mem stealing

ced61a3c · Nickolai Zeldovich · b6d8d9ad · ced61a3c · ced61a3c
--- a/kalloc.c
+++ b/kalloc.c
@@ -21,32 +21,17 @@ extern char end[]; // first address after kernel loaded from ELF file
 void
 kinit(void)
 {
-  struct run *r;
  char *p;
-  int c;
-  int n;
-  int i;

-  for (c = 0; c < NCPU; c++) {
+  for (int c = 0; c < NCPU; c++) {
    kmems[c].name[0] = (char) c;
    safestrcpy(kmems[c].name+1, "kmem", MAXNAME-1);
    initlock(&kmems[c].lock, kmems[c].name);
  }

  p = (char*)PGROUNDUP((uint)end);
-  n = (char*)PHYSTOP - p;
-  n = n / PGSIZE;
-  n = n / NCPU;
-  cprintf("n = %d end = 0x%x\n", n,  p);
-
-  for (c = 0; c < NCPU; c++) {
-    for (i = 0; i < n; i++, p += PGSIZE) {
-      memset(p, 1, PGSIZE);
-      r = (struct run*)p;
-      r->next = kmems[c].freelist;
-      kmems[c].freelist = r;
-    }
-  }
+  for(; p + PGSIZE <= (char*)PHYSTOP; p += PGSIZE)
+    kfree(p);
 }

 //PAGEBREAK: 21
@@ -69,6 +54,7 @@ kfree(char *v)
  r = (struct run*)v;
  r->next = kmem->freelist;
  kmem->freelist = r;
+  kmem->nfree++;
  mtrace_label_register(mtrace_label_block,
 			r,
 			0,
@@ -85,23 +71,33 @@ kfree(char *v)
 char*
 kalloc(void)
 {
-  struct run *r;
+  struct run *r = 0;

  //  cprintf("%d: kalloc 0x%x 0x%x 0x%x 0x%x 0%x\n", cpu->id, kmem, &kmems[cpu->id], kmem->freelist, PHYSTOP, kmems[1].freelist);

-  acquire(&kmem->lock);
-  r = kmem->freelist;
-  if(r)
-    kmem->freelist = r->next;
+  for (uint i = 0; r == 0 && i < NCPU; i++) {
+    struct kmem *m = &kmems[(i + cpunum()) % NCPU];
+    acquire(&m->lock);
+    r = m->freelist;
+    if (r) {
+      m->freelist = r->next;
+      m->nfree--;
+    }
+    release(&m->lock);
+  }
+
  mtrace_label_register(mtrace_label_block,
 			r,
 			4096,
 			"kalloc",
 			sizeof("kalloc"),
 			RET_EIP());
-  release(&kmem->lock);
-  if (r == 0)
-      cprintf("%d: kalloc out\n", cpunum());
+
+  if (r == 0) {
+    cprintf("%d: kalloc out\n", cpunum());
+    for (uint i = 0; i < NCPU; i++)
+      cprintf("cpu %d: %d free pages\n", i, kmems[i].nfree);
+  }
  memset(r, 2, PGSIZE);
  return (char*)r;
 }

--- a/kalloc.h
+++ b/kalloc.h
@@ -6,6 +6,7 @@ struct kmem {
  char name[MAXNAME];
  struct spinlock lock;
  struct run *freelist;
+  uint nfree;
 };

 extern struct kmem kmems[NCPU];