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From: Olivier Matz <olivier.matz@6wind.com>
To: Jan Blunck <jblunck@infradead.org>
Cc: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [RFC 0/8] mbuf: structure reorganization
Date: Fri, 17 Feb 2017 11:51:53 +0100	[thread overview]
Message-ID: <20170217115153.0afeb061@platinum> (raw)
In-Reply-To: <CALe+Z00Y_=4rsAjTeyaEzKFqtuMb6HMRUEUDL2LveJx6bWL-dA@mail.gmail.com>

Hi Jan,

On Thu, 16 Feb 2017 18:26:39 +0100, Jan Blunck <jblunck@infradead.org>
wrote:
> On Thu, Feb 16, 2017 at 2:48 PM, Olivier Matz
> <olivier.matz@6wind.com> wrote:
> > On Mon, 6 Feb 2017 18:41:27 +0000, "Ananyev, Konstantin"
> > <konstantin.ananyev@intel.com> wrote:  
> >> >
> >> > The main changes are:
> >> > - reorder structure to increase vector performance on some non-ia
> >> >   platforms.
> >> > - add a 64bits timestamp field in the 1st cache line  
> >>
> >> Wonder why it deserves to be in first cache line?
> >> How it differs from seqn below (pure SW stuff right now).  
> >
> > In case the timestamp is set from a NIC value, it is set in the Rx
> > path. So that's why I think it deserve to be located in the 1st
> > cache line.
> >
> > As you said, the seqn is a pure sw stuff right: it is set in a lib,
> > not in a PMD rx path.
> >  
> 
> If we talk about setting the timestamp value in the RX path this
> implicitly means software timestamps. Hardware timestamping usually
> works by letting the hardware inject sync events for coarse time
> tracking and additionally injecting fine granular per-packet ticks at
> a specific offset in the packet. Out of performance reasons I don't
> think it makes sense to extract this during the burst and write it
> into the mbuf again.

From what I've understand, at least it does not work like this for
mellanox NICs: timestamp is a metadata attached to a rx packet. But
maybe they (and other NIC vendors interrested in the feature) can
confirm or not.

> 
> The problem with timestamps is to get the abstraction right wrt the
> correction factors and the size of the tick vs. the timestamp in the
> events injected. From my perspective it would be better to extract the
> handling of timestamp data into a library with PMD specific
> implementation of the conversions. That way the normalized timestamp
> values can get extracted if they are present. The mbuf itself would
> only indicate the presence of timestamp metadata in that case.

I agree however that we need to properly define the meaning of this
field. My idea is:

- the timestamp is in nanosecond
- 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.

I think it's enough for many use cases.
We can later add helpers to compare timestamps with different
references.


Regards,
Olivier

  reply	other threads:[~2017-02-17 10:51 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 [this message]
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
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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