Zero pages less often

9059c14f · Silas Boyd-Wickizer · 2e184ff9 · 9059c14f · 9059c14f
--- a/include/vm.hh
+++ b/include/vm.hh
@@ -31,7 +31,7 @@ struct vmnode {
  void decref();
  void incref();
  u64 ref();
-  int allocpg();
+  int allocpg(bool zero = true);
  vmnode* copy();

  int demand_load();

--- a/kernel/vm.cc
+++ b/kernel/vm.cc
@@ -32,7 +32,7 @@ vmnode::vmnode(u64 npg, vmntype ntype, inode *i, u64 off, u64 s)
    panic("vmnode too big\n");
  memset(page, 0, npg * sizeof(page[0]));
  if (type == EAGER && ip) {
-    assert(allocpg() == 0);
+    assert(allocpg(false) == 0);
    assert(demand_load() == 0);
  }
 }
@@ -66,20 +66,29 @@ vmnode::ref(void)
 }

 int
-vmnode::allocpg()
+vmnode::allocpg(bool zero)
 {
  for(u64 i = 0; i < npages; i++) {
    if (page[i])
      continue;

-    char *p = zalloc("(vmnode::allocpg)");
+    char *p;
+    if (zero)
+      p = zalloc("(vmnode::allocpg)");
+    else
+      p = kalloc("(vmnode::allocpg)");
+
    if (!p) {
-      cprintf("allocpg: out of memory, leaving half-filled vmnode\n");
+      cprintf("allocpg: OOM -- leaving half-filled vmnode\n");
      return -1;
    }

-    if(!cmpxch(&page[i], (char*) 0, p))
-      zfree(p);
+    if(!cmpxch(&page[i], (char*) 0, p)) {
+      if (zero)
+        zfree(p);
+      else
+        kfree(p);
+    }
  }
  return 0;
 }
@@ -96,7 +105,7 @@ vmnode::copy()
  if (!page[0])   // If first page is absent, all pages are absent
    return c;

-  if (c->allocpg() < 0) {
+  if (c->allocpg(false) < 0) {
    cprintf("vmn_copy: out of memory\n");
    delete c;
    return 0;