From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?= Date: Tue, 8 Sep 2020 13:49:54 +0200 Subject: [Intel-wired-lan] [PATCH bpf-next 4/4] ixgbe, xsk: use XSK_NAPI_WEIGHT as NAPI poll budget In-Reply-To: <6bbf1793-d2be-b724-eec4-65546d4cbc9c@gmail.com> References: <20200907150217.30888-1-bjorn.topel@gmail.com> <20200907150217.30888-5-bjorn.topel@gmail.com> <6bbf1793-d2be-b724-eec4-65546d4cbc9c@gmail.com> Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: intel-wired-lan@osuosl.org List-ID: On 2020-09-08 11:45, Eric Dumazet wrote: > > > On 9/7/20 5:02 PM, Bj?rn T?pel wrote: >> From: Bj?rn T?pel >> >> Start using XSK_NAPI_WEIGHT as NAPI poll budget for the AF_XDP Rx >> zero-copy path. >> >> Signed-off-by: Bj?rn T?pel >> --- >> 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. > Thanks for having a look, Eric! By diverging from best practices, do you mean that multiple queues share one NAPI context, and the budget is split over the queues (say, 4 queues, 64/4 per queue), or that Tx simply ignores the budget? Or both? > 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. > Hmm, so a configurable NAPI budget for, say, the AF_XDP enabled queues/NAPIs? Am I reading that correct? (Note that this is *only* for the AF_XDP enabled queues.) I'll try to rework this to something more palatable. Thanks, Bj?rn > 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; >