All of lore.kernel.org
 help / color / mirror / Atom feed
From: Per Oberg <pero@wolfram.com>
To: Philippe Gerum <rpm@xenomai.org>
Cc: 송대영 <daeyoungsong@cnu.ac.kr>, xenomai <xenomai@xenomai.org>
Subject: Re: Xenomai Mercury and PREEMPT_RT
Date: Tue, 7 May 2019 01:53:35 -0500 (CDT)	[thread overview]
Message-ID: <1907767262.9872848.1557212015078.JavaMail.zimbra@wolfram.com> (raw)
In-Reply-To: <4c39d8ca-3c98-4b35-6b06-2013dc80134b@xenomai.org>


----- Den 6 maj 2019, på kl 10:07, xenomai xenomai@xenomai.org skrev:
> On 5/6/19 6:34 AM, 송대영 via Xenomai wrote:
> > [webmailreconf.public.do?24538165]

> > Hello, expert.

> > I have a question about Xenomai Mercury and PREEMPT_RT.
> > Following "Xenomai 3 – An Overview of the Real-Time Framework for
> > Linux", Mercury is based on PREEMPT_RT and only offers API emulation.
> > Is Mercury's latency performance better than PREEMPT_RT?

> No, it merely uses what native preemption provides for.

So, just to be clear. Are you saying that it should be "Just as good" as PREEMPT.RT when the kernel is fully patched? (Whatever that means...)

Now, I don't want to start a flame-war here, that would be stupid. But I really want to know your opinion on this (see for eaxmple claims made in [1]). May we assume that the Mercury performance would be quite close to Cobolt performance ?

And how about communication with hardware communication in a PREEMT_RT setup? Without special RT-drivers what can we expect?  For me it's not about when something can be computed but rather when it can be commuicated.


[1] http://linuxgizmos.com/real-time-linux-explained/

Qute: "While Xenomai performed better on most tests, and offered far less jitter, the differences were not as great as the 300 to 400 percent latency superiority claimed by some Xenomai boosters, said Altenberg. When tests were performed on userspace tasks — which Altenberg says is the most real-world, and therefore the most important, test — the worst-case reaction was about 90 to 95 microseconds for both Xenomai and RTL/PREEMPT.RT, he claimed."


> --
> Philippe.



Per Öberg 


  reply	other threads:[~2019-05-07  6:53 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-06  4:34 Xenomai Mercury and PREEMPT_RT 송대영
2019-05-06  8:07 ` Philippe Gerum
2019-05-07  6:53   ` Per Oberg [this message]
2019-05-16 15:51     ` Philippe Gerum
2019-05-17  7:13       ` Per Oberg
2019-05-17  7:36       ` Per Oberg

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=1907767262.9872848.1557212015078.JavaMail.zimbra@wolfram.com \
    --to=pero@wolfram.com \
    --cc=daeyoungsong@cnu.ac.kr \
    --cc=rpm@xenomai.org \
    --cc=xenomai@xenomai.org \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.