From: Andrew Theurer <habanero@linux.vnet.ibm.com>
To: kvm@vger.kernel.org
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Subject: gettimeofday() vsyscall for kvm-clock?
Date: Mon, 21 May 2012 15:26:54 -0500 [thread overview]
Message-ID: <4FBAA50E.4010006@linux.vnet.ibm.com> (raw)
Wondering if a user-space gettimofday() for kvm-clock has been
considered before. I am seeing a pretty large difference in performance
between tsc and kvm-clock. I have to assume at least some of this is
due to the mode switch for kvm-clock. Here are the results:
(this is a 16 vCPU VM on a 16 thread 2S Nehalem-EP host, looped
gettimeofday() calls on all vCPUs)
tsc: .0645 usec per call
kvm-clock: .4222 usec per call (6.54x)
-Andrew Theurer
next reply other threads:[~2012-05-21 20:28 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-21 20:26 Andrew Theurer [this message]
2012-05-21 20:36 ` gettimeofday() vsyscall for kvm-clock? Marcelo Tosatti
2012-05-21 22:13 ` Andrew Theurer
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=4FBAA50E.4010006@linux.vnet.ibm.com \
--to=habanero@linux.vnet.ibm.com \
--cc=kvm@vger.kernel.org \
--cc=mtosatti@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.