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From: Olivier Matz <olivier.matz@6wind.com>
To: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
Cc: Jan Blunck <jblunck@infradead.org>,
	"Richardson, Bruce" <bruce.richardson@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [RFC 0/8] mbuf: structure reorganization
Date: Tue, 28 Feb 2017 10:23:59 +0100	[thread overview]
Message-ID: <20170228102359.5d601797@platinum> (raw)
In-Reply-To: <2601191342CEEE43887BDE71AB9772583F11E992@irsmsx105.ger.corp.intel.com>

Hi,

On Tue, 28 Feb 2017 09:05:07 +0000, "Ananyev, Konstantin"
<konstantin.ananyev@intel.com> wrote:
> Hi everyone,
> 
> > >
> > > In my opinion, if we have the room in the first cache line, we
> > > should put it there. The only argument I see against is "we may
> > > find something more important in the future, and we won't have
> > > room for it in the first cache line". I don't feel we should
> > > penalize today's use cases for hypothetic future use cases.
> > >
> > >
> > >  
> > >> 2. timestamp normalization point
> > >>      inside PMD RX vs somewhere later as user needs it (extra
> > >> function in dev_ops?).  
> > >
> > > This point could be changed. My initial proposition tries to
> > > provide a generic API for timestamp. Let me remind it here:
> > >
> > > a- the timestamp is in nanosecond
> > > b- the reference is always the same for a given path: if the
> > > timestamp is set in a PMD, all the packets for this PMD will have
> > > the same reference, but for 2 different PMDs (or a sw lib), the
> > > reference would not be the same.
> > >
> > > We may remove a-, and just have:
> > >  - the reference and the unit are always the same for a given
> > > path: if the timestamp is set in a PMD, all the packets for this
> > > PMD will have the same reference and unit, but for 2 different
> > > PMDs (or a sw lib), they would not be the same.
> > >
> > > In both cases, we would need a conversion code (maybe in a
> > > library) if the application wants to work with timestamps from
> > > several sources. The second solution removes the normalization
> > > code in the PMD when not needed, it is probably better.  
> > 
> > I agree.  
> 
> One question - does that mean that application would need to
> keep a track from what PMD each particular packet came to do the
> normalization? Konstantin

I'd say yes. It does not look very difficult to do, since the mbuf
contains the input port id.


> > > About having the timestamp in the packet data, I don't think it is
> > > a good solution for a generic API in DPDK. The timestamp is a
> > > metadata, it has to go in the mbuf metadata. The packet data
> > > should not be modified when the timestamp is enabled.  
> > 
> > Good NICs already do that based on the packet type (e.g. NTP/PTP
> > packets). 
> > >
> > > But this would not prevent to have driver-specific features to do
> > > that. In that case, the application will be aware that it is
> > > using this specific driver and that it will receive a timestamp
> > > in the packet data.
> > >
> > > To summarize, the generic API could be:
> > > - an ethdev API to enable the timestamp in a PMD for received
> > > packets
> > > - a mbuf flag "timestamp present"
> > > - a mbuf 64b field to store the timestamp value
> > >
> > > Additionally, a driver-specific API can be added for a given PMD.
> > > Example:
> > > - the generic timestamp ethdev is disabled (or not supported)
> > > - a driver-specific feature "put timestamp in packet" is enabled
> > > It would have no additional cost compared to what we have today,
> > > since the timestamp in mbuf is not read/written.
> > >  
> > 
> > Thanks for the writeup. This sounds like a reasonable approach to
> > me.
> > 
> > Do you still want to call the 64bit field "timestamp" or rename it
> > to something neutral and document that it is used together with the
> > mbuf flags?  

