From: Eran Rom <eranr@il.ibm.com>
To: kvm@vger.kernel.org
Subject: Re: guest gettimeofday behavior
Date: Mon, 29 Jun 2009 19:11:32 +0000 (UTC) [thread overview]
Message-ID: <loom.20090629T182016-191@post.gmane.org> (raw)
In-Reply-To: 4A4730B9.1090902@redhat.com
Dor Laor <dlaor <at> redhat.com> writes:
>
> On 06/25/2009 04:25 PM, Eran Rom wrote:
> > Behavior:
> > Running a code doing:
> > t1 = gettimeofday
> > t2 = gettimeofday
> > while t2-t1< 5 minutes {
> > sleep(1)
> > t2 = gettimeofday
> > }
> >
> > Ran it 10 times, each time in a 'newly launched' VM,
> > halting it after the test.
> > 8 out of 10 times the wall clock showed 5 minutes
> > 1 time 4 minutes and 40 seconds
> > 1 time 0 seconds
> >
>
> I'm not sure what's your 'wall clock' value,
> there is not printf in your
> script.
the 'wall clock' is host time.
Here is what I am doing form the host:
#! /bin/bash
date
ssh $GuestIP run_gettimeofday_binary
date
> Nevertheless, the tsc clock is not reliable,
> the host can scale it, or
> go into
> deep sleep state.
indeed my current clock source is tsc
>
> So either use newer kernel with kvmclock (pv)
> or change the clock source
> into rtc/pit
>
No rtc/pit in my available clock sources, however,
I assume its a question of kernel compilation parameters,
is that right?
What is the advantage of rtc/pit/kvmclock (pv)over tsc?
Also, is kvmclock (pv) better than the other two options.
the thing is that I am 'confined' to use 2.6.27,
and if I decide on kvmclock, i will need to add it
'manually'
Thanks,
Eran
> > --
> > To unsubscribe from this list: send the line "unsubscribe kvm" in
> > the body of a message to majordomo <at> vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
>
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo <at> vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>
next prev parent reply other threads:[~2009-06-29 19:11 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-25 13:25 guest gettimeofday behavior Eran Rom
2009-06-28 8:58 ` Dor Laor
2009-06-29 19:11 ` Eran Rom [this message]
2009-06-30 6:54 ` Avi Kivity
2009-06-30 7:48 ` Eran Rom
2009-07-06 8:24 ` Eran Rom
2009-07-07 9:58 ` Eran Rom
2009-07-07 20:12 ` Marcelo Tosatti
2009-07-08 11:51 ` Glauber Costa
2009-07-08 14:07 ` Eran Rom
2009-07-13 7:55 ` Eran Rom
2009-07-16 6:24 ` Eran Rom
2009-06-28 10:45 ` Avi Kivity
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=loom.20090629T182016-191@post.gmane.org \
--to=eranr@il.ibm.com \
--cc=kvm@vger.kernel.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 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).