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[2a01:cb0c:5:a600:3456:36f7:e65e:d1a0]) by smtp.gmail.com with ESMTPSA id c20sm1873796wrb.65.2020.07.07.08.23.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jul 2020 08:23:05 -0700 (PDT) Date: Tue, 7 Jul 2020 17:23:04 +0200 From: Olivier Matz To: Viacheslav Ovsiienko Cc: dev@dpdk.org, matan@mellanox.com, rasland@mellanox.com, bernard.iremonger@intel.com, thomas@mellanox.net Message-ID: <20200707152304.GL5869@platinum> References: <1591771085-24959-1-git-send-email-viacheslavo@mellanox.com> <1594133832-12785-1-git-send-email-viacheslavo@mellanox.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1594133832-12785-1-git-send-email-viacheslavo@mellanox.com> User-Agent: Mutt/1.10.1 (2018-07-13) Subject: Re: [dpdk-dev] [PATCH v4 1/2] mbuf: introduce accurate packet Tx scheduling X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Tue, Jul 07, 2020 at 02:57:11PM +0000, Viacheslav Ovsiienko wrote: > There is the requirement on some networks for precise traffic timing > management. The ability to send (and, generally speaking, receive) > the packets at the very precisely specified moment of time provides > the opportunity to support the connections with Time Division > Multiplexing using the contemporary general purpose NIC without involving > an auxiliary hardware. For example, the supporting of O-RAN Fronthaul > interface is one of the promising features for potentially usage of the > precise time management for the egress packets. > > The main objective of this RFC is to specify the way how applications > can provide the moment of time at what the packet transmission must be > started and to describe in preliminary the supporting this feature from > mlx5 PMD side. > > The new dynamic timestamp field is proposed, it provides some timing > information, the units and time references (initial phase) are not > explicitly defined but are maintained always the same for a given port. > Some devices allow to query rte_eth_read_clock() that will return > the current device timestamp. The dynamic timestamp flag tells whether > the field contains actual timestamp value. For the packets being sent > this value can be used by PMD to schedule packet sending. > > After PKT_RX_TIMESTAMP flag and fixed timestamp field deprecation > and obsoleting, these dynamic flag and field will be used to manage > the timestamps on receiving datapath as well. > > When PMD sees the "rte_dynfield_timestamp" set on the packet being sent > it tries to synchronize the time of packet appearing on the wire with > the specified packet timestamp. If the specified one is in the past it > should be ignored, if one is in the distant future it should be capped > with some reasonable value (in range of seconds). These specific cases > ("too late" and "distant future") can be optionally reported via > device xstats to assist applications to detect the time-related > problems. > > There is no any packet reordering according timestamps is supposed, > neither within packet burst, nor between packets, it is an entirely > application responsibility to generate packets and its timestamps > in desired order. The timestamps can be put only in the first packet > in the burst providing the entire burst scheduling. > > PMD reports the ability to synchronize packet sending on timestamp > with new offload flag: > > This is palliative and is going to be replaced with new eth_dev API > about reporting/managing the supported dynamic flags and its related > features. This API would break ABI compatibility and can't be introduced > at the moment, so is postponed to 20.11. > > For testing purposes it is proposed to update testpmd "txonly" > forwarding mode routine. With this update testpmd application generates > the packets and sets the dynamic timestamps according to specified time > pattern if it sees the "rte_dynfield_timestamp" is registered. > > The new testpmd command is proposed to configure sending pattern: > > set tx_times , > > - the delay between the packets