Re: [Xen-devel] weird hvm performance issue.

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 29/1/07 18:08, "Luke S. Crawford" <lsc@xxxxxxxxx> wrote:

> The CPU usage of qemu-dm correlates with the speed of the scroll;  exiting
> from 
> the xm console does not appear to effect the cpu usage of qemu-dm-  it
> will drop to 1% after several minutes.
> 
> any ideas what is going on here?  any ideas how I could debug this
> further?

This kind of thing can be a pain to debug. Perhaps instrument qemu-dm and
find out interesting things like how often its select() call returns due to
an event on a file descriptor rather than due to hitting the timeout?

Does the slowness happen if you are using the emulated network device at the
same time (i.e., does the event to kick back to normal behaviour have to be
a console event)?

I guess something may have crept in when we moved to using qemu's
asynchronous block i/o code...

 -- Keir



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