From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: kurt.hackel@oracle.com, Ian Pratt <Ian.Pratt@eu.citrix.com>,
"Xen-Devel (E-mail)" <xen-devel@lists.xensource.com>,
Tim Deegan <Tim.Deegan@citrix.com>,
Keir Fraser <Keir.Fraser@eu.citrix.com>
Subject: Re: [RFC] Correct/fast timestamping in apps under Xen [1 of 4]: Reliable TSC
Date: Fri, 09 Oct 2009 17:22:43 -0700 [thread overview]
Message-ID: <4ACFD3D3.4000900@goop.org> (raw)
In-Reply-To: <1eed24f4-8ead-42ad-a050-5b8bf338d93f@default>
On 10/09/09 14:35, Dan Magenheimer wrote:
> Excellent! This is an extremely important piece
> of the puzzle now filled in.
>
> Just for completeness, on your machine, what is
> the measurement for raw rdtsc?
>
A naked inline rdtsc is about 30ns, so only about a factor of 3 better.
Which is a surprisingly small improvement given that the full
gettimeofday path has ~150 instructions, including a couple of
multiplies, quite a few jumps and two "lsl" instructions for vgetcpu
(which each cost about 10ns). rdtsc is an expensive instruction...
J
next prev parent reply other threads:[~2009-10-10 0:22 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-02 17:51 [RFC] Correct/fast timestamping in apps under Xen [1 of 4]: Reliable TSC Dan Magenheimer
2009-10-07 21:07 ` Dan Magenheimer
2009-10-08 6:45 ` Keir Fraser
2009-10-08 6:54 ` Keir Fraser
2009-10-08 9:13 ` Tim Deegan
2009-10-08 9:22 ` Keir Fraser
2009-10-08 16:24 ` Dan Magenheimer
2009-10-09 9:34 ` Tim Deegan
2009-10-09 14:38 ` Dan Magenheimer
2009-10-12 9:51 ` Tim Deegan
2009-10-09 20:28 ` Jeremy Fitzhardinge
2009-10-09 21:35 ` Dan Magenheimer
2009-10-10 0:22 ` Jeremy Fitzhardinge [this message]
2009-10-10 2:36 ` Dan Magenheimer
2009-10-10 5:55 ` Jeremy Fitzhardinge
2009-10-10 6:35 ` Keir Fraser
2009-10-10 14:22 ` Dan Magenheimer
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=4ACFD3D3.4000900@goop.org \
--to=jeremy@goop.org \
--cc=Ian.Pratt@eu.citrix.com \
--cc=Keir.Fraser@eu.citrix.com \
--cc=Tim.Deegan@citrix.com \
--cc=dan.magenheimer@oracle.com \
--cc=kurt.hackel@oracle.com \
--cc=xen-devel@lists.xensource.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.