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Re: [Qemu-devel] live migration vs device assignment (motivation)
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] live migration vs device assignment (motivation) |
Date: |
Tue, 29 Dec 2015 19:15:23 +0200 |
On Tue, Dec 29, 2015 at 09:04:51AM -0800, Alexander Duyck wrote:
> On Tue, Dec 29, 2015 at 8:46 AM, Michael S. Tsirkin <address@hidden> wrote:
> > On Tue, Dec 29, 2015 at 01:42:14AM +0800, Lan, Tianyu wrote:
> >>
> >>
> >> On 12/25/2015 8:11 PM, Michael S. Tsirkin wrote:
> >> >As long as you keep up this vague talk about performance during
> >> >migration, without even bothering with any measurements, this patchset
> >> >will keep going nowhere.
> >> >
> >>
> >> I measured network service downtime for "keep device alive"(RFC patch V1
> >> presented) and "put down and up network interface"(RFC patch V2 presented)
> >> during migration with some optimizations.
> >>
> >> The former is around 140ms and the later is around 240ms.
> >>
> >> My patchset relies on the maibox irq which doesn't work in the suspend
> >> state
> >> and so can't get downtime for suspend/resume cases. Will try to get the
> >> result later.
> >
> >
> > Interesting. So you sare saying merely ifdown/ifup is 100ms?
> > This does not sound reasonable.
> > Is there a chance you are e.g. getting IP from dhcp?
>
>
> Actually it wouldn't surprise me if that is due to a reset logic in
> the driver. For starters there is a 10 msec delay in the call
> ixgbevf_reset_hw_vf which I believe is present to allow the PF time to
> clear registers after the VF has requested a reset. There is also a
> 10 to 20 msec sleep in ixgbevf_down which occurs after the Rx queues
> were disabled. That is in addition to the fact that the function that
> disables the queues does so serially and polls each queue until the
> hardware acknowledges that the queues are actually disabled. The
> driver also does the serial enable with poll logic on re-enabling the
> queues which likely doesn't help things.
>
> Really this driver is probably in need of a refactor to clean the
> cruft out of the reset and initialization logic. I suspect we have
> far more delays than we really need and that is the source of much of
> the slow down.
>
> - Alex
For ifdown, why is there any need to reset the device at all?
Is it so buffers can be reclaimed?
--
MST
- Re: [Qemu-devel] live migration vs device assignment (motivation), (continued)
- Re: [Qemu-devel] live migration vs device assignment (motivation), Michael S. Tsirkin, 2015/12/14
- Re: [Qemu-devel] live migration vs device assignment (motivation), Dr. David Alan Gilbert, 2015/12/10
- Re: [Qemu-devel] live migration vs device assignment (motivation), Alexander Duyck, 2015/12/10
- Re: [Qemu-devel] live migration vs device assignment (motivation), Lan, Tianyu, 2015/12/13
- Re: [Qemu-devel] live migration vs device assignment (motivation), Alexander Duyck, 2015/12/13
- Re: [Qemu-devel] live migration vs device assignment (motivation), Lan Tianyu, 2015/12/25
- Re: [Qemu-devel] live migration vs device assignment (motivation), Michael S. Tsirkin, 2015/12/25
- Re: [Qemu-devel] live migration vs device assignment (motivation), Lan, Tianyu, 2015/12/28
- Re: [Qemu-devel] live migration vs device assignment (motivation), Michael S. Tsirkin, 2015/12/29
- Re: [Qemu-devel] live migration vs device assignment (motivation), Alexander Duyck, 2015/12/29
- Re: [Qemu-devel] live migration vs device assignment (motivation),
Michael S. Tsirkin <=
- Re: [Qemu-devel] live migration vs device assignment (motivation), Alexander Duyck, 2015/12/29
- Re: [Qemu-devel] live migration vs device assignment (motivation), Alexander Duyck, 2015/12/25
- Re: [Qemu-devel] live migration vs device assignment (motivation), Michael S. Tsirkin, 2015/12/27
- Re: [Qemu-devel] live migration vs device assignment (motivation), Alexander Duyck, 2015/12/27
- Re: [Qemu-devel] live migration vs device assignment (motivation), Michael S. Tsirkin, 2015/12/28
- Re: [Qemu-devel] live migration vs device assignment (motivation), Dong, Eddie, 2015/12/27
- Re: [Qemu-devel] live migration vs device assignment (motivation), Alexander Duyck, 2015/12/27
- Re: [Qemu-devel] live migration vs device assignment (motivation), Michael S. Tsirkin, 2015/12/28
- Re: [Qemu-devel] live migration vs device assignment (motivation), Michael S. Tsirkin, 2015/12/14
- Re: [Qemu-devel] live migration vs device assignment (motivation), Pavel Fedin, 2015/12/28