pgtab = (pte_t*) PTE_ADDR(*pde);
- } else if (!create || !(r = (uint) kalloc(PGSIZE)))
+ } else if (!create || !(r = (uint) kalloc()))
return 0;
else {
pgtab = (pte_t*) r;
@@ -156,7 +155,7 @@ setupkvm(void)
pde_t *pgdir;
// Allocate page directory
- if (!(pgdir = (pde_t *) kalloc(PGSIZE)))
+ if (!(pgdir = (pde_t *) kalloc()))
return 0;
memset(pgdir, 0, PGSIZE);
// Map IO space from 640K to 1Mbyte
@@ -206,7 +205,7 @@ allocuvm(pde_t *pgdir, char *addr, uint sz)
for(a = first; a <= last; a += PGSIZE){
pte_t *pte = walkpgdir(pgdir, a, 0);
if(pte == 0 || (*pte & PTE_P) == 0){
- char *mem = kalloc(PGSIZE);
+ char *mem = kalloc();
if(mem == 0){
// XXX clean up?
return 0;
@@ -235,7 +234,7 @@ deallocuvm(pde_t *pgdir, char *addr, uint sz)
uint pa = PTE_ADDR(*pte);
if(pa == 0)
panic("deallocuvm");
- kfree((void *) pa, PGSIZE);
+ kfree((void *) pa);
*pte = 0;
}
}
@@ -260,15 +259,15 @@ freevm(pde_t *pgdir)
uint pa = PTE_ADDR(pgtab[j]);
uint va = PGADDR(i, j, 0);
if (va < USERTOP) // user memory
- kfree((void *) pa, PGSIZE);
+ kfree((void *) pa);
pgtab[j] = 0;
}
}
- kfree((void *) da, PGSIZE);
+ kfree((void *) da);
pgdir[i] = 0;
}
}
- kfree((void *) pgdir, PGSIZE);
+ kfree((void *) pgdir);
}
int
@@ -324,7 +323,7 @@ copyuvm(pde_t *pgdir, uint sz)
panic("copyuvm: pte should exist\n");
if(*pte & PTE_P){
pa = PTE_ADDR(*pte);
- if (!(mem = kalloc(PGSIZE)))
+ if (!(mem = kalloc()))
return 0;
memmove(mem, (char *)pa, PGSIZE);
if (!mappages(d, (void *)i, PGSIZE, PADDR(mem), PTE_W|PTE_U))

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