I think timestamp is a good name. In the current RFC patchset, we have
this comment:

	/** Valid if PKT_RX_TIMESTAMP is set. The unit is nanoseconds */
	uint64_t timestamp;

We could change it to something like:

	/** Valid if PKT_RX_TIMESTAMP is set. The unit and time
	 *  reference are not normalized but are always the same
	 *  for a given port.
	 */
	uint64_t timestamp;


Regards,
Olivier

  reply	other threads:[~2017-02-28  9:24 UTC|newest]

Thread overview: 155+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-24 15:19 Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 1/8] mbuf: make segment prefree function public Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 2/8] mbuf: make raw free " Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 3/8] mbuf: set mbuf fields while in pool Olivier Matz
2017-01-24 15:50   ` Bruce Richardson
2017-02-28 14:51     ` Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 4/8] net: don't touch mbuf next or nb segs on Rx Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 5/8] mbuf: make rearm data address naturally aligned Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 6/8] mbuf: use 2 bytes for port and nb segments Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 7/8] mbuf: move sequence number in second cache line Olivier Matz
2017-01-24 15:19 ` [dpdk-dev] [RFC 8/8] mbuf: add a timestamp field Olivier Matz
2017-01-24 15:59 ` [dpdk-dev] [RFC 0/8] mbuf: structure reorganization Bruce Richardson
2017-01-24 16:16   ` Olivier MATZ
2017-02-06 18:41 ` Ananyev, Konstantin
2017-02-09 16:20   ` Morten Brørup
2017-02-09 16:56     ` Ananyev, Konstantin
2017-02-16 13:48   ` Olivier Matz
2017-02-16 15:46     ` Bruce Richardson
2017-02-16 16:14       ` Olivier Matz
2017-02-21 14:20         ` Morten Brørup
2017-02-21 14:28           ` Bruce Richardson
2017-02-21 15:04           ` Olivier MATZ
2017-02-21 15:18             ` Bruce Richardson
2017-02-21 15:18             ` Morten Brørup
2017-02-19 19:04       ` Chilikin, Andrey
2017-02-21  9:53         ` Olivier MATZ
2017-02-16 17:26     ` Jan Blunck
2017-02-17 10:51       ` Olivier Matz
2017-02-17 12:49         ` Nélio Laranjeiro
2017-02-17 13:51           ` Jan Blunck
2017-02-18  5:48             ` Andrew Rybchenko
2017-02-17 13:38         ` Jan Blunck
2017-02-17 14:17           ` Olivier Matz
2017-02-17 18:42             ` Ananyev, Konstantin
2017-02-21  9:53               ` Olivier MATZ
2017-02-21 10:28                 ` Ananyev, Konstantin
2017-02-20  9:27             ` Jan Blunck
2017-02-21  9:54               ` Olivier MATZ
2017-02-21 16:12                 ` Jan Blunck
2017-02-21 16:38                   ` Bruce Richardson
2017-02-21 17:04                     ` Jan Blunck
2017-02-21 17:26                       ` Ananyev, Konstantin
2017-02-21 19:17                         ` Jan Blunck
2017-02-21 20:30                           ` Ananyev, Konstantin
2017-02-21 21:51                             ` Morten Brørup
2017-02-24 14:11                               ` Olivier Matz
2017-02-24 14:00                             ` Olivier Matz
2017-02-24 14:21                               ` Bruce Richardson
2017-02-28  8:55                               ` Jan Blunck
2017-02-28  9:05                                 ` Ananyev, Konstantin
2017-02-28  9:23                                   ` Olivier Matz [this message]
2017-02-28  9:33                                     ` Jan Blunck
2017-02-28 10:29                                     ` Ananyev, Konstantin
