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From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: "Morten Brørup" <mb@smartsharesystems.com>,
	"Yigit, Ferruh" <ferruh.yigit@intel.com>,
	"Thomas Monjalon" <thomas@monjalon.net>,
	"Richardson, Bruce" <bruce.richardson@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	"olivier.matz@6wind.com" <olivier.matz@6wind.com>,
	"andrew.rybchenko@oktetlabs.ru" <andrew.rybchenko@oktetlabs.ru>,
	"honnappa.nagarahalli@arm.com" <honnappa.nagarahalli@arm.com>,
	"jerinj@marvell.com" <jerinj@marvell.com>,
	"gakhil@marvell.com" <gakhil@marvell.com>
Subject: Re: [dpdk-dev] [PATCH] parray: introduce internal API for dynamic arrays
Date: Tue, 22 Jun 2021 08:33:48 +0000	[thread overview]
Message-ID: <DM6PR11MB4491D4F6FAFDD6E8EEC2A78F9A099@DM6PR11MB4491.namprd11.prod.outlook.com> (raw)
In-Reply-To: <98CBD80474FA8B44BF855DF32C47DC35C6187B@smartserver.smartshare.dk>

> 
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Ananyev,
> > Konstantin
> >
> > >
> > > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Ananyev,
> > > > Konstantin
> > > >
> > > > > > How can we hide the callbacks since they are used by inline
> > burst
> > > > functions.
> > > > >
> > > > > I probably I owe a better explanation to what I meant in first
> > mail.
> > > > > Otherwise it sounds confusing.
> > > > > I'll try to write a more detailed one in next few days.
> > > >
> > > > Actually I gave it another thought over weekend, and might be we
> > can
> > > > hide rte_eth_dev_cb even in a simpler way. I'd use eth_rx_burst()
> > as
> > > > an example, but the same principle applies to other 'fast'
> > functions.
> > > >
> > > >  1. Needed changes for PMDs rx_pkt_burst():
> > > >     a) change function prototype to accept 'uint16_t port_id' and
> > > > 'uint16_t queue_id',
> > > >          instead of current 'void *'.
> > > >     b) Each PMD rx_pkt_burst() will have to call
> > rte_eth_rx_epilog()
> > > > function at return.
> > > >          This  inline function will do all CB calls for that queue.
> > > >
> > > > To be more specific, let say we have some PMD: xyz with RX
> > function:
> > > >
> > > > uint16_t
> > > > xyz_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t
> > > > nb_pkts)
> > > > {
> > > >      struct xyz_rx_queue *rxq = rx_queue;
> > > >      uint16_t nb_rx = 0;
> > > >
> > > >      /* do actual stuff here */
> > > >     ....
> > > >     return nb_rx;
> > > > }
> > > >
> > > > It will be transformed to:
> > > >
> > > > uint16_t
> > > > xyz_recv_pkts(uint16_t port_id, uint16_t queue_id, struct rte_mbuf
> > > > **rx_pkts, uint16_t nb_pkts)
> > > > {
> > > >          struct xyz_rx_queue *rxq;
> > > >          uint16_t nb_rx;
> > > >
> > > >          rxq = _rte_eth_rx_prolog(port_id, queue_id);
> > > >          if (rxq == NULL)
> > > >              return 0;
> > > >          nb_rx = _xyz_real_recv_pkts(rxq, rx_pkts, nb_pkts);
> > > >          return _rte_eth_rx_epilog(port_id, queue_id, rx_pkts,
> > > > nb_pkts);
> > > > }
> > > >
> > > > And somewhere in ethdev_private.h:
> > > >
> > > > static inline void *
> > > > _rte_eth_rx_prolog(uint16_t port_id, uint16_t queue_id);
> > > > {
> > > >    struct rte_eth_dev *dev = &rte_eth_devices[port_id];
> > > >
> > > > #ifdef RTE_ETHDEV_DEBUG_RX
> > > >         RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, NULL);
> > > >         RTE_FUNC_PTR_OR_ERR_RET(*dev->rx_pkt_burst, NULL);
> > > >
> > > >         if (queue_id >= dev->data->nb_rx_queues) {
