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From: Slava Ovsiienko <viacheslavo@mellanox.com>
To: Harman Kalra <hkalra@marvell.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	Thomas Monjalon <thomas@monjalon.net>,
	Matan Azrad <matan@mellanox.com>,
	Raslan Darawsheh <rasland@mellanox.com>,
	Ori Kam <orika@mellanox.com>,
	"olivier.matz@6wind.com" <olivier.matz@6wind.com>,
	Shahaf Shuler <shahafs@mellanox.com>
Subject: Re: [dpdk-dev] [EXT] RE: [RFC] mbuf: accurate packet Tx scheduling
Date: Wed, 1 Jul 2020 15:46:04 +0000
Message-ID: <AM4PR05MB32658C68421679E4039D9DF8D26C0@AM4PR05MB3265.eurprd05.prod.outlook.com> (raw)
In-Reply-To: <20200617155756.GA190547@outlook.office365.com>

> -----Original Message-----
> From: Harman Kalra <hkalra@marvell.com>
> Sent: Wednesday, June 17, 2020 18:58
> To: Slava Ovsiienko <viacheslavo@mellanox.com>
> Cc: dev@dpdk.org; Thomas Monjalon <thomas@monjalon.net>; Matan
> Azrad <matan@mellanox.com>; Raslan Darawsheh
> <rasland@mellanox.com>; Ori Kam <orika@mellanox.com>;
> olivier.matz@6wind.com; Shahaf Shuler <shahafs@mellanox.com>
> Subject: Re: [EXT] RE: [dpdk-dev] [RFC] mbuf: accurate packet Tx scheduling
> 
> On Wed, Jun 10, 2020 at 03:16:12PM +0000, Slava Ovsiienko wrote:
> 
> > External Email
> >
> > ----------------------------------------------------------------------
Hi, Harman

Sorry for delay - missed your reply.

[..skip..]
> > Should we waste CPU cycles to wait the desired moment of time? Can we
> > guarantee stable interrupt latency if we choose to schedule on interrupts
> approach?
> >
> > This RFC splits the responsibility - application should prepare the
> > data and specify when it desires to send, the rest is on PMD.
> 
> I agree with the fact that we cannot guarantee the delay between tx burst
> call and data on wire, hence PMD should take care of it.
> Even if PMD is holding, it is wastage of CPU cycles or if we setup an alarm
> then also interrupt latency might be a concern to achieve precise timming. So
> how are you planning to address both of above issue in PMD.

It is promoted to HW. The special WAIT descriptor with timestamp
is pushed to the queue and hardware just waits for the appropriate moment.
It is exactly the task for PMD - convert the timestamp in hardware related
entities and perform requested operation on hardware. Thus we should not
wait on CPU in any way - loop/interrupts, etc. Let NIC do it for us.
 
> >
> > > >
> > > > 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.
> > >
> > > So what I am understanding here is "rte_dynfield_timestamp" will
> > > provide information about three parameters:
> > > - timestamp at which TX should start
> > > - intra packet gap
> > > - intra burst gap.
> > >
> > > If its about "intra packet gap" then PMD can take care, but if it is
> > > about intra burst gap, application can take care of it.
> >
> > Not sure - the intra-burst gap might be pretty small.
> > It is supposed to handle intra-burst in the same way - by specifying
> > the timestamps. Waiting is supposed to be implemented on tx_burst() retry.
> > Prepare the packets with timestamps, tx_burst - if not all packets are
> > sent - it means queue is waiting for the schedult, retry with the remaining
> packets.
> > As option - we can implement intra-burst wait basing rte_eth_read_clock().
> 
> Yeah, I think app can make use of rte_eth_read_clock() to implement intra-
> burst gap.
> But my actual doubt was, what all information will app provide as part of
> "rte_dynfield_timestamp" - one I understand will be timestamp at which
> packets should be sent out. What else? intra-packet gap ?
Intra-packet gap is just the parameter of testpmd to provide some
preliminary feature testing. If intra-gap is too small even hardware might
not support. In mlx5 we are going to support the scheduling with minimal
granularity 250 nanoseconds, so minimal gap supported is 250ns,
on 100Gbps line speed it means at least two 1500B packets.

With best regards, Slava

  reply	other threads:[~2020-07-01 15:46 UTC|newest]

Thread overview: 86+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-10  6:38 [dpdk-dev] " 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 [this message]
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   ` [dpdk-dev] [PATCH v6 1/2] mbuf: introduce accurate packet Tx scheduling Ferruh Yigit
2020-07-10 12:32     ` 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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