From: Eric Dumazet <eduma...@google.com>
Typical NAPI drivers use napi_consume_skb(skb) at TX completion time.
This put skb in a percpu special queue, napi_alloc_cache, to get bulk
frees.
It turns out the queue is not flushed and hits the NAPI_SKB_CACHE_SIZE
limit quite often, with skbs that were queued hundreds of usec earlier.
I measured this can take ~6000 nsec to perform one flush.
__kfree_skb_flush() can be called from two points right now :
1) From net_tx_action(), but only for skbs that were queued to
sd->completion_queue.
-> Irrelevant for NAPI drivers in normal operation.
2) From net_rx_action(), but only under high stress or if RPS/RFS has a
pending action.
This patch changes net_rx_action() to perform the flush in all cases and
after more urgent operations happened (like kicking remote CPUS for
RPS/RFS).
Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: Jesper Dangaard Brouer <bro...@redhat.com>
Cc: Alexander Duyck <alexander.h.du...@intel.com>
---
net/core/dev.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index
f71b34ab57a5132647729d20e21376d362d4e630..048b46b7c92ae10080226ea7050fad3529920baa
100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5260,7 +5260,7 @@ static __latent_entropy void net_rx_action(struct
softirq_action *h)
if (list_empty(&list)) {
if (!sd_has_rps_ipi_waiting(sd) && list_empty(&repoll))
- return;
+ goto out;
break;
}
@@ -5278,7 +5278,6 @@ static __latent_entropy void net_rx_action(struct
softirq_action *h)
}
}
- __kfree_skb_flush();
local_irq_disable();
list_splice_tail_init(&sd->poll_list, &list);
@@ -5288,6 +5287,8 @@ static __latent_entropy void net_rx_action(struct
softirq_action *h)
__raise_softirq_irqoff(NET_RX_SOFTIRQ);
net_rps_action_and_irq_enable(sd);
+out:
+ __kfree_skb_flush();
}
struct netdev_adjacent {
