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net: use listified RX for handling GRO_NORMAL skbs

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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: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Edward Cree 2019-08-06 14:53:55 +01:00 committed by David S. Miller
parent 6727013694
commit 323ebb61e3
3 changed files with 52 additions and 3 deletions
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3
include/linux/netdevice.h
View File

@ -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,

44
net/core/dev.c
View File

@ -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 @@ restart:
}
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.

8
net/core/sysctl_net_core.c
View File

@ -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,
},
{ }
};