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From: Ferruh Yigit <ferruh.yigit@intel.com>
To: Viacheslav Ovsiienko <viacheslavo@mellanox.com>, dev@dpdk.org
Cc: matan@mellanox.com, rasland@mellanox.com, olivier.matz@6wind.com,
	bernard.iremonger@intel.com, thomas@monjalon.com,
	Andrew Rybchenko <arybchenko@solarflare.com>
Subject: Re: [dpdk-dev] [PATCH v6 1/2] mbuf: introduce accurate packet Tx scheduling
Date: Fri, 10 Jul 2020 00:47:29 +0100
Message-ID: <c96bb381-abef-3c93-9091-07ada342fc7d@intel.com> (raw)
In-Reply-To: <1594298216-3746-1-git-send-email-viacheslavo@mellanox.com>

On 7/9/2020 1:36 PM, 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.

Is this a HW support, or is the scheduling planned to be done in the driver?

> 
> The main objective of this RFC is to specify the way how applications

It is no more RFC.

> 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.

I was about the ask this, will there be a PMD counterpart implementation of the
feature? It would be better to have it as part of this set.
What is the plan for the PMD implementation?

> 
> 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.
> 
> The device clock is opaque entity, the units and frequency are
> vendor specific and might depend on hardware capabilities and
> configurations. If might (or not) be synchronized with real time
> via PTP, might (or not) be synchronous with CPU clock (for example
> if NIC and CPU share the same clock source there might be no
> any drift between the NIC and CPU clocks), etc.
> 
> 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. Having the dedicated
> flags for Rx/Tx timestamps allows applications not to perform explicit
> flags reset on forwarding and not to promote received timestamps
> to the transmitting datapath by default. The static PKT_RX_TIMESTAMP
> is considered as candidate to become the dynamic flag.

Is there a deprecation notice for 'PKT_RX_TIMESTAMP'? Is this decided?

> 
> 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.

Good to hear that there will be a generic API to get supported dynamic flags. I
was concerned about adding 'DEV_TX_OFFLOAD_SEND_ON_TIMESTAMP' flag, since not
sure if there will be any other PMD that will want to use it.
The trouble is it is hard to remove a public macro after it is introduced, in
this release I think only single PMD (mlx) will support this feature, and in
next release the plan is to remove the macro. In this case what do you think to
not introduce the flag at all?

> 
> 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 <burst_gap>,<intra_gap>
> 
> <intra_gap> - 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
> 
> <burst_gap> - 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

'rte_eth_read_clock()'?

> current device clock value and provide the reference for the timestamps.
> 
> Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
> Acked-by: Olivier Matz <olivier.matz@6wind.com>
> 
> ---
>   v1->v4:
>      - dedicated dynamic Tx timestamp flag instead of shared with Rx
>   v4->v5:
>      - elaborated commit message
>      - more words about device clocks added,
>      - note about dedicated Rx/Tx timestamp flags added
>   v5->v6:
>      - release notes are updated
> ---
>  doc/guides/rel_notes/release_20_08.rst |  6 ++++++
>  lib/librte_ethdev/rte_ethdev.c         |  1 +
>  lib/librte_ethdev/rte_ethdev.h         |  4 ++++
>  lib/librte_mbuf/rte_mbuf_dyn.h         | 31 +++++++++++++++++++++++++++++++
>  4 files changed, 42 insertions(+)
> 
> diff --git a/doc/guides/rel_notes/release_20_08.rst b/doc/guides/rel_notes/release_20_08.rst
> index 988474c..5527bab 100644
> --- a/doc/guides/rel_notes/release_20_08.rst
> +++ b/doc/guides/rel_notes/release_20_08.rst
> @@ -200,6 +200,12 @@ New Features
>    See the :doc:`../sample_app_ug/l2_forward_real_virtual` for more
>    details of this parameter usage.
>  
> +* **Introduced send packet scheduling on the timestamps.**
> +
> +  Added the new mbuf dynamic field and flag to provide timestamp on what packet
> +  transmitting can be synchronized. The device Tx offload flag is added to
> +  indicate the PMD supports send scheduling.
> +

This is a core library change, can go up in the section, please check the
section comment for the ordering details.

