Re: [Qemu-devel] [PATCH] Add warmup phase for live migration of large memory apps

[Isaku Yamahata <yamahata@valinux.co.jp>]

On Thu, May 12, 2011 at 12:39:22PM +0200, Juan Quintela wrote:
> "Shribman, Aidan" <aidan.shribman@sap.com> wrote:
> >> On Wed, May 11, 2011 at 8:58 AM, Shribman, Aidan 
> >> <aidan.shribman@sap.com> wrote:
> >> > From: Aidan Shribman <aidan.shribman@sap.com>
> >> >
> >> > [PATCH] Add warmup phase for live migration of large memory apps
> >> >
> >> > By invoking "migrate -w <url>" we initiate a background 
> >> live-migration
> >> > transferring of dirty pages continuously until invocation 
> >> of "migrate_end"
> >> > which attempts to complete the live migration operation.
> >> 
> >> What is the purpose of this patch?  How and when do I use it?
> >> 
> >
> > The warmup patch adds none-converging background update of guest
> > memory during live-migration such that on request of live-migration
> > completion (via "migrate_end" command) we get much faster
> > response. This is especially needed when running a payload of large
> > enterprise applications which have high memory demands.
> 
> We should integrate this with Kemari (Kemari is doing something like
> this, just that it has more requirements).  Isaku, do you have any comments?

Yochi and Kei are familiar with Kemari. Not me. Cced to them.


> 
> BTW, what loads have you tested for this?
> 
> if I setup an image with 1GB RAM and a DVD iso image, and do in the
> guest:
> 
> while true; do find /media/cdrom -type f | xargs md5sum; done
> 
> Migration never converges with current code (if you use more than 1GB
> memory, then all the DVD will be cached inside).
> 
> So, I see this only useful for guests that are almost idle, and on that
> case, migration speed is not the bigger of your problems, no?
> 
> Later, Juan.
> 

-- 
yamahata