Re: [Xen-devel] Clarification regarding xen toolstack for booting a pv guest

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Aug 11, 2015 at 01:51:10AM +0100, Wei Liu wrote:
> On Mon, Aug 10, 2015 at 05:00:51PM -0700, sainath grandhi wrote:
> > Hello all,
> > 
> > 
> > 
> > I was measuring amount of time taken on host by the Xen toolstack
> > while launching a PV guest.
> > 
> > I notice that there is around 2-3 seconds of time spent on dom0 by
> > toolstack before guest starts executing. Significant amount of time is
> > taken in the function xc_dom_boot_mem_init, around 2 seconds for a
> > guest memory of 2 GB
> > 
> > This code does allocate guest memory and mappings and amount of time
> > this function takes increases proportionally with increasing requested
> > guest memory in the guest config file.
> > 
> > Has anyone noticed similar thing? Is ~2 seconds of wall clock time
> > reasonable for guest memory mapping?
> 
> I guess it is because Dom0 has to balloon down to free up memory for
> guest.
> 
> What is your Xen command line? Have you tried putting
> dom0_mem=512M,max:512M there?
> 

And I forgot to mention there is a patch to make PV guest creation
faster by using superpage and batching.

See 415b58c1 and 826ca36fa3 in xen-unstable tree.

Wei.

> Wei.
> 
> > 
> > Thanks
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel

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