within the burst > specified in the device clock units. The number > of packets in the burst is defined by txburst parameter > > - the delay between the bursts in the device clock units > > As the result the bursts of packet will be transmitted with specific > delays between the packets within the burst and specific delay between > the bursts. The rte_eth_get_clock is supposed to be engaged to get the > current device clock value and provide the reference for the timestamps. > > Signed-off-by: Viacheslav Ovsiienko > --- > v1->v4: > - dedicated dynamic Tx timestamp flag instead of shared with Rx > - Doxygen-style comment > - comments update > > --- > lib/librte_ethdev/rte_ethdev.c | 1 + > lib/librte_ethdev/rte_ethdev.h | 4 ++++ > lib/librte_mbuf/rte_mbuf_dyn.h | 31 +++++++++++++++++++++++++++++++ > 3 files changed, 36 insertions(+) > > diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c > index 8e10a6f..02157d5 100644 > --- a/lib/librte_ethdev/rte_ethdev.c > +++ b/lib/librte_ethdev/rte_ethdev.c > @@ -162,6 +162,7 @@ struct rte_eth_xstats_name_off { > RTE_TX_OFFLOAD_BIT2STR(UDP_TNL_TSO), > RTE_TX_OFFLOAD_BIT2STR(IP_TNL_TSO), > RTE_TX_OFFLOAD_BIT2STR(OUTER_UDP_CKSUM), > + RTE_TX_OFFLOAD_BIT2STR(SEND_ON_TIMESTAMP), > }; > > #undef RTE_TX_OFFLOAD_BIT2STR > diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h > index a49242b..6f6454c 100644 > --- a/lib/librte_ethdev/rte_ethdev.h > +++ b/lib/librte_ethdev/rte_ethdev.h > @@ -1178,6 +1178,10 @@ struct rte_eth_conf { > /** Device supports outer UDP checksum */ > #define DEV_TX_OFFLOAD_OUTER_UDP_CKSUM 0x00100000 > > +/** Device supports send on timestamp */ > +#define DEV_TX_OFFLOAD_SEND_ON_TIMESTAMP 0x00200000 > + > + > #define RTE_ETH_DEV_CAPA_RUNTIME_RX_QUEUE_SETUP 0x00000001 > /**< Device supports Rx queue setup after device started*/ > #define RTE_ETH_DEV_CAPA_RUNTIME_TX_QUEUE_SETUP 0x00000002 > diff --git a/lib/librte_mbuf/rte_mbuf_dyn.h b/lib/librte_mbuf/rte_mbuf_dyn.h > index 96c3631..7e9f7d2 100644 > --- a/lib/librte_mbuf/rte_mbuf_dyn.h > +++ b/lib/librte_mbuf/rte_mbuf_dyn.h > @@ -250,4 +250,35 @@ int rte_mbuf_dynflag_lookup(const char *name, > #define RTE_MBUF_DYNFIELD_METADATA_NAME "rte_flow_dynfield_metadata" > #define RTE_MBUF_DYNFLAG_METADATA_NAME "rte_flow_dynflag_metadata" > > +/** > + * The timestamp dynamic field provides some timing information, the > + * units and time references (initial phase) are not explicitly defined > + * but are maintained always the same for a given port. Some devices allow4 allow4 -> allow > + * to query rte_eth_read_clock() that will return the current device > + * timestamp. The dynamic Tx timestamp flag tells whether the field contains > + * actual timestamp value. For the packets being sent this value can be > + * used by PMD to schedule packet sending. > + * > + * After PKT_RX_TIMESTAMP flag and fixed timestamp field deprecation > + * and obsoleting, the dedicated Rx timestamp flag is supposed to be > + * introduced and the shared dynamic timestamp field will be used > + * to handle the timestamps on receiving datapath as well. > + */ > +#define RTE_MBUF_DYNFIELD_TIMESTAMP_NAME "rte_dynfield_timestamp" > + > +/** > + * When PMD sees the RTE_MBUF_DYNFLAG_TX_TIMESTAMP_NAME flag set on the > + * packet being sent it tries to synchronize the time of packet appearing > + * on the wire with the specified packet timestamp. If the specified one > + * is in the past it should be ignored, if one is in the distant future > + * it should be capped with some reasonable value (in range of seconds). > + * > + * There is no any packet reordering according to timestamps is supposed, > + * neither for packet within the burst, nor for the whole bursts, it is > + * an entirely application responsibility to generate packets and its > + * timestamps in desired order. The timestamps might be put only in > + * the first packet in the burst providing the entire burst scheduling. > + */ > +#define RTE_MBUF_DYNFLAG_TX_TIMESTAMP_NAME "rte_dynflag_tx_timestamp" > + Acked-by: Olivier Matz