By profiling, discovered that ena device driver allocates skb by
build_skb() and frees by napi_skb_cache_put(). Because the driver
does not use napi skb cache in allocation path, napi skb cache is
periodically filled and flushed. This is waste of napi skb cache.

As ena_alloc_skb() is called only in napi, Use napi_build_skb()
and napi_alloc_skb() when allocating skb.

This patch was tested on aws a1.metal instance.

[ jwiedmann.dev@gmail.com: Use napi_alloc_skb() instead of
  netdev_alloc_skb_ip_align() to keep things consistent. ]

Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
---
 drivers/net/ethernet/amazon/ena/ena_netdev.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
index 53080fd143dc..07444aead3fd 100644
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
@@ -1400,10 +1400,9 @@ static struct sk_buff *ena_alloc_skb(struct ena_ring *rx_ring, void *first_frag)
 	struct sk_buff *skb;
 
 	if (!first_frag)
-		skb = netdev_alloc_skb_ip_align(rx_ring->netdev,
-						rx_ring->rx_copybreak);
+		skb = napi_alloc_skb(rx_ring->napi, rx_ring->rx_copybreak);
 	else
-		skb = build_skb(first_frag, ENA_PAGE_SIZE);
+		skb = napi_build_skb(first_frag, ENA_PAGE_SIZE);
 
 	if (unlikely(!skb)) {
 		ena_increase_stat(&rx_ring->rx_stats.skb_alloc_fail, 1,
-- 
2.33.1

Hyeonggon Yoo <42.hyeyoo@gmail.com> writes:

> CAUTION: This email originated from outside of the 
> organization. Do not click links or open attachments unless you 
> can confirm the sender and know the content is safe.
>
>
>
> By profiling, discovered that ena device driver allocates skb by
> build_skb() and frees by napi_skb_cache_put(). Because the 
> driver
> does not use napi skb cache in allocation path, napi skb cache 
> is
> periodically filled and flushed. This is waste of napi skb 
> cache.
>
> As ena_alloc_skb() is called only in napi, Use napi_build_skb()
> and napi_alloc_skb() when allocating skb.
>
> This patch was tested on aws a1.metal instance.
>
> [ jwiedmann.dev@gmail.com: Use napi_alloc_skb() instead of
>   netdev_alloc_skb_ip_align() to keep things consistent. ]
>
> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> ---
>  drivers/net/ethernet/amazon/ena/ena_netdev.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>

Thank you for this work

Acked-by: Shay Agroskin <shayagr@amazon.com>

On Wed, 26 Jan 2022 13:16:41 +0000 Hyeonggon Yoo wrote:
> By profiling, discovered that ena device driver allocates skb by
> build_skb() and frees by napi_skb_cache_put(). Because the driver
> does not use napi skb cache in allocation path, napi skb cache is
> periodically filled and flushed. This is waste of napi skb cache.
> 
> As ena_alloc_skb() is called only in napi, Use napi_build_skb()
> and napi_alloc_skb() when allocating skb.
> 
> This patch was tested on aws a1.metal instance.
> 
> [ jwiedmann.dev@gmail.com: Use napi_alloc_skb() instead of
>   netdev_alloc_skb_ip_align() to keep things consistent. ]
> 
> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>

It seems you missed CCing netdev@, you'll need to repost.
You can keep the ack from Shay.