>  
>  Removed Items
>  -------------
> diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
> index 7022bd7..c48ca2a 100644
> --- a/lib/librte_ethdev/rte_ethdev.c
> +++ b/lib/librte_ethdev/rte_ethdev.c
> @@ -160,6 +160,7 @@ 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 631b146..97313a0 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

Please cc the ethdev maintainers.

As mentioned above my concern is if this is generic enough or are we adding a
flag to a specific PMD? And since commit log says this is temporary solution for
just this release, I repeat my question if we can remove the flag completely?


  parent reply	other threads:[~2020-07-09 23:47 UTC|newest]

Thread overview: 86+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-10  6:38 [dpdk-dev] [RFC] mbuf: " Viacheslav Ovsiienko
2020-06-10 13:33 ` Harman Kalra
2020-06-10 15:16   ` Slava Ovsiienko
2020-06-17 15:57     ` [dpdk-dev] [EXT] " Harman Kalra
2020-07-01 15:46       ` Slava Ovsiienko
2020-07-01 15:36 ` [dpdk-dev] [PATCH 1/2] mbuf: introduce " Viacheslav Ovsiienko
2020-07-01 15:36   ` [dpdk-dev] [PATCH 2/2] app/testpmd: add send scheduling test capability Viacheslav Ovsiienko
2020-07-07 11:50   ` [dpdk-dev] [PATCH 1/2] mbuf: introduce accurate packet Tx scheduling Olivier Matz
2020-07-07 12:46     ` Slava Ovsiienko
2020-07-07 12:59 ` [dpdk-dev] [PATCH v2 " Viacheslav Ovsiienko
2020-07-07 12:59   ` [dpdk-dev] [PATCH v2 2/2] app/testpmd: add send scheduling test capability Viacheslav Ovsiienko
2020-07-07 13:08 ` [dpdk-dev] [PATCH v3 1/2] mbuf: introduce accurate packet Tx scheduling Viacheslav Ovsiienko
2020-07-07 13:08   ` [dpdk-dev] [PATCH v3 2/2] app/testpmd: add send scheduling test capability Viacheslav Ovsiienko
2020-07-07 14:32   ` [dpdk-dev] [PATCH v3 1/2] mbuf: introduce accurate packet Tx scheduling Olivier Matz
2020-07-07 14:57 ` [dpdk-dev] [PATCH v4 " Viacheslav Ovsiienko
2020-07-07 14:57   ` [dpdk-dev] [PATCH v4 2/2] app/testpmd: add send scheduling test capability Viacheslav Ovsiienko
2020-07-07 15:23   ` [dpdk-dev] [PATCH v4 1/2] mbuf: introduce accurate packet Tx scheduling Olivier Matz
2020-07-08 14:16   ` [dpdk-dev] [PATCH v4 1/2] mbuf: introduce accurate packet Txscheduling Morten Brørup
2020-07-08 14:54     ` Slava Ovsiienko
2020-07-08 15:27       ` Morten Brørup
2020-07-08 15:51         ` Slava Ovsiienko
2020-07-08 15:47 ` [dpdk-dev] [PATCH v5 1/2] mbuf: introduce accurate packet Tx scheduling Viacheslav Ovsiienko
2020-07-08 15:47   ` [dpdk-dev] [PATCH v5 2/2] app/testpmd: add send scheduling test capability Viacheslav Ovsiienko
2020-07-08 16:05   ` [dpdk-dev] [PATCH v5 1/2] mbuf: introduce accurate packet Tx scheduling Slava Ovsiienko
2020-07-09 12:26   ` Thomas Monjalon
2020-07-09 12:36 ` [dpdk-dev] [PATCH v6 " Viacheslav Ovsiienko
2020-07-09 12:36   ` [dpdk-dev] [PATCH v6 2/2] app/testpmd: add send scheduling test capability Viacheslav Ovsiienko
2020-07-09 23:58     ` Ferruh Yigit
2020-07-10 12:41       ` Slava Ovsiienko
2020-07-09 23:47   ` Ferruh Yigit [this message]
2020-07-10 12:32     ` [dpdk-dev] [PATCH v6 1/2] mbuf: introduce accurate packet Tx scheduling Slava Ovsiienko
2020-07-10 12:39 ` [dpdk-dev] [PATCH v7 " Viacheslav Ovsiienko
2020-07-10 12:39   ` [dpdk-dev] [PATCH v7 2/2] app/testpmd: add send scheduling test capability Viacheslav Ovsiienko
2020-07-10 15:46   ` [dpdk-dev] [PATCH v7 1/2] mbuf: introduce accurate packet Tx scheduling Slava Ovsiienko
2020-07-10 22:07     ` Ferruh Yigit
2020-07-15  6:21 ` [dpdk-dev] [PATCH v2 00/17] net/mlx5: " Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 01/17] common/mlx5: update common part to support packet pacing Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 02/17] net/mlx5: introduce send scheduling devargs Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 03/17] net/mlx5: fix UAR lock sharing for multiport devices Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 04/17] net/mlx5: introduce shared UAR resource Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 05/17] net/mlx5: create clock queue for packet pacing Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 06/17] net/mlx5: create rearm " Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 