From: Tom Barbette <barbette@kth.se>
To: Ferruh Yigit <ferruh.yigit@intel.com>,
Shahaf Shuler <shahafs@mellanox.com>,
"dev@dpdk.org" <dev@dpdk.org>
Cc: "bruce.richardson@intel.com" <bruce.richardson@intel.com>,
"john.mcnamara@intel.com" <john.mcnamara@intel.com>,
Thomas Monjalon <thomas@monjalon.net>,
Andrew Rybchenko <arybchenko@solarflare.com>,
Yongseok Koh <yskoh@mellanox.com>,
Alejandro Lucero <alejandro.lucero@netronome.com>,
Konstantin Ananyev <konstantin.ananyev@intel.com>
Subject: Re: [dpdk-dev] [PATCH 1/3] rte_ethdev: Add API function to read dev clock
Date: Tue, 8 Jan 2019 11:30:39 +0000 [thread overview]
Message-ID: <1546947039501.61612@kth.se> (raw)
In-Reply-To: <e1828c02-e739-8045-0698-562692d12b4d@intel.com>
Ferruh Yigit wrote:
> Why timestamp offloading become useless? When timestamp offloading enabled,
> device fills 'mbuf.timestamp' and you can use it.
But the frequency is unknown, and the reference time neither. So it can be used only to know that "some time passed" between packets.
> For your case this timestamp for mlx is device clock and you are adding this API
> to be able to convert device clock to real time, this is not something enables
> the timestamp offload.
I get your point, but a keyboard is highly required to use a computer. It's pretty much useless without it. Without this API, the timestamp offload makes no sense. It's a random number generator at best...
> Technically driver can set the 'mbuf.timestamp' with the real clock right, if it
> is required? Or this can be defined by a devarg?
I don't think so. Device have no sense of system time. And doing it in the driver is tricky because it depends on the user needs. Catch-up with NTP updates would need a timer and various parameters... Hence we prefer to give a simple working code, and users may do this if they want.
For the other comments it's not my call... I would just underline that timestamp offload is not usable in the current state, and there is a lot of use case for monitoring latency-sensitive applications.
Tom
next prev parent reply other threads:[~2019-01-08 11:30 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-21 8:25 Tom Barbette
2018-12-23 6:06 ` Shahaf Shuler
2019-01-02 17:44 ` Ferruh Yigit
2019-01-08 11:30 ` Tom Barbette [this message]
2019-03-19 13:32 ` Yigit, Ferruh
2019-03-19 13:32 ` Yigit, Ferruh
2019-03-20 14:48 ` Thomas Monjalon
2019-03-20 14:48 ` Thomas Monjalon
2019-03-20 15:57 ` Andrew Rybchenko
2019-03-20 15:57 ` Andrew Rybchenko
2019-03-21 19:37 ` Ferruh Yigit
2019-03-21 19:37 ` Ferruh Yigit
-- strict thread matches above, loose matches on Subject: below --
2018-12-19 13:49 [dpdk-dev] [PATCH 0/3] Add rte_eth_read_clock API Tom Barbette
2018-12-19 13:49 ` [dpdk-dev] [PATCH 1/3] rte_ethdev: Add API function to read dev clock Tom Barbette
2018-12-20 6:42 ` Shahaf Shuler
2018-12-20 19:55 ` Ferruh Yigit
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=1546947039501.61612@kth.se \
--to=barbette@kth.se \
--cc=alejandro.lucero@netronome.com \
--cc=arybchenko@solarflare.com \
--cc=bruce.richardson@intel.com \
--cc=dev@dpdk.org \
--cc=ferruh.yigit@intel.com \
--cc=john.mcnamara@intel.com \
--cc=konstantin.ananyev@intel.com \
--cc=shahafs@mellanox.com \
--cc=thomas@monjalon.net \
--cc=yskoh@mellanox.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).