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[91.129.103.86]) by smtp.gmail.com with ESMTPSA id n15sm454493lfi.101.2022.01.24.01.29.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Jan 2022 01:29:54 -0800 (PST) Message-ID: <5cca8bdd-bed0-f26a-6c96-d18947d3a50b@gmail.com> Date: Mon, 24 Jan 2022 11:29:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [PATCH] net: ena: Do not waste napi skb cache Content-Language: en-US From: Julian Wiedmann To: Hyeonggon Yoo <42.hyeyoo@gmail.com>, netdev@vger.kernel.org Cc: Shay Agroskin , Arthur Kiyanovski , David Arinzon , Noam Dagan , Saeed Bishara , "David S . Miller" , Jakub Kicinski , Daniel Borkmann , Sameeh Jubran , Wei Yongjun , Lorenzo Bianconi , linux-kernel@vger.kernel.org References: <20220123115623.94843-1-42.hyeyoo@gmail.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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@gmail.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, >