2017-02-28 10:50                                       ` Olivier Matz
2017-02-28 11:48                                         ` Ananyev, Konstantin
2017-02-28 12:28                                           ` Olivier Matz
2017-02-28 22:53                                             ` Ananyev, Konstantin
2017-03-02 16:46                                               ` Olivier Matz
2017-03-08 11:11                                                 ` Ananyev, Konstantin
2017-03-20  9:00                                                   ` Olivier Matz
2017-03-22 17:42                                                     ` Ananyev, Konstantin
2017-03-24  8:35                                                       ` Jerin Jacob
2017-03-24 13:35                                                         ` Olivier Matz
2017-02-28  9:25                                   ` Jan Blunck
2017-02-19 23:45     ` Ananyev, Konstantin
2017-02-21  9:22     ` Morten Brørup
2017-02-21  9:54       ` Olivier MATZ
2017-03-08  9:41 ` [dpdk-dev] [PATCH 0/9] " Olivier Matz
2017-03-08  9:41   ` [dpdk-dev] [PATCH 1/9] mbuf: make segment prefree function public Olivier Matz
2017-03-08  9:41   ` [dpdk-dev] [PATCH 2/9] mbuf: make raw free " Olivier Matz
2017-03-08  9:41   ` [dpdk-dev] [PATCH 3/9] mbuf: set mbuf fields while in pool Olivier Matz
2017-03-31 11:21     ` Bruce Richardson
2017-03-31 11:51       ` Ananyev, Konstantin
2017-03-08  9:41   ` [dpdk-dev] [PATCH 4/9] drivers/net: don't touch mbuf next or nb segs on Rx Olivier Matz
2017-03-08  9:41   ` [dpdk-dev] [PATCH 5/9] mbuf: make rearm data address naturally aligned Olivier Matz
2017-03-08  9:41   ` [dpdk-dev] [PATCH 6/9] mbuf: use 2 bytes for port and nb segments Olivier Matz
2017-03-08  9:41   ` [dpdk-dev] [PATCH 7/9] mbuf: move sequence number in second cache line Olivier Matz
2017-03-08  9:42   ` [dpdk-dev] [PATCH 8/9] mbuf: add a timestamp field Olivier Matz
2017-04-04 10:29     ` [dpdk-dev] [PATCH 0/2] reduce writes to mbuf in ixgbe vRX Konstantin Ananyev
2017-04-07 15:13       ` Ferruh Yigit
2017-04-07 15:44         ` Ferruh Yigit
2017-04-09 22:56           ` Ananyev, Konstantin
2017-04-04 10:29     ` [dpdk-dev] [PATCH 1/2] net/ixgbe: eliminate mbuf write on rearm Konstantin Ananyev
2017-04-10 15:59       ` [dpdk-dev] [PATCH v2 0/2] reduce writes to mbuf in ixgbe vRX Konstantin Ananyev
2017-04-10 16:17         ` Ferruh Yigit
2017-04-10 15:59       ` [dpdk-dev] [PATCH v2 1/2] net/ixgbe: eliminate mbuf write on rearm Konstantin Ananyev
2017-04-10 15:59       ` [dpdk-dev] [PATCH v2 2/2] net/ixgbe: remove option to disable offload flags Konstantin Ananyev
2017-04-04 10:29     ` [dpdk-dev] [PATCH " Konstantin Ananyev
2017-03-08  9:42   ` [dpdk-dev] [PATCH 9/9] mbuf: reorder VLAN tci and buffer len fields Olivier Matz
2017-03-29 15:56   ` [dpdk-dev] [PATCH 0/9] mbuf: structure reorganization Olivier Matz
2017-03-29 16:03     ` Morten Brørup
2017-03-29 20:09     ` Bruce Richardson
2017-03-30  9:31       ` Bruce Richardson
2017-03-30 12:02         ` Olivier Matz
2017-03-30 12:23           ` Bruce Richardson
2017-03-30 16:45             ` Ananyev, Konstantin
2017-03-30 16:47               ` Ananyev, Konstantin
2017-03-30 18:06                 ` Ananyev, Konstantin
2017-03-31  8:41                   ` Olivier Matz
2017-03-31  9:58                     ` Ananyev, Konstantin
2017-03-31  1:00                 ` Ananyev, Konstantin
2017-03-31  7:21                   ` Morten Brørup
2017-03-31  8:26                   ` Olivier Matz
