The dumbest scalable inode allocator.

Split the inode space into per-cpu spaces of size IPB that start at the begining of a block. Block awareness is important to avoid contention on blocks themselves when allocating or freeing an inode and updating on-disk structures. That is, I don't want to make bio scalable.

The dumbest scalable inode allocator.
dee65e58 · Silas Boyd-Wickizer · a16be914 · dee65e58
--- a/kernel/fs.cc
+++ b/kernel/fs.cc
@@ -166,6 +166,17 @@ initinode(void)
  if (ins->insert(make_pair(the_root->dev, the_root->inum), the_root) < 0)
    panic("initinode: insert the_root failed");
  the_root->init();
+  if (VERBOSE) {
+    struct superblock sb;
+    u64 blocks;
+    readsb(ROOTDEV, &sb);
+    blocks = sb.ninodes/IPB;
+    cprintf("initinode: %lu inode blocks (%lu / core)\n",
+            blocks, blocks/NCPU);
+  }
 }
 //PAGEBREAK!
@@ -174,33 +185,36 @@ initinode(void)
 struct inode*
 ialloc(u32 dev, short type)
 {
-  int inum;
  struct buf *bp;
  struct dinode *dip;
  struct superblock sb;
  readsb(dev, &sb);
-  for(inum = 1; inum < sb.ninodes; inum++){  // loop over inode blocks
+  for (int k = mycpuid()*IPB; k < sb.ninodes; k += (NCPU*IPB)) {
-    bp = bread(dev, IBLOCK(inum), 0);
+    for(int inum = k; inum < k+IPB && inum < sb.ninodes; inum++){
-    dip = (struct dinode*)bp->data + inum%IPB;
+      if (inum == 0)
-    int seemsfree = (dip->type == 0);
+        continue;
-    brelse(bp, 0);
+      bp = bread(dev, IBLOCK(inum), 0);
-    if(seemsfree){
+      dip = (struct dinode*)bp->data + inum%IPB;
-      // maybe this inode is free. look at it via the
+      int seemsfree = (dip->type == 0);
-      // inode cache to make sure.
+      brelse(bp, 0);
-      struct inode *ip = iget(dev, inum);
+      if(seemsfree){
-      assert(ip->valid());
+        // maybe this inode is free. look at it via the
-      ilock(ip, 1);
+        // inode cache to make sure.
-      if(ip->type == 0){
+        struct inode *ip = iget(dev, inum);
-        ip->type = type;
+        assert(ip->valid());
-        ip->gen += 1;
+        ilock(ip, 1);
-        if(ip->nlink() || ip->size || ip->addrs[0])
+        if(ip->type == 0){
-          panic("ialloc not zeroed");
+          ip->type = type;
-        iupdate(ip);
+          ip->gen += 1;
-        return ip;
+          if(ip->nlink() || ip->size || ip->addrs[0])
+            panic("ialloc not zeroed");
+          iupdate(ip);
+          return ip;
+        }
+        iunlockput(ip);
+        //cprintf("ialloc oops %d\n", inum); // XXX harmless
      }
-      iunlockput(ip);
-      //cprintf("ialloc oops %d\n", inum); // XXX harmless
    }
  }
  cprintf("ialloc: 0/%u inodes\n", sb.ninodes);