Messages in this thread | | | Date | Thu, 23 May 2013 14:41:09 +0300 | From | "Michael S. Tsirkin" <> | Subject | Re: [net-next RFC 5/8] macvtap: eliminate linear search |
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On Thu, May 23, 2013 at 11:12:30AM +0800, Jason Wang wrote: > Linear search were used in both get_slot() and macvtap_get_queue(), this is > because: > > - macvtap didn't reshuffle the array of taps when create or destroy a queue, so > when adding a new queue, macvtap must do linear search to find a location for > the new queue. This will also complicate the TUNSETQUEUE implementation for > multiqueue API. > - the queue itself didn't track the queue index, so the we must do a linear > search in the array to find the location of a existed queue. > > The solution is straightforward: reshuffle the array and introduce a queue_index > to macvtap_queue. > > Signed-off-by: Jason Wang <jasowang@redhat.com> > --- > drivers/net/macvtap.c | 63 +++++++++++++++--------------------------------- > 1 files changed, 20 insertions(+), 43 deletions(-) > > diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c > index a36e49e..5fd341c 100644 > --- a/drivers/net/macvtap.c > +++ b/drivers/net/macvtap.c > @@ -44,6 +44,7 @@ struct macvtap_queue { > struct macvlan_dev __rcu *vlan; > struct file *file; > unsigned int flags; > + u16 queue_index; > }; > > static struct proto macvtap_proto = { > @@ -84,30 +85,10 @@ static const struct proto_ops macvtap_socket_ops; > */ > static DEFINE_SPINLOCK(macvtap_lock); > > -/* > - * get_slot: return a [unused/occupied] slot in vlan->taps[]: > - * - if 'q' is NULL, return the first empty slot; > - * - otherwise, return the slot this pointer occupies. > - */ > -static int get_slot(struct macvlan_dev *vlan, struct macvtap_queue *q) > -{ > - int i; > - > - for (i = 0; i < MAX_MACVTAP_QUEUES; i++) { > - if (rcu_dereference_protected(vlan->taps[i], > - lockdep_is_held(&macvtap_lock)) == q) > - return i; > - } > - > - /* Should never happen */ > - BUG_ON(1); > -} > - > static int macvtap_set_queue(struct net_device *dev, struct file *file, > struct macvtap_queue *q) > { > struct macvlan_dev *vlan = netdev_priv(dev); > - int index; > int err = -EBUSY; > > spin_lock(&macvtap_lock); > @@ -115,12 +96,12 @@ static int macvtap_set_queue(struct net_device *dev, struct file *file, > goto out; > > err = 0; > - index = get_slot(vlan, NULL); > rcu_assign_pointer(q->vlan, vlan); > - rcu_assign_pointer(vlan->taps[index], q); > + rcu_assign_pointer(vlan->taps[vlan->numvtaps], q); > sock_hold(&q->sk); > > q->file = file; > + q->queue_index = vlan->numvtaps; > file->private_data = q; > > vlan->numvtaps++; > @@ -140,16 +121,23 @@ out: > */ > static void macvtap_put_queue(struct macvtap_queue *q) > { > + struct macvtap_queue *nq; > struct macvlan_dev *vlan; > > spin_lock(&macvtap_lock); > vlan = rcu_dereference_protected(q->vlan, > lockdep_is_held(&macvtap_lock)); > if (vlan) { > - int index = get_slot(vlan, q); > + int index = q->queue_index; > + BUG_ON(index >= vlan->numvtaps); > > - RCU_INIT_POINTER(vlan->taps[index], NULL); > + rcu_assign_pointer(vlan->taps[index], > + vlan->taps[vlan->numvtaps - 1]); > RCU_INIT_POINTER(q->vlan, NULL); > + nq = rcu_dereference_protected(vlan->taps[index], > + lockdep_is_held(&macvtap_lock)); > + nq->queue_index = index; > + > sock_put(&q->sk);
Hmm this looks like a bug BTW: sock_put should be after no one uses this tap, so must be after synchronize_rcu. No?
> --vlan->numvtaps; > }
So: nq = rcu_dereference_protected(vlan->taps[vlan->numvtaps - 1], lockdep_is_held(&macvtap_lock)); rcu_assign_pointer(vlan->taps[index], nq);
same thing?
> @@ -182,8 +170,7 @@ static struct macvtap_queue *macvtap_get_queue(struct net_device *dev, > rxq = skb_get_rxhash(skb); > if (rxq) { > tap = rcu_dereference(vlan->taps[rxq % numvtaps]); > - if (tap) > - goto out; > + goto out; > } > > if (likely(skb_rx_queue_recorded(skb))) { > @@ -193,17 +180,10 @@ static struct macvtap_queue *macvtap_get_queue(struct net_device *dev, > rxq -= numvtaps; > > tap = rcu_dereference(vlan->taps[rxq]); > - if (tap) > - goto out; > - } > - > - /* Everything failed - find first available queue */ > - for (rxq = 0; rxq < MAX_MACVTAP_QUEUES; rxq++) { > - tap = rcu_dereference(vlan->taps[rxq]); > - if (tap) > - break; > + goto out; > } > > + tap = rcu_dereference(vlan->taps[0]); > out: > return tap; > } > @@ -221,17 +201,14 @@ static void macvtap_del_queues(struct net_device *dev) > > /* macvtap_put_queue can free some slots, so go through all slots */ > spin_lock(&macvtap_lock); > - for (i = 0; i < MAX_MACVTAP_QUEUES && vlan->numvtaps; i++) { > + for (i = 0; i < vlan->numvtaps; i++) { > q = rcu_dereference_protected(vlan->taps[i], > lockdep_is_held(&macvtap_lock)); > - if (q) { > - qlist[j++] = q; > - RCU_INIT_POINTER(vlan->taps[i], NULL); > - RCU_INIT_POINTER(q->vlan, NULL); > - vlan->numvtaps--; > - } > + BUG_ON(q == NULL); > + qlist[j++] = q; > + RCU_INIT_POINTER(vlan->taps[i], NULL); > + RCU_INIT_POINTER(q->vlan, NULL); > } > - BUG_ON(vlan->numvtaps != 0); > /* guarantee that any future macvtap_set_queue will fail */ > vlan->numvtaps = MAX_MACVTAP_QUEUES; > spin_unlock(&macvtap_lock); > -- > 1.7.1
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