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Commit 323ebb61 authored by Edward Cree's avatar Edward Cree Committed by David S. Miller
Browse files

net: use listified RX for handling GRO_NORMAL skbs 



When GRO decides not to coalesce a packet, in napi_frags_finish(), instead
 of passing it to the stack immediately, place it on a list in the napi
 struct.  Then, at flush time (napi_complete_done(), napi_poll(), or
 napi_busy_loop()), call netif_receive_skb_list_internal() on the list.
We'd like to do that in napi_gro_flush(), but it's not called if
 !napi->gro_bitmask, so we have to do it in the callers instead.  (There are
 a handful of drivers that call napi_gro_flush() themselves, but it's not
 clear why, or whether this will affect them.)
Because a full 64 packets is an inefficiently large batch, also consume the
 list whenever it exceeds gro_normal_batch, a new net/core sysctl that
 defaults to 8.

Signed-off-by: default avatarEdward Cree <ecree@solarflare.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 67270136

include/linux/netdevice.h

+3 −0
Original line number Diff line number Diff line
@@ -332,6 +332,8 @@ struct napi_struct { 
	struct net_device	*dev;

	struct gro_list		gro_hash[GRO_HASH_BUCKETS];

	struct sk_buff		*skb;

	struct list_head	rx_list; /* Pending GRO_NORMAL skbs */

	int			rx_count; /* length of rx_list */

	struct hrtimer		timer;

	struct list_head	dev_list;

	struct hlist_node	napi_hash_node;
@@ -4239,6 +4241,7 @@ extern int dev_weight_rx_bias; 
extern int		dev_weight_tx_bias;

extern int		dev_rx_weight;

extern int		dev_tx_weight;

extern int		gro_normal_batch;



bool netdev_has_upper_dev(struct net_device *dev, struct net_device *upper_dev);

struct net_device *netdev_upper_get_next_dev_rcu(struct net_device *dev,

net/core/dev.c

+41 −3
Original line number Diff line number Diff line
@@ -3963,6 +3963,8 @@ int dev_weight_rx_bias __read_mostly = 1; /* bias for backlog weight */ 
int dev_weight_tx_bias __read_mostly = 1;  /* bias for output_queue quota */

int dev_rx_weight __read_mostly = 64;

int dev_tx_weight __read_mostly = 64;

/* Maximum number of GRO_NORMAL skbs to batch up for list-RX */

int gro_normal_batch __read_mostly = 8;



/* Called with irq disabled */

static inline void ____napi_schedule(struct softnet_data *sd,
@@ -5747,6 +5749,26 @@ struct sk_buff *napi_get_frags(struct napi_struct *napi) 
}

EXPORT_SYMBOL(napi_get_frags);



/* Pass the currently batched GRO_NORMAL SKBs up to the stack. */

static void gro_normal_list(struct napi_struct *napi)

{

	if (!napi->rx_count)

		return;

	netif_receive_skb_list_internal(&napi->rx_list);

	INIT_LIST_HEAD(&napi->rx_list);

	napi->rx_count = 0;

}



/* Queue one GRO_NORMAL SKB up for list processing.  If batch size exceeded,

 * pass the whole batch up to the stack.

 */

static void gro_normal_one(struct napi_struct *napi, struct sk_buff *skb)

{

	list_add_tail(&skb->list, &napi->rx_list);

	if (++napi->rx_count >= gro_normal_batch)

		gro_normal_list(napi);

}



static gro_result_t napi_frags_finish(struct napi_struct *napi,

				      struct sk_buff *skb,

				      gro_result_t ret)
@@ -5756,8 +5778,8 @@ static gro_result_t napi_frags_finish(struct napi_struct *napi, 
	case GRO_HELD:

		__skb_push(skb, ETH_HLEN);

		skb->protocol = eth_type_trans(skb, skb->dev);

		if (ret == GRO_NORMAL && netif_receive_skb_internal(skb))

			ret = GRO_DROP;

		if (ret == GRO_NORMAL)

			gro_normal_one(napi, skb);

		break;



	case GRO_DROP:
@@ -6034,6 +6056,8 @@ bool napi_complete_done(struct napi_struct *n, int work_done) 
				 NAPIF_STATE_IN_BUSY_POLL)))

		return false;



	gro_normal_list(n);



	if (n->gro_bitmask) {

		unsigned long timeout = 0;
@@ -6119,10 +6143,19 @@ static void busy_poll_stop(struct napi_struct *napi, void *have_poll_lock) 
	 * Ideally, a new ndo_busy_poll_stop() could avoid another round.

	 */

	rc = napi->poll(napi, BUSY_POLL_BUDGET);

	/* We can't gro_normal_list() here, because napi->poll() might have

	 * rearmed the napi (napi_complete_done()) in which case it could

	 * already be running on another CPU.

	 */

	trace_napi_poll(napi, rc, BUSY_POLL_BUDGET);

	netpoll_poll_unlock(have_poll_lock);

	if (rc == BUSY_POLL_BUDGET)

	if (rc == BUSY_POLL_BUDGET) {

		/* As the whole budget was spent, we still own the napi so can

		 * safely handle the rx_list.

		 */

		gro_normal_list(napi);

		__napi_schedule(napi);

	}

	local_bh_enable();

}
@@ -6167,6 +6200,7 @@ void napi_busy_loop(unsigned int napi_id, 
		}

		work = napi_poll(napi, BUSY_POLL_BUDGET);

		trace_napi_poll(napi, work, BUSY_POLL_BUDGET);

		gro_normal_list(napi);

count:

		if (work > 0)

			__NET_ADD_STATS(dev_net(napi->dev),
@@ -6272,6 +6306,8 @@ void netif_napi_add(struct net_device *dev, struct napi_struct *napi, 
	napi->timer.function = napi_watchdog;

	init_gro_hash(napi);

	napi->skb = NULL;

	INIT_LIST_HEAD(&napi->rx_list);

	napi->rx_count = 0;

	napi->poll = poll;

	if (weight > NAPI_POLL_WEIGHT)

		netdev_err_once(dev, "%s() called with weight %d\n", __func__,
@@ -6368,6 +6404,8 @@ static int napi_poll(struct napi_struct *n, struct list_head *repoll) 
		goto out_unlock;

	}



	gro_normal_list(n);



	if (n->gro_bitmask) {

		/* flush too old packets

		 * If HZ < 1000, flush all packets.

net/core/sysctl_net_core.c

+8 −0
Original line number Diff line number Diff line
@@ -567,6 +567,14 @@ static struct ctl_table net_core_table[] = { 
		.mode		= 0644,

		.proc_handler	= proc_do_static_key,

	},

	{

		.procname	= "gro_normal_batch",

		.data		= &gro_normal_batch,

		.maxlen		= sizeof(unsigned int),

		.mode		= 0644,

		.proc_handler	= proc_dointvec_minmax,

		.extra1		= SYSCTL_ONE,

	},

	{ }

};