2017-03-31  8:41                     ` Bruce Richardson
2017-03-31  8:59                       ` Olivier Matz
2017-03-31  9:18                         ` Ananyev, Konstantin
2017-03-31  9:36                           ` Olivier Matz
2017-04-03 16:15                           ` Thomas Monjalon
2017-04-04  7:58                             ` Olivier MATZ
2017-04-04  8:53                               ` Bruce Richardson
2017-03-31  9:23                         ` Bruce Richardson
2017-03-31 11:18     ` Nélio Laranjeiro
2017-03-30 14:54   ` Andrew Rybchenko
2017-03-30 15:12   ` Jerin Jacob
2017-04-04 16:27   ` [dpdk-dev] [PATCH v2 0/8] " Olivier Matz
2017-04-04 16:28     ` [dpdk-dev] [PATCH v2 1/8] mbuf: make segment prefree function public Olivier Matz
2017-04-04 16:28     ` [dpdk-dev] [PATCH v2 2/8] mbuf: make raw free " Olivier Matz
2017-04-04 16:28     ` [dpdk-dev] [PATCH v2 3/8] mbuf: set mbuf fields while in pool Olivier Matz
2017-04-04 16:28     ` [dpdk-dev] [PATCH v2 4/8] drivers/net: don't touch mbuf next or nb segs on Rx Olivier Matz
2017-04-04 16:28     ` [dpdk-dev] [PATCH v2 5/8] mbuf: make rearm data address naturally aligned Olivier Matz
2017-04-04 16:28     ` [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port and nb segments Olivier Matz
2017-04-06  5:45       ` Yuanhan Liu
2017-04-18 13:03         ` Olivier MATZ
2017-07-04  7:54           ` Wang, Zhihong
2017-07-10  8:00             ` Olivier Matz
2017-07-10  8:15               ` Morten Brørup
2017-07-11 13:25                 ` Wiles, Keith
2017-07-11 13:30                   ` Morten Brørup
2017-07-11 15:05                     ` Thomas Monjalon
2017-07-11 15:23                       ` [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port and nbsegments Morten Brørup
2017-07-11 16:48                         ` Wiles, Keith
2017-07-12  7:25                           ` Morten Brørup
2017-07-12  9:02                             ` Yang, Zhiyong
2017-07-12  9:50                               ` [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port andnbsegments Morten Brørup
2017-07-12 15:35                                 ` Stephen Hemminger
2017-07-12 15:57                                   ` Morten Brørup
2017-07-12 16:23                                     ` Thomas Monjalon
2017-07-12 18:20                                       ` Wiles, Keith
2017-07-21 15:03                                       ` Bruce Richardson
2017-07-12 15:34                             ` [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port and nbsegments Wiles, Keith
2017-07-11 13:34                 ` [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port and nb segments Wiles, Keith
2017-07-11 13:46                   ` Olivier MATZ
2017-04-04 16:28     ` [dpdk-dev] [PATCH v2 7/8] mbuf: move sequence number in second cache line Olivier Matz
2017-04-04 16:28     ` [dpdk-dev] [PATCH v2 8/8] mbuf: add a timestamp field Olivier Matz
2017-04-05  9:37     ` [dpdk-dev] [PATCH v2 0/8] mbuf: structure reorganization Thomas Monjalon
2017-04-05  9:46       ` Olivier MATZ
2017-04-05  9:48       ` Richardson, Bruce
2017-04-05 12:06       ` Ferruh Yigit
2017-04-14 13:10       ` Ferruh Yigit
2017-04-18 13:04         ` Olivier MATZ
2017-04-19  9:39           ` Thomas Monjalon
2017-04-19 12:28             ` Olivier MATZ
2017-04-19 12:56               ` Thomas Monjalon
2017-04-19 13:03                 ` Ferruh Yigit
2017-04-19 13:12                   ` Thomas Monjalon

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