Re: [PATCH] qemu-kvm: introduce cpu_start/cpu_stop commands

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From: Chris Wright <chrisw@sous-sol.org>
To: Anthony Liguori <aliguori@linux.vnet.ibm.com>
Cc: Chris Wright <chrisw@sous-sol.org>,
	Anthony Liguori <aliguori@us.ibm.com>,
	qemu-devel@nongnu.org, kvm@vger.kernel.org
Subject: Re: [PATCH] qemu-kvm: introduce cpu_start/cpu_stop commands
Date: Mon, 22 Nov 2010 15:56:51 -0800	[thread overview]
Message-ID: <20101122235651.GD10050@sequoia.sous-sol.org> (raw)
In-Reply-To: <4CEB006C.8010407@linux.vnet.ibm.com>

* Anthony Liguori (aliguori@linux.vnet.ibm.com) wrote:
> On 11/22/2010 05:04 PM, Chris Wright wrote:
> >* Anthony Liguori (aliguori@us.ibm.com) wrote:
> >>qemu-kvm vcpu threads don't response to SIGSTOP/SIGCONT.  Instead of teaching
> >>them to respond to these signals, introduce monitor commands that stop and start
> >>individual vcpus.
> >In the past SIGSTOP has introduced time skew.  Have you verified this
> >isn't an issue.
> 
> Time skew is a big topic.  Are you talking about TSC drift,
> pit/rtc/hpet drift, etc?

Sorry to be vague, but it's been long enough that I don't recall
the details.  The guest kernel's clocksource effected how timekeeping
progressed across STOP/CONT (was probably missing qemu based timer ticks).
While this is not the same, made me wonder if you'd tested against that.

> It's certainly going to stress periodic interrupt catch up code.

Heh, call it a feature for autotest ;)

thanks,
-chris

WARNING: multiple messages have this Message-ID (diff)

From: Chris Wright <chrisw@sous-sol.org>
To: Anthony Liguori <aliguori@linux.vnet.ibm.com>
Cc: Chris Wright <chrisw@sous-sol.org>,
	Anthony Liguori <aliguori@us.ibm.com>,
	qemu-devel@nongnu.org, kvm@vger.kernel.org
Subject: [Qemu-devel] Re: [PATCH] qemu-kvm: introduce cpu_start/cpu_stop commands
Date: Mon, 22 Nov 2010 15:56:51 -0800	[thread overview]
Message-ID: <20101122235651.GD10050@sequoia.sous-sol.org> (raw)
In-Reply-To: <4CEB006C.8010407@linux.vnet.ibm.com>

* Anthony Liguori (aliguori@linux.vnet.ibm.com) wrote:
> On 11/22/2010 05:04 PM, Chris Wright wrote:
> >* Anthony Liguori (aliguori@us.ibm.com) wrote:
> >>qemu-kvm vcpu threads don't response to SIGSTOP/SIGCONT.  Instead of teaching
> >>them to respond to these signals, introduce monitor commands that stop and start
> >>individual vcpus.
> >In the past SIGSTOP has introduced time skew.  Have you verified this
> >isn't an issue.
> 
> Time skew is a big topic.  Are you talking about TSC drift,
> pit/rtc/hpet drift, etc?

Sorry to be vague, but it's been long enough that I don't recall
the details.  The guest kernel's clocksource effected how timekeeping
progressed across STOP/CONT (was probably missing qemu based timer ticks).
While this is not the same, made me wonder if you'd tested against that.

> It's certainly going to stress periodic interrupt catch up code.

Heh, call it a feature for autotest ;)

thanks,
-chris

next prev parent reply	other threads:[~2010-11-22 23:57 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-11-22 23:00 [PATCH] qemu-kvm: introduce cpu_start/cpu_stop commands Anthony Liguori
2010-11-22 23:00 ` [Qemu-devel] " Anthony Liguori
2010-11-22 23:03 ` Anthony Liguori
2010-11-22 23:03   ` [Qemu-devel] " Anthony Liguori
2010-11-22 23:04 ` Chris Wright
2010-11-22 23:04   ` [Qemu-devel] " Chris Wright
2010-11-22 23:44   ` Anthony Liguori
2010-11-22 23:44     ` [Qemu-devel] " Anthony Liguori
2010-11-22 23:56     ` Chris Wright [this message]
2010-11-22 23:56       ` Chris Wright
2010-11-23  0:24       ` Anthony Liguori
2010-11-23  0:24         ` [Qemu-devel] " Anthony Liguori
2010-11-23  6:35   ` Avi Kivity
2010-11-23  6:41 ` [Qemu-devel] " Avi Kivity
2010-11-23  6:41   ` Avi Kivity
2010-11-23  8:16   ` Dor Laor
2010-11-23  8:16     ` Dor Laor
2010-11-23 13:57     ` Anthony Liguori
2010-11-23 13:57       ` Anthony Liguori
2010-11-23 13:51   ` Anthony Liguori
2010-11-23 13:51     ` Anthony Liguori
2010-11-23 14:00     ` Avi Kivity
2010-11-23 14:00       ` Avi Kivity
2010-11-23 14:24       ` Anthony Liguori
2010-11-23 14:24         ` Anthony Liguori
2010-11-23 14:35         ` Avi Kivity
2010-11-23 14:35           ` Avi Kivity
2010-11-23  7:29 ` Gleb Natapov
2010-11-23  7:29   ` [Qemu-devel] " Gleb Natapov

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