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 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).