> > > >                 RTE_ETHDEV_LOG(ERR, "Invalid RX queue_id=%u\n",
> > > > queue_id);
> > > >                 return NULL;
> > > >         }
> > > > #endif
> > > >   return dev->data->rx_queues[queue_id];
> > > > }
> > > >
> > > > static inline uint16_t
> > > > _rte_eth_rx_epilog(uint16_t port_id, uint16_t queue_id, struct
> > rte_mbuf
> > > > **rx_pkts, const uint16_t nb_pkts);
> > > > {
> > > >     struct rte_eth_dev *dev = &rte_eth_devices[port_id];
> > > >
> > > > #ifdef RTE_ETHDEV_RXTX_CALLBACKS
> > > >         struct rte_eth_rxtx_callback *cb;
> > > >
> > > >         /* __ATOMIC_RELEASE memory order was used when the
> > > >          * call back was inserted into the list.
> > > >          * Since there is a clear dependency between loading
> > > >          * cb and cb->fn/cb->next, __ATOMIC_ACQUIRE memory order is
> > > >          * not required.
> > > >          */
> > > >         cb = __atomic_load_n(&dev->post_rx_burst_cbs[queue_id],
> > > >                                 __ATOMIC_RELAXED);
> > > >
> > > >         if (unlikely(cb != NULL)) {
> > > >                 do {
> > > >                         nb_rx = cb->fn.rx(port_id, queue_id,
> > rx_pkts,
> > > > nb_rx,
> > > >                                                 nb_pkts, cb-
> > >param);
> > > >                         cb = cb->next;
> > > >                 } while (cb != NULL);
> > > >         }
> > > > #endif
> > > >
> > > >         rte_ethdev_trace_rx_burst(port_id, queue_id, (void
> > **)rx_pkts,
> > > > nb_rx);
> > > >         return nb_rx;
> > > >  }
> > >
> > > That would make the compiler inline _rte_eth_rx_epilog() into the
> > driver when compiling the DPDK library. But
> > > RTE_ETHDEV_RXTX_CALLBACKS is a definition for the application
> > developer to use when compiling the DPDK application.
> >
> > I believe it is for both - user app and DPDK drivers.
> > AFAIK, they both have to use the same rte_config.h, otherwise things
> > will be broken.
> > If let say RTE_ETHDEV_RXTX_CALLBACKS is not enabled in ethdev, then
> > user wouldn't be able to add a callback at first place.
> 
> In the case of RTE_ETHDEV_RXTX_CALLBACKS, it is independent:

Not really.
There are few libraries within DPDK that do rely on rx/tx callbacks:
bpf, latencystat, pdump, power.
With the approach above their functionality will be broken -
setup functions will return success, but actual callbacks will not be invoked. 
From other side, some libraries do invoke rx/tx burst on their own: ip-pipeline, graph.
For them callback invocation will continue to work, even when
RTE_ETHDEV_RXTX_CALLBACKS is disabled in the app.
In general, building DPDK libs and user app with different rte_config.h is really a bad idea.
It might work in some cases, but I believe it is not supported and user should not rely on it.
If user needs to disable RTE_ETHDEV_RXTX_CALLBACKS in his app, then the proper way would be:
- update rte_config.h
- rebuild both DPDK and the app with new config

> 
> If it is not compiled with the DPDK library, attempts to install callbacks from the application will fail with ENOTSUP.
> 
> If it is not compiled with the DPDK application, no time will be spent trying to determine if any there are any callbacks to call.
> 
> > BTW,  such change will allow us to make RTE_ETHDEV_RXTX_CALLBACKS
> > internal for ethdev/PMD layer, which is a good thing from my
> > perspective.
> 
> If it can be done without degrading performance for applications not using callbacks.