07/17] net/mlx5: create Tx queues with DevX Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 08/17] net/mlx5: allocate packet pacing context Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 09/17] net/mlx5: introduce clock queue service routine Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 10/17] net/mlx5: prepare Tx queue structures to support timestamp Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 11/17] net/mlx5: convert timestamp to completion index Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 12/17] net/mlx5: prepare Tx datapath to support sheduling Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 13/17] net/mlx5: add scheduling support to send routine template Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 14/17] net/mlx5: add read device clock support Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 15/17] net/mlx5: provide the send scheduling error statistics Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 16/17] common/mlx5: add register access DevX routine Viacheslav Ovsiienko
2020-07-15  6:21   ` [dpdk-dev] [PATCH v2 17/17] net/mlx5: convert Rx timestamps in realtime format Viacheslav Ovsiienko
2020-07-16  8:23 ` [dpdk-dev] [PATCH v3 00/17] net/mlx5: introduce accurate packet Tx scheduling Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 01/17] common/mlx5: update common part to support packet pacing Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 02/17] net/mlx5: introduce send scheduling devargs Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 03/17] net/mlx5: fix UAR lock sharing for multiport devices Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 04/17] net/mlx5: introduce shared UAR resource Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 05/17] net/mlx5: create clock queue for packet pacing Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 06/17] net/mlx5: create rearm " Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 07/17] net/mlx5: create Tx queues with DevX Viacheslav Ovsiienko
2020-07-20 14:18     ` Ferruh Yigit
2020-07-20 15:25       ` Ferruh Yigit
2020-07-21 11:35         ` Slava Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 08/17] net/mlx5: allocate packet pacing context Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 09/17] net/mlx5: introduce clock queue service routine Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 10/17] net/mlx5: prepare Tx queue structures to support timestamp Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 11/17] net/mlx5: convert timestamp to completion index Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 12/17] net/mlx5: prepare Tx datapath to support sheduling Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 13/17] net/mlx5: add scheduling support to send routine template Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 14/17] net/mlx5: add read device clock support Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 15/17] net/mlx5: provide the send scheduling error statistics Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 16/17] common/mlx5: add register access DevX routine Viacheslav Ovsiienko
2020-07-16  8:23   ` [dpdk-dev] [PATCH v3 17/17] net/mlx5: convert Rx timestamps in realtime format Viacheslav Ovsiienko
2020-07-16 20:20   ` [dpdk-dev] [PATCH v3 00/17] net/mlx5: introduce accurate packet Tx scheduling Raslan Darawsheh
2020-07-17 14:28 ` [dpdk-dev] [PATCH 1/3] net/mlx5: fix compilation issue with missing DevX event Viacheslav Ovsiienko
2020-07-17 14:28   ` [dpdk-dev] [PATCH 2/3] net/mlx5: fix compilation issue with atomic128 exchange Viacheslav Ovsiienko
2020-07-17 15:08     ` Thomas Monjalon
2020-07-17 15:15       ` Slava Ovsiienko
2020-07-17 14:28   ` [dpdk-dev] [PATCH 3/3] common/mlx5: fix DevX register access opcode Viacheslav Ovsiienko
2020-07-17 15:05     ` Thomas Monjalon
2020-07-17 15:11       ` Slava Ovsiienko
2020-07-17 15:19         ` Thomas Monjalon
2020-07-17 15:23           ` Slava Ovsiienko
2020-07-17 15:59             ` Thomas Monjalon
2020-07-18 13:38   ` [dpdk-dev] [PATCH 1/3] net/mlx5: fix compilation issue with missing DevX event Raslan Darawsheh

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