From: Roman Kagan <rkagan@virtuozzo.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: <kvm@vger.kernel.org>, "Denis V. Lunev" <den@openvz.org>,
Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH kvm-unit-tests] KVM: x86: add hyperv clock test case
Date: Fri, 22 Apr 2016 16:32:40 +0300 [thread overview]
Message-ID: <20160422133240.GA9108@rkaganb.sw.ru> (raw)
In-Reply-To: <20160421170157.GA16360@rkaganb.sw.ru>
On Thu, Apr 21, 2016 at 08:01:58PM +0300, Roman Kagan wrote:
> As to the drift problem, I reliably reproduce it, too, but it's a bug
> somewhere in kvm_clock, and the new hyperv ref tsc page now demonstrates
> it by virtue of relying on kvm_clock's values. On my machine I observe
> as much as +14 ppm and I'll try to chase it down, but this is
> independent of the hyperv ref tsc page patchset.
A simple demonstration of it: in a CentOS 7.2 x86_64 guest:
# dmesg | grep -Fw tsc:
[ 0.000000] tsc: Detected 3411.482 MHz processor
[ 2.192473] tsc: Refined TSC clocksource calibration: 3411.532 MHz
The first value is derived from the kvm_clock's tsc_to_system_mul and
tsc_shift, and matches hosts's vcpu->hw_tsc_khz. The second is
calibrated using emulated HPET. The difference is those +14 ppm.
This is on i7-2600, invariant TSC present, TSC scaling not present.
I'll dig further but I'd appreciate any comment on whether it was within
tolerance or not.
Roman.
next prev parent reply other threads:[~2016-04-22 13:47 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-28 14:04 [PATCH kvm-unit-tests] KVM: x86: add hyperv clock test case Paolo Bonzini
2016-01-28 14:04 ` Paolo Bonzini
2016-01-28 14:25 ` Andrey Smetanin
2016-01-28 14:50 ` Paolo Bonzini
2016-01-28 15:53 ` Paolo Bonzini
2016-01-28 18:45 ` Roman Kagan
2016-01-28 18:53 ` Roman Kagan
2016-01-28 21:28 ` Paolo Bonzini
2016-01-28 16:22 ` Roman Kagan
2016-02-03 16:37 ` Paolo Bonzini
2016-02-04 9:33 ` Roman Kagan
2016-02-04 10:13 ` Paolo Bonzini
2016-02-04 11:12 ` Roman Kagan
2016-04-21 17:01 ` Roman Kagan
2016-04-22 13:32 ` Roman Kagan [this message]
2016-04-22 18:08 ` Paolo Bonzini
2016-04-25 8:47 ` Roman Kagan
2016-04-26 10:34 ` Roman Kagan
2016-05-25 18:33 ` Roman Kagan
2016-05-26 14:47 ` Roman Kagan
2016-05-29 22:34 ` Marcelo Tosatti
2016-02-08 15:18 [PATCH 0/4] kvmclock: improve accuracy Paolo Bonzini
2016-02-08 15:18 ` [PATCH 1/4] KVM: x86: rename argument to kvm_set_tsc_khz Paolo Bonzini
2016-02-11 15:01 ` Marcelo Tosatti
2016-02-08 15:18 ` [PATCH 2/4] KVM: x86: rewrite handling of scaled TSC for kvmclock Paolo Bonzini
2016-02-11 15:23 ` Marcelo Tosatti
2016-02-08 15:18 ` [PATCH 3/4] KVM: x86: pass kvm_get_time_scale arguments in hertz Paolo Bonzini
2016-02-08 15:18 ` [PATCH 4/4] KVM: x86: track actual TSC frequency from the timekeeper struct Paolo Bonzini
2016-02-09 18:41 ` Owen Hofmann
2016-02-10 13:57 ` Paolo Bonzini
2016-02-16 13:48 ` Marcelo Tosatti
2016-02-16 14:25 ` Marcelo Tosatti
2016-02-16 16:59 ` Paolo Bonzini
2016-02-19 14:12 ` Marcelo Tosatti
2016-02-19 15:53 ` Paolo Bonzini
2016-02-16 14:00 ` [PATCH 0/4] kvmclock: improve accuracy Marcelo Tosatti
2016-08-31 14:13 [PATCH kvm-unit-tests] KVM: x86: add hyperv clock test case Roman Kagan
2016-09-01 16:07 ` Paolo Bonzini
2016-09-01 16:07 Paolo Bonzini
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=20160422133240.GA9108@rkaganb.sw.ru \
--to=rkagan@virtuozzo.com \
--cc=den@openvz.org \
--cc=kvm@vger.kernel.org \
--cc=mtosatti@redhat.com \
--cc=pbonzini@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 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.