  reply	other threads:[~2021-06-22  8:34 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-14 10:58 Thomas Monjalon
2021-06-14 12:22 ` Morten Brørup
2021-06-14 13:15   ` Bruce Richardson
2021-06-14 13:32     ` Thomas Monjalon
2021-06-14 14:59       ` Ananyev, Konstantin
2021-06-14 15:48         ` Jerin Jacob
2021-06-15  6:52           ` Thomas Monjalon
2021-06-15  8:00             ` Jerin Jacob
2021-06-15  9:18               ` Thomas Monjalon
2021-06-15  9:33             ` Ananyev, Konstantin
2021-06-15  9:50               ` Thomas Monjalon
2021-06-15 10:08                 ` Ananyev, Konstantin
2021-06-15 14:02                   ` Thomas Monjalon
2021-06-15 14:37                     ` Honnappa Nagarahalli
2021-06-14 15:54         ` Ananyev, Konstantin
2021-06-17 13:08           ` Ferruh Yigit
2021-06-17 14:58             ` Ananyev, Konstantin
2021-06-17 15:17               ` Morten Brørup
2021-06-17 16:12                 ` Ferruh Yigit
2021-06-17 16:55                   ` Morten Brørup
2021-06-18 10:21                     ` Ferruh Yigit
2021-06-17 17:05                   ` Ananyev, Konstantin
2021-06-18  9:14                     ` Morten Brørup
2021-06-18 10:47                       ` Ferruh Yigit
2021-06-18 11:16                         ` Morten Brørup
2021-06-18 10:28                     ` Ferruh Yigit
2021-06-17 15:44               ` Ferruh Yigit
2021-06-18 10:41                 ` Ananyev, Konstantin
2021-06-18 10:49                   ` Ferruh Yigit
2021-06-21 11:06                   ` Ananyev, Konstantin
2021-06-21 12:10                     ` Morten Brørup
2021-06-21 12:30                       ` Ananyev, Konstantin
2021-06-21 13:28                         ` Morten Brørup
     [not found]                           ` <DM6PR11MB4491D4F6FAFDD6E8EEC2A78F9A099@DM6PR11MB4491.namprd11.prod.outlook .com>
2021-06-22  8:33                           ` Ananyev, Konstantin [this message]
2021-06-22 10:01                             ` Morten Brørup
2021-06-22 12:13                               ` Ananyev, Konstantin
2021-06-22 13:18                                 ` Morten Brørup
2021-06-21 14:10                         ` Ferruh Yigit
2021-06-21 14:38                           ` Ananyev, Konstantin
2021-06-21 15:56                             ` Ferruh Yigit
2021-06-21 18:17                               ` Ananyev, Konstantin
2021-06-21 14:05                     ` Ferruh Yigit
2021-06-21 14:42                       ` Ananyev, Konstantin
2021-06-21 15:32                         ` Ferruh Yigit
2021-06-21 15:37                           ` Ananyev, Konstantin
2021-06-14 15:48       ` Morten Brørup
2021-06-15  6:48         ` Thomas Monjalon
2021-06-15  7:53           ` Morten Brørup
2021-06-15  8:44             ` Bruce Richardson
2021-06-15  9:28               ` Thomas Monjalon
2021-06-16  9:42           ` Jerin Jacob
2021-06-16 11:27             ` Morten Brørup
2021-06-16 12:00               ` Jerin Jacob
2021-06-16 13:02               ` Bruce Richardson
2021-06-16 15:01                 ` Morten Brørup
2021-06-16 17:40                   ` Bruce Richardson
2021-06-16 12:22             ` Burakov, Anatoly
2021-06-16 12:59               ` Jerin Jacob
2021-06-16 22:58                 ` Dmitry Kozlyuk
2021-06-14 13:28   ` Thomas Monjalon
2021-06-16 11:11 ` Burakov, Anatoly

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