From: Miroslav Lichvar <mlichvar@redhat.com>
To: Richard Cochran <richardcochran@gmail.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Radim Krcmar <rkrcmar@redhat.com>
Subject: Re: [patch 4/5] PTP: add PTP_SYS_OFFSET emulation via cross timestamps infrastructure
Date: Tue, 24 Jan 2017 09:15:56 +0100 [thread overview]
Message-ID: <20170124081556.GY14227@localhost> (raw)
In-Reply-To: <20170124053243.GA1906@localhost.localdomain>
On Tue, Jan 24, 2017 at 06:32:43AM +0100, Richard Cochran wrote:
> On Mon, Jan 23, 2017 at 09:06:20PM -0200, Marcelo Tosatti wrote:
> > Can you please describe what problem exists with this scheme?
>
> This new kernel code exists just because chrony doesn't implement the
> PRECISE ioctl. Instead of adding new "fake" modes, just teach chrony
> about the better method.
The latest development code of chrony now supports the PRECISE ioctl.
I did some tests with an e1000e NIC (i219) and it seemed the stability
was slightly worse than with the non-PRECISE ioctl, but there was a
400-500ns offset between the two, so it should be much more accurate
(we finally have something that avoids the asymmetry on the PCI-e
bus?). Configuring the refclock with a shorter dpoll should compensate
for the decrease in stability. In any case, there is a "nocrossts"
option to not use the PRECISE ioctl even if it's supported.
--
Miroslav Lichvar
next prev parent reply other threads:[~2017-01-24 8:15 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-20 12:20 [patch 0/5] KVM virtual PTP driver (v3) Marcelo Tosatti
2017-01-20 12:20 ` [patch 1/5] KVM: x86: provide realtime host clock via vsyscall notifiers Marcelo Tosatti
2017-01-20 12:20 ` [patch 2/5] KVM: x86: add KVM_HC_CLOCK_OFFSET hypercall Marcelo Tosatti
2017-01-20 12:20 ` [patch 3/5] kvmclock: export kvmclock clocksource pointer Marcelo Tosatti
2017-01-20 12:55 ` Paolo Bonzini
2017-01-20 12:20 ` [patch 4/5] PTP: add PTP_SYS_OFFSET emulation via cross timestamps infrastructure Marcelo Tosatti
2017-01-20 12:55 ` Paolo Bonzini
2017-01-20 13:07 ` Marcelo Tosatti
2017-01-20 13:36 ` Paolo Bonzini
2017-01-20 13:52 ` Marcelo Tosatti
2017-01-20 14:02 ` Radim Krcmar
2017-01-20 14:23 ` Paolo Bonzini
2017-01-20 14:31 ` Miroslav Lichvar
2017-01-20 18:30 ` Radim Krcmar
2017-01-20 20:25 ` Richard Cochran
2017-01-23 13:19 ` Marcelo Tosatti
2017-01-23 18:44 ` Richard Cochran
2017-01-23 19:44 ` Paolo Bonzini
2017-01-24 5:43 ` Richard Cochran
2017-01-24 11:23 ` Marcelo Tosatti
2017-01-24 11:35 ` Richard Cochran
2017-01-23 23:06 ` Marcelo Tosatti
2017-01-24 5:32 ` Richard Cochran
2017-01-24 8:15 ` Miroslav Lichvar [this message]
2017-01-20 12:20 ` [patch 5/5] PTP: add kvm PTP driver Marcelo Tosatti
2017-01-20 12:58 ` Paolo Bonzini
2017-01-20 13:11 ` Marcelo Tosatti
2017-01-20 14:12 ` Radim Krcmar
2017-01-20 14:20 ` Radim Krcmar
2017-01-20 15:00 ` Marcelo Tosatti
2017-01-20 17:11 ` Paolo Bonzini
2017-01-20 18:08 ` Radim Krcmar
2017-01-20 19:10 ` Marcelo Tosatti
2017-01-21 8:02 ` Paolo Bonzini
2017-01-20 13:10 ` [patch 0/5] KVM virtual PTP driver (v3) Paolo Bonzini
-- strict thread matches above, loose matches on Subject: below --
2017-01-20 14:51 [patch 0/5] KVM virtual PTP driver (v4) Marcelo Tosatti
2017-01-20 14:51 ` [patch 4/5] PTP: add PTP_SYS_OFFSET emulation via cross timestamps infrastructure Marcelo Tosatti
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=20170124081556.GY14227@localhost \
--to=mlichvar@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mtosatti@redhat.com \
--cc=pbonzini@redhat.com \
--cc=richardcochran@gmail.com \
--cc=rkrcmar@redhat.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).