linux-kernel - [PATCH v2] net: ena: Do not waste napi skb cache

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Date:   Sat, 29 Jan 2022 08:53:36 +0000
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     netdev@...r.kernel.org
Cc:     jwiedmann.dev@...il.com, Shay Agroskin <shayagr@...zon.com>,
        Arthur Kiyanovski <akiyano@...zon.com>,
        David Arinzon <darinzon@...zon.com>,
        Noam Dagan <ndagan@...zon.com>,
        Saeed Bishara <saeedb@...zon.com>,
        "David S . Miller" <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        Sameeh Jubran <sameehj@...zon.com>,
        Wei Yongjun <weiyongjun1@...wei.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        linux-kernel@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>
Subject: [PATCH v2] net: ena: Do not waste napi skb cache

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@...il.com: Use napi_alloc_skb() instead of
  netdev_alloc_skb_ip_align() to keep things consistent. ]

Signed-off-by: Hyeonggon Yoo <42.hyeyoo@...il.com>
Acked-by: Shay Agroskin <shayagr@...zon.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