[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] Will the ELI incorporated in theKVM?
From: |
Jan Kiszka |
Subject: |
Re: [Qemu-devel] Will the ELI incorporated in theKVM? |
Date: |
Wed, 19 Sep 2012 16:46:28 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
On 2012-09-19 16:43, Abel Gordon wrote:
>
>> It's imperfect as you need to dedicate a core to pure guest-mode load
>> and cannot run userspace on that core (cannot walk through
>> userspace-based device models e.g.).
>
> That's not correct.
> For the evaluation, we dedicated a core for each guest to maximize the
> performance but this
> is not a requirement. You can over-commit cores and share them across
> multiple VMs. In this case,
> you will be sharing the cycles among all the VMs and the performance per VM
> will be degraded.
> In addition, if you share a core, an interrupt for a guest may be raised
> while the corresponding
> VCPU is not running. Depending on the workload, most of the interrupts will
> be generated while
> the VCPU runs or not.
>
>> and cannot run userspace on that core (cannot walk through
>> userspace-based device models e.g.).
>
> That's not correct.
> We can run any thread (including user-space threads) on the same core we
> run the VMs (VCPU threads).
> In fact, we did that for the ELI evaluation: we shared a single core to run
> the VCPU thread and ALL the host threads (including qemu I/O thread).
>
>> And it requires that magic bar to
>> map the shadow IDT into the guest (hmm, I think Hitachi avoided this).
>
> Hitachi uses a different technique which seems to have the 2 disadvantages
> you previously mentioned while ELI doesn't have these disadvantages.
>
>> It's invasive as it has to change Linux to maintain those isolated slave
>> CPUs. That is, of course, based on code that was published by Hitachi.
>> Yours may differ but will still have to solve the same problems.
>
> ELI does not require isolated/slave CPUs.
>
OK. Show patches.
Jan
--
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux
- [Qemu-devel] Will the ELI incorporated in theKVM?, GaoYi, 2012/09/18
- Re: [Qemu-devel] Will the ELI incorporated in theKVM?, Jan Kiszka, 2012/09/18
- Re: [Qemu-devel] Will the ELI incorporated in theKVM?, Muli Ben-Yehuda, 2012/09/19
- Re: [Qemu-devel] Will the ELI incorporated in theKVM?, Jan Kiszka, 2012/09/19
- Re: [Qemu-devel] Will the ELI incorporated in theKVM?, Avi Kivity, 2012/09/19
- Re: [Qemu-devel] Will the ELI incorporated in theKVM?, Abel Gordon, 2012/09/19
- Re: [Qemu-devel] Will the ELI incorporated in theKVM?,
Jan Kiszka <=
- Re: [Qemu-devel] Will the ELI incorporated in theKVM?, GaoYi, 2012/09/20
- Re: [Qemu-devel] Will the ELI incorporated in theKVM?, Abel Gordon, 2012/09/20
- Re: [Qemu-devel] Will the ELI incorporated in theKVM?, Jan Kiszka, 2012/09/20
- Re: [Qemu-devel] Will the ELI incorporated in theKVM?, Gleb Natapov, 2012/09/20
- Re: [Qemu-devel] Will the ELI incorporated in theKVM?, Avi Kivity, 2012/09/20
- Re: [Qemu-devel] Will the ELI incorporated in theKVM?, Gleb Natapov, 2012/09/20