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macvlan: Skip broadcast queue if multicast with single receiver
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As it stands all broadcast and multicast packets are queued and
processed in a work queue.  This is so that we don't overwhelm
the receive softirq path by generating thousands of packets or
more (see commit 412ca15 "macvlan: Move broadcasts into a
work queue").

As such all multicast packets will be delayed, even if they will
be received by a single macvlan device.  As using a workqueue
is not free in terms of latency, we should avoid this where possible.

This patch adds a new filter to determine which addresses should
be delayed and which ones won't.  This is done using a crude
counter of how many times an address has been added to the macvlan
port (ha->synced).  For now if an address has been added more than
once, then it will be considered to be broadcast.  This could be
tuned further by making this threshold configurable.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Herbert Xu authored and David S. Miller committed Mar 29, 2023
1 parent 6fc5f5b commit d45276e
Showing 1 changed file with 46 additions and 28 deletions.
74 changes: 46 additions & 28 deletions drivers/net/macvlan.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,7 @@ struct macvlan_port {
u32 flags;
int count;
struct hlist_head vlan_source_hash[MACVLAN_HASH_SIZE];
DECLARE_BITMAP(bc_filter, MACVLAN_MC_FILTER_SZ);
DECLARE_BITMAP(mc_filter, MACVLAN_MC_FILTER_SZ);
unsigned char perm_addr[ETH_ALEN];
};
Expand Down Expand Up @@ -291,6 +292,31 @@ static void macvlan_broadcast(struct sk_buff *skb,
}
}

static void macvlan_multicast_rx(const struct macvlan_port *port,
const struct macvlan_dev *src,
struct sk_buff *skb)
{
if (!src)
/* frame comes from an external address */
macvlan_broadcast(skb, port, NULL,
MACVLAN_MODE_PRIVATE |
MACVLAN_MODE_VEPA |
MACVLAN_MODE_PASSTHRU|
MACVLAN_MODE_BRIDGE);
else if (src->mode == MACVLAN_MODE_VEPA)
/* flood to everyone except source */
macvlan_broadcast(skb, port, src->dev,
MACVLAN_MODE_VEPA |
MACVLAN_MODE_BRIDGE);
else
/*
* flood only to VEPA ports, bridge ports
* already saw the frame on the way out.
*/
macvlan_broadcast(skb, port, src->dev,
MACVLAN_MODE_VEPA);
}

static void macvlan_process_broadcast(struct work_struct *w)
{
struct macvlan_port *port = container_of(w, struct macvlan_port,
Expand All @@ -308,27 +334,7 @@ static void macvlan_process_broadcast(struct work_struct *w)
const struct macvlan_dev *src = MACVLAN_SKB_CB(skb)->src;

rcu_read_lock();

if (!src)
/* frame comes from an external address */
macvlan_broadcast(skb, port, NULL,
MACVLAN_MODE_PRIVATE |
MACVLAN_MODE_VEPA |
MACVLAN_MODE_PASSTHRU|
MACVLAN_MODE_BRIDGE);
else if (src->mode == MACVLAN_MODE_VEPA)
/* flood to everyone except source */
macvlan_broadcast(skb, port, src->dev,
MACVLAN_MODE_VEPA |
MACVLAN_MODE_BRIDGE);
else
/*
* flood only to VEPA ports, bridge ports
* already saw the frame on the way out.
*/
macvlan_broadcast(skb, port, src->dev,
MACVLAN_MODE_VEPA);

macvlan_multicast_rx(port, src, skb);
rcu_read_unlock();

if (src)
Expand Down Expand Up @@ -476,8 +482,10 @@ static rx_handler_result_t macvlan_handle_frame(struct sk_buff **pskb)
}

hash = mc_hash(NULL, eth->h_dest);
if (test_bit(hash, port->mc_filter))
if (test_bit(hash, port->bc_filter))
macvlan_broadcast_enqueue(port, src, skb);
else if (test_bit(hash, port->mc_filter))
macvlan_multicast_rx(port, src, skb);

return RX_HANDLER_PASS;
}
Expand Down Expand Up @@ -780,20 +788,27 @@ static void macvlan_change_rx_flags(struct net_device *dev, int change)

static void macvlan_compute_filter(unsigned long *mc_filter,
struct net_device *dev,
struct macvlan_dev *vlan)
struct macvlan_dev *vlan, int cutoff)
{
if (dev->flags & (IFF_PROMISC | IFF_ALLMULTI)) {
bitmap_fill(mc_filter, MACVLAN_MC_FILTER_SZ);
if (cutoff >= 0)
bitmap_fill(mc_filter, MACVLAN_MC_FILTER_SZ);
else
bitmap_zero(mc_filter, MACVLAN_MC_FILTER_SZ);
} else {
struct netdev_hw_addr *ha;
DECLARE_BITMAP(filter, MACVLAN_MC_FILTER_SZ);
struct netdev_hw_addr *ha;

bitmap_zero(filter, MACVLAN_MC_FILTER_SZ);
netdev_for_each_mc_addr(ha, dev) {
if (cutoff >= 0 && ha->synced <= cutoff)
continue;

__set_bit(mc_hash(vlan, ha->addr), filter);
}

__set_bit(mc_hash(vlan, dev->broadcast), filter);
if (cutoff >= 0)
__set_bit(mc_hash(vlan, dev->broadcast), filter);

bitmap_copy(mc_filter, filter, MACVLAN_MC_FILTER_SZ);
}
Expand All @@ -803,7 +818,7 @@ static void macvlan_set_mac_lists(struct net_device *dev)
{
struct macvlan_dev *vlan = netdev_priv(dev);

macvlan_compute_filter(vlan->mc_filter, dev, vlan);
macvlan_compute_filter(vlan->mc_filter, dev, vlan, 0);

dev_uc_sync(vlan->lowerdev, dev);
dev_mc_sync(vlan->lowerdev, dev);
Expand All @@ -821,7 +836,10 @@ static void macvlan_set_mac_lists(struct net_device *dev)
* The solution is to maintain a list of broadcast addresses like
* we do for uc/mc, if you care.
*/
macvlan_compute_filter(vlan->port->mc_filter, vlan->lowerdev, NULL);
macvlan_compute_filter(vlan->port->mc_filter, vlan->lowerdev, NULL,
0);
macvlan_compute_filter(vlan->port->bc_filter, vlan->lowerdev, NULL,
1);
}

static int macvlan_change_mtu(struct net_device *dev, int new_mtu)
Expand Down

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