Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?

[Avi Kivity]

 On 08/03/2010 07:56 PM, Richard W.M. Jones wrote:
> On Tue, Aug 03, 2010 at 07:44:49PM +0300, Avi Kivity wrote:
> >   On 08/03/2010 07:28 PM, Richard W.M. Jones wrote:
> > > I have posted a small patch which makes this 650x faster without
> > > appreciable complication.
> > It doesn't appear to support live migration, or hiding the feature
> > for -M older.
> AFAICT live migration should still work (even assuming someone live
> migrates a domain during early boot, which seems pretty unlikely ...)

Live migration is sometimes performed automatically by management tools, 
which have no idea (nor do they care) what the guest is doing.

> Maybe you mean live migration of the dma_* global variables?  I can
> fix that.

Yes.

> > It's not a good path to follow.  Tomorrow we'll need to load 300MB
> > initrds and we'll have to rework this yet again.
> Not a very good straw man ...  The patch would take ~300ms instead
> of ~115ms, versus something like 2 mins 40 seconds with the current
> method.

It's still 300ms extra time, with a 900MB footprint.

btw, a DMA interface which blocks the guest and/or qemu for 115ms is not 
something we want to introduce to qemu.  dma is hard, doing something 
simple means it won't work very well.

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