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Tue, 08 Sep 2020 02:45:19 -0700 (PDT) Subject: Re: [PATCH bpf-next 4/4] ixgbe, xsk: use XSK_NAPI_WEIGHT as NAPI poll budget To: =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , ast@kernel.org, daniel@iogearbox.net, netdev@vger.kernel.org, bpf@vger.kernel.org Cc: =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , magnus.karlsson@intel.com, kuba@kernel.org, intel-wired-lan@lists.osuosl.org References: <20200907150217.30888-1-bjorn.topel@gmail.com> <20200907150217.30888-5-bjorn.topel@gmail.com> From: Eric Dumazet Message-ID: <6bbf1793-d2be-b724-eec4-65546d4cbc9c@gmail.com> Date: Tue, 8 Sep 2020 11:45:13 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200907150217.30888-5-bjorn.topel@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 9/7/20 5:02 PM, Björn Töpel wrote: > From: Björn Töpel > > Start using XSK_NAPI_WEIGHT as NAPI poll budget for the AF_XDP Rx > zero-copy path. > > Signed-off-by: Björn Töpel > --- > drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c > index 3771857cf887..f32c1ba0d237 100644 > --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c > +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c > @@ -239,7 +239,7 @@ int ixgbe_clean_rx_irq_zc(struct ixgbe_q_vector *q_vector, > bool failure = false; > struct sk_buff *skb; > > - while (likely(total_rx_packets < budget)) { > + while (likely(total_rx_packets < XSK_NAPI_WEIGHT)) { > union ixgbe_adv_rx_desc *rx_desc; > struct ixgbe_rx_buffer *bi; > unsigned int size This is a violation of NAPI API. IXGBE is already diverging a bit from best practices. There are reasons we want to control the budget from callers, if you want bigger budget just increase it instead of using your own ? I would rather use a generic patch. diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 7bd4fcdd0738a718d8b0f7134523cd87e4dcdb7b..33bcbdb6fef488983438c6584e3cbb0a44febb1a 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -2311,11 +2311,14 @@ static inline void *netdev_priv(const struct net_device *dev) */ #define SET_NETDEV_DEVTYPE(net, devtype) ((net)->dev.type = (devtype)) -/* Default NAPI poll() weight - * Device drivers are strongly advised to not use bigger value - */ +/* Default NAPI poll() weight. Highly recommended. */ #define NAPI_POLL_WEIGHT 64 +/* Device drivers are strongly advised to not use bigger value, + * as this might cause latencies in stress conditions. + */ +#define NAPI_POLL_WEIGHT_MAX 256 + /** * netif_napi_add - initialize a NAPI context * @dev: network device diff --git a/net/core/dev.c b/net/core/dev.c index 4086d335978c1bf62bd3965bd2ea96a4ac06b13d..496713fb6075bd8e5e22725e7c817172858e1dd7 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6608,7 +6608,7 @@ void netif_napi_add(struct net_device *dev, struct napi_struct *napi, INIT_LIST_HEAD(&napi->rx_list); napi->rx_count = 0; napi->poll = poll; - if (weight > NAPI_POLL_WEIGHT) + if (weight > NAPI_POLL_WEIGHT_MAX) netdev_err_once(dev, "%s() called with weight %d\n", __func__, weight); napi->weight = weight;