From: Avi Kivity <avi@redhat.com>
To: Erik Jacobson <erikj@sgi.com>
Cc: kvm@vger.kernel.org
Subject: Re: slow guest performance with build load, looking for ideas
Date: Mon, 29 Jun 2009 00:28:10 +0300 [thread overview]
Message-ID: <4A47E06A.7040700@redhat.com> (raw)
In-Reply-To: <20090628190500.GA7347@sgi.com>
On 06/28/2009 10:05 PM, Erik Jacobson wrote:
>>> * In some of the timing runs on this system, the "real time" reported by
>>> the time command was off by 10 to 11 times. Issues were found in
>>> the messages file that seemed to relate to this including HUGE time
>>> adjustments by NTP and kernel hrtimer 'interrupt too slow' messages.
>>> This specific problem seems to be intermittent.
>>>
>> This is on the host? It can easily ruin your day.
>>
>
> This was in the guest.
>
Ok. Please keep ntp off in the guest and verify the guest says it uses
kvmclock.
>> Can you post kvm_stat output during the run?
>>
>
> Sure, I'll try to get time on the system again next week and post in
> to the thread again. We'll still have the issue with the non-sequential
> nodes and incorrect representation of memory for this two-socket
> Nehalem system. I don't think that patch has made it in to the kernel.
>
> Thanks for replying back.
>
> If you have any other things you'd suggest trying, I'm game to give it a
> whirl. Someone suggested trying to export a whole PCI device to the guest.
> I won't be able to do that on this machine, maybe later when I have physical
> access to the system. Besides, that exercise might not poke at what I'm
> interested in anyway.
>
Shouldn't be needed. It's sufficient to export an LVM volume with
cache=none:
-drive file=/dev/vg/lv,cache=none,if=virtio
> Others suggested some potential settings EPT (Extended Page Table) and
> VPID (Virtual Path Identifier?) but I don't see where these settings are
> exposed (they aren't, for example, in this system's BIOS).
>
Look in /sys/modules/kvm_intel/paramters, ept and vpid should default to
enabled.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
next prev parent reply other threads:[~2009-06-28 21:27 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-12 21:04 slow guest performance with build load, looking for ideas Erik Jacobson
2009-06-14 9:33 ` Avi Kivity
2009-06-15 14:15 ` Erik Jacobson
2009-06-15 14:24 ` Avi Kivity
2009-06-15 15:25 ` Michael Tokarev
2009-06-15 15:27 ` Avi Kivity
2009-06-16 7:03 ` Michael Tokarev
2009-06-16 8:07 ` Avi Kivity
2009-06-18 23:07 ` Erik Jacobson
2009-06-28 14:17 ` Avi Kivity
2009-06-28 19:05 ` Erik Jacobson
2009-06-28 21:28 ` Avi Kivity [this message]
2009-07-01 21:41 ` Erik Jacobson
2009-07-02 5:48 ` Avi Kivity
2009-07-02 9:41 ` Avi Kivity
2009-07-03 15:43 ` Mark McLoughlin
2009-07-03 16:28 ` Erik Jacobson
2009-07-09 2:36 ` Erik Jacobson
2009-07-09 7:48 ` Avi Kivity
2009-07-09 18:01 ` Erik Jacobson
2009-07-12 8:38 ` Avi Kivity
2009-07-16 12:20 ` Jes Sorensen
2009-07-25 14:33 ` Avi Kivity
2009-07-03 10:41 ` Matty
2009-07-05 8:07 ` Avi Kivity
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