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Date: Mon, 24 Jan 2022 11:29:52 +0200 From: Julian Wiedmann <jwiedmann.dev@...il.com> To: Hyeonggon Yoo <42.hyeyoo@...il.com>, netdev@...r.kernel.org Cc: 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>, Jakub Kicinski <kuba@...nel.org>, 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 Subject: Re: [PATCH] net: ena: Do not waste napi skb cache On 24.01.22 10:57, Julian Wiedmann wrote: > On 23.01.22 13:56, 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() >> instead of build_skb() to when allocating skb. >> >> This patch was tested on aws a1.metal instance. >> >> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@...il.com> >> --- >> drivers/net/ethernet/amazon/ena/ena_netdev.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c >> index c72f0c7ff4aa..2c67fb1703c5 100644 >> --- a/drivers/net/ethernet/amazon/ena/ena_netdev.c >> +++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c >> @@ -1407,7 +1407,7 @@ static struct sk_buff *ena_alloc_skb(struct ena_ring *rx_ring, void *first_frag) >> skb = netdev_alloc_skb_ip_align(rx_ring->netdev, >> rx_ring->rx_copybreak); > > To keep things consistent, this should then also be napi_alloc_skb(). > And on closer look, this copybreak path also looks buggy. If rx_copybreak gets reduced _while_ receiving a frame, the allocated skb can end up too small to take all the data. @ ena maintainers: can you please fix this? >> 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, >
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