DPDK patches and discussions
 help / color / mirror / Atom feed
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: Fri, 24 Feb 2017 15:00:53 +0100	[thread overview]
Message-ID: <20170224150053.279e718d@platinum> (raw)
In-Reply-To: <2601191342CEEE43887BDE71AB9772583F11B633@irsmsx105.ger.corp.intel.com>

Hi,

On Tue, 21 Feb 2017 20:30:57 +0000, "Ananyev, Konstantin"
<konstantin.ananyev@intel.com> wrote:
> > -----Original Message-----
> > From: jblunck@gmail.com [mailto:jblunck@gmail.com] On Behalf Of Jan
> > Blunck Sent: Tuesday, February 21, 2017 7:18 PM
> > To: Ananyev, Konstantin <konstantin.ananyev@intel.com>
> > Cc: Richardson, Bruce <bruce.richardson@intel.com>; Olivier MATZ
> > <olivier.matz@6wind.com>; dev@dpdk.org Subject: Re: [dpdk-dev] [RFC
> > 0/8] mbuf: structure reorganization
> > 
> > On Tue, Feb 21, 2017 at 6:26 PM, Ananyev, Konstantin
> > <konstantin.ananyev@intel.com> wrote:  
> > > Hi Jan,
> > >  
> > >> -----Original Message-----
> > >> From: jblunck@gmail.com [mailto:jblunck@gmail.com] On Behalf Of
> > >> Jan Blunck Sent: Tuesday, February 21, 2017 5:05 PM
> > >> To: Richardson, Bruce <bruce.richardson@intel.com>
> > >> Cc: Olivier MATZ <olivier.matz@6wind.com>; Ananyev, Konstantin
> > >> <konstantin.ananyev@intel.com>; dev@dpdk.org Subject: Re:
> > >> [dpdk-dev] [RFC 0/8] mbuf: structure reorganization
> > >>
> > >> On Tue, Feb 21, 2017 at 5:38 PM, Bruce Richardson
> > >> <bruce.richardson@intel.com> wrote:  
> > >> > On Tue, Feb 21, 2017 at 05:12:12PM +0100, Jan Blunck wrote:  
> > >> >>
> > >> >> Access through PMD specific function pointers should be
> > >> >> relatively fast on access. Modern architecture optimize that
> > >> >> use case well enough.
> > >> >>  
> > >> > The cost of doing a function call per packet to access data
> > >> > starts to add up very, very fast. For the app, once the data
> > >> > is written to the mbuf, it should be in the L1 cache, giving
> > >> > very fast access to it in a few cycles. However, if a function
> > >> > call has to be made in order to do the read, that makes the
> > >> > read of that field many times more expensive. 
> > >>
> > >> Exactly. Right now the timestamp normalization is done before
> > >> writing to each mbuf. Timestamps are usually read at most
> > >> once ... if at all.  
> > >
> > > Well we don't know for sure right?
> > > Someone can argue that there are plenty of scenarios  when
> > > other fields might also never be used/updated (rss, vlan, etc).
> > >
> > > So, are you suggesting to do normalization later?
> > > If so, then what would be the benefit (data still need to be in
> > > mbuf)?  
> > 
> > Yes, postponing normalization prevents you from doing unnecessary
> > work upfront. AFAIK not all NICs store timestamp data OOB, e.g. in
> > CQ.  
> 
> Yes, postponing normalization might help a bit (though I don't think
> much) in terms of calculations performed inside PMD.
> But we still need 8B inside mbuf to store the timestamp value,
> either normalized or raw one.
> So to clarify where is the disagreement:
> 1. timestamp position:
>     mbufs 1-st cacheline vs 2-nd cacheline


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.


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.

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.



Olivier

  parent reply	other threads:[~2017-02-24 14:00 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 [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20170224150053.279e718d@platinum \
    --to=olivier.matz@6wind.com \
    --cc=bruce.richardson@intel.com \
    --cc=dev@dpdk.org \
    --cc=jblunck@infradead.org \
    --cc=konstantin.ananyev@intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).