From: Anthony Liguori <anthony@codemonkey.ws>
To: Avi Kivity <avi@redhat.com>
Cc: Glauber Costa <glommer@redhat.com>,
Jan Kiszka <jan.kiszka@web.de>,
qemu-devel <qemu-devel@nongnu.org>, kvm <kvm@vger.kernel.org>,
Ulrich Obergfell <uobergfe@redhat.com>
Subject: Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift
Date: Mon, 07 Feb 2011 07:11:29 -0600 [thread overview]
Message-ID: <4D4FEF81.1040603@codemonkey.ws> (raw)
In-Reply-To: <4D4FE6BF.5080502@redhat.com>
On 02/07/2011 06:34 AM, Avi Kivity wrote:
> On 02/04/2011 10:56 AM, Jan Kiszka wrote:
>> >
>> > This should be a rare event. If you are missing 50% of your
>> > notifications, not amount of gradual catchup is going to help you
>> out.
>>
>> But that's the only thing this patch is after: lost ticks at QEMU level.
>
> Most lost ticks will happen at the vcpu level. The iothread has low
> utilization and will therefore be scheduled promptly, whereas the vcpu
> thread may have high utilization and will thus be preempted. When it
> is preempted for longer than the timer tick, we will see vcpu-level
> coalescing. All it takes is 2:1 overcommit to see time go half as
> fast; I don't think you'll ever see that on bare metal.
But that's not to say that doing something about lost ticks in QEMU
isn't still useful.
Regards,
Anthony Liguori
next prev parent reply other threads:[~2011-02-07 13:11 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <480481933.225059.1296734409954.JavaMail.root@zmail07.collab.prod.int.phx2.redhat.com>
[not found] ` <1375835067.226263.1296740625327.JavaMail.root@zmail07.collab.prod.int.phx2.redhat.com>
2011-02-03 15:28 ` [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer emulation to alleviate time drift Jan Kiszka
2011-02-03 20:07 ` Anthony Liguori
2011-02-03 21:24 ` Jan Kiszka
2011-02-04 2:06 ` Anthony Liguori
2011-02-04 8:56 ` Jan Kiszka
2011-02-07 12:34 ` Avi Kivity
2011-02-07 13:11 ` Anthony Liguori [this message]
2011-02-07 13:14 ` Avi Kivity
2011-02-07 13:23 ` Anthony Liguori
2011-02-07 13:34 ` Avi Kivity
2011-02-07 13:41 ` Gleb Natapov
2011-02-07 13:46 ` Avi Kivity
2011-02-07 13:48 ` Gleb Natapov
2011-02-07 13:51 ` Avi Kivity
2011-02-07 13:54 ` Gleb Natapov
2011-02-07 14:10 ` Jan Kiszka
2011-02-07 14:28 ` Anthony Liguori
2011-02-07 14:43 ` Jan Kiszka
2011-02-07 14:54 ` Anthony Liguori
2011-02-07 14:57 ` Jan Kiszka
2011-02-07 15:01 ` Anthony Liguori
2011-02-07 15:08 ` Jan Kiszka
2011-02-07 15:13 ` Avi Kivity
2011-02-07 15:17 ` Jan Kiszka
2011-02-07 15:29 ` Avi Kivity
2011-02-07 19:30 ` Anthony Liguori
2011-02-08 9:11 ` Avi Kivity
2011-02-07 15:20 ` Jan Kiszka
2011-02-07 15:30 ` Avi Kivity
2011-02-07 19:28 ` Anthony Liguori
2011-02-07 14:58 ` Avi Kivity
2011-02-07 15:01 ` Jan Kiszka
2011-02-07 15:08 ` Avi Kivity
2011-02-07 15:14 ` Jan Kiszka
2011-02-07 15:16 ` Avi Kivity
2011-02-07 15:22 ` Anthony Liguori
2011-02-07 15:18 ` Anthony Liguori
2011-02-04 9:52 ` Ulrich Obergfell
2011-02-07 10:44 ` Ulrich Obergfell
2011-02-07 13:24 ` Anthony Liguori
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