Re: [net-next RFC PATCH 4/7] tuntap: multiqueue support

----- Original Message -----

Le vendredi 12 août 2011 à 09:55 +0800, Jason Wang a écrit :

quoted

+ rxq = skb_get_rxhash(skb);
+ if (rxq) {
+ tfile = rcu_dereference(tun->tfiles[rxq % numqueues]);
+ if (tfile)
+ goto out;
+ }

You can avoid an expensive divide with following trick :

u32 idx = ((u64)rxq * numqueues) >> 32;

Sure.

quoted

-static struct tun_struct *tun_get(struct file *file)
+static void tun_detach_all(struct net_device *dev)
 {
- return __tun_get(file->private_data);
+ struct tun_struct *tun = netdev_priv(dev);
+ struct tun_file *tfile, *tfile_list[MAX_TAP_QUEUES];
+ int i, j = 0;
+
+ spin_lock(&tun_lock);
+
+ for (i = 0; i < MAX_TAP_QUEUES && tun->numqueues; i++) {
+ tfile = rcu_dereference_protected(tun->tfiles[i],
+ lockdep_is_held(&tun_lock));
+ if (tfile) {
+ wake_up_all(&tfile->wq.wait);
+ tfile_list[i++] = tfile;

typo here, you want tfile_list[j++] = tfile;

Yes, thanks for catching this.

quoted

+ rcu_assign_pointer(tun->tfiles[i], NULL);
+ rcu_assign_pointer(tfile->tun, NULL);
+ --tun->numqueues;
+ }
+ }
+ BUG_ON(tun->numqueues != 0);
+ spin_unlock(&tun_lock);
+
+ synchronize_rcu();
+ for(--j; j >= 0; j--)
+ sock_put(&tfile_list[j]->sk);
 }

Could you take a look at net/packet/af_packet.c, to check how David
did
the whole fanout thing ?

__fanout_unlink()

Trick is to not leave NULL entries in the tun->tfiles[] array.

It makes things easier in hot path.

Sure I would go to take a look at this.

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