start of name cache

731ffe8e · Robert Morris · e3f5ef60 · 731ffe8e · 731ffe8e · 731ffe8e
--- a/Makefile
+++ b/Makefile
@@ -5,6 +5,7 @@ OBJS = \
 	exec.o\
 	file.o\
 	fs.o\
+	namecache.o\
 	ide.o\
 	ioapic.o\
 	kalloc.o\

--- a/defs.h
+++ b/defs.h
@@ -43,6 +43,7 @@ int             filewrite(struct file*, char*, int n);
 int             dirlink(struct inode*, char*, uint);
 struct inode*   dirlookup(struct inode*, char*, uint*);
 struct inode*   ialloc(uint, short);
+struct inode*   iget(uint dev, uint inum);
 struct inode*   idup(struct inode*);
 void            iinit(void);
 void            ilock(struct inode*);
@@ -197,6 +198,12 @@ int             copyin(struct vmap *, uint, void*, uint);
 int             pagefault(struct vmap *, uint, uint);
 void            clearpages(pde_t *pgdir, void *begin, void *end);

+// namecache.c
+void            nc_init();
+struct inode *  nc_lookup(struct inode *, char *);
+void            nc_insert(struct inode *, char *, struct inode *);
+
+
 // number of elements in fixed-size array
 #define NELEM(x) (sizeof(x)/sizeof((x)[0]))
 #define NULL 0
--- a/fs.c
+++ b/fs.c
@@ -146,8 +146,6 @@ iinit(void)
  }
 }

-static struct inode* iget(uint dev, uint inum);
-
 //PAGEBREAK!
 // Allocate a new inode with the given type on device dev.
 struct inode*
@@ -195,7 +193,7 @@ iupdate(struct inode *ip)

 // Find the inode with number inum on device dev
 // and return the in-memory copy.
-static struct inode*
+struct inode*
 iget(uint dev, uint inum)
 {
  struct inode *ip, *empty;
@@ -587,21 +585,28 @@ namex(char *path, int nameiparent, char *name)
    ip = idup(proc->cwd);

  while((path = skipelem(path, name)) != 0){
-    ilock(ip);
-    if(ip->type != T_DIR){
-      iunlockput(ip);
-      return 0;
-    }
-    if(nameiparent && *path == '\0'){
-      // Stop one level early.
-      iunlock(ip);
-      return ip;
-    }
-    if((next = dirlookup(ip, name, 0)) == 0){
+    // XXX do we need to ilock(ip)?
+    // hopefully not, would be nice to have
+    // lock-free namecache hits.
+    next = nc_lookup(ip, name);
+    if(next == 0){
+      ilock(ip);
+      if(ip->type != T_DIR){
+        iunlockput(ip);
+        return 0;
+      }
+      if(nameiparent && *path == '\0'){
+        // Stop one level early.
+        iunlock(ip);
+        return ip;
+      }
+      if((next = dirlookup(ip, name, 0)) == 0){
+        iunlockput(ip);
+        return 0;
+      }
+      nc_insert(ip, name, next);
      iunlockput(ip);
-      return 0;
    }
-    iunlockput(ip);
    ip = next;
  }
  if(nameiparent){

--- a/kalloc.c
+++ b/kalloc.c
@@ -105,8 +105,12 @@ kalloc(void)
  }

  if (r == 0) {
+    cprintf("kalloc: out of memory");
    kmemprint();
+    return 0;
+#if 0
    panic("out of memory");
+#endif
  }

  mtrace_label_register(mtrace_label_block,
@@ -182,7 +186,7 @@ morecore(uint nu)
    nu = 512;   // we allocate nu * sizeof(Header)
  }
  p = kalloc();
-  if(p == (char*)-1)
+  if(p == 0)
    return 0;
  hp = (Header*)p;
  hp->s.size = nu;

--- a/proc.c
+++ b/proc.c
@@ -69,7 +69,7 @@ allocproc(void)

  // Allocate kernel stack if possible.
  if((p->kstack = kalloc()) == 0){
-    p->state = UNUSED;
+    kmfree(p);
    return 0;
  }
  sp = p->kstack + KSTACKSIZE;