From: Glauber Costa <glommer@redhat.com>
To: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, avi@redhat.com
Subject: [PATCH v2 0/2] Automatically grab wallclock time updates from hypervisor
Date: Wed,  2 Sep 2009 10:34:56 -0400
Message-Id: <1251902098-8660-1-git-send-email-glommer@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1164
Lines: 29

i folks,

In this proposed patch, I am introducing a worker fired by kvmclock that updates
guest wallclock periodically to reflect changes in the host's wallclock. With this
patch, a large pool of VMs will no longer have to run NTP in all of its guests.

The worker does that at a configurable interval, with a minimum granularity of 1
second. So, although not exactly cheap, the msr write needed to get an updated
wallclock value won't pose a heavy burden on the system.

It is also possible to disable it completely if this behaviour is undesired for
a specific scenario.

Changes from v1:
 * disabled by default
 * adjust clock in a loop, to prevent agaist host scheduling.

diffstat follows:

 arch/x86/include/asm/kvm_para.h |    6 +++
 arch/x86/kernel/kvmclock.c      |   85 ++++++++++++++++++++++++++++++++++----
 kernel/sysctl.c                 |   13 ++++++
 3 files changed, 95 insertions(+), 9 deletions(-)

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/