keep track of inode cache size

d5fd5fdd · Nickolai Zeldovich · 022104b1 · d5fd5fdd
--- a/fs.c
+++ b/fs.c
@@ -133,18 +133,14 @@ bfree(int dev, uint b)

 static struct ns *ins;

+static struct { uint x __attribute__((aligned (CACHELINE))); } icache_free[NCPU];
+
 void
 iinit(void)
 {
  ins = nsalloc(0);
-  for (int i = 0; i < NINODE; i++) {
-    struct inode *ip = kmalloc(sizeof(*ip));
-    memset(ip, 0, sizeof(*ip));
-    ip->inum = -i-1;
-    initlock(&ip->lock, "icache-lock");
-    initcondvar(&ip->cv, "icache-cv");
-    ns_insert(ins, KII(ip->dev, ip->inum), ip);
-  }
+  for (int i = 0; i < NCPU; i++)
+    icache_free[i].x = NINODE;
 }

 //PAGEBREAK!
@@ -271,6 +267,8 @@ iget(uint dev, uint inum)
  // Allocate fresh inode cache slot.
 retry_evict:
  (void) 0;
+  uint cur_free = icache_free[cpu->id].x;
+  if (cur_free == 0) {
    struct inode *victim = ns_enumerate(ins, evict, 0);
    if (!victim)
      panic("iget out of space");
@@ -284,6 +282,10 @@ iget(uint dev, uint inum)
    release(&victim->lock);
    ns_remove(ins, KII(victim->dev, victim->inum), victim);
    rcu_delayed(victim, ifree);
+  } else {
+    if (!__sync_bool_compare_and_swap(&icache_free[cpu->id].x, cur_free, cur_free-1))
+      goto retry_evict;
+  }

  ip = kmalloc(sizeof(*ip));
  ip->dev = dev;
@@ -380,6 +382,8 @@ iput(struct inode *ip)
 	release(&ip->lock);
 	return;
      }
+      release(&ip->lock);
+      ns_remove(ins, KII(ip->dev, ip->inum), ip);

      itrunc(ip);
      ip->type = 0;
@@ -388,9 +392,8 @@ iput(struct inode *ip)
      ip->gen += 1;
      iupdate(ip);

-      release(&ip->lock);
-      ns_remove(ins, KII(ip->dev, ip->inum), ip);
      rcu_delayed(ip, ifree);
+      __sync_fetch_and_add(&icache_free[cpu->id].x, 1);
      return;
    }
    release(&ip->lock);