[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH] Std VGA Performance

  • To: Robert Phillips <rsp.vi.xen@xxxxxxxxx>
  • From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
  • Date: Thu, 25 Oct 2007 16:39:58 +0100
  • Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Thu, 25 Oct 2007 08:40:46 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcgXHUwziqceBIMQEdyb3gAX8io7RQ==
  • Thread-topic: [Xen-devel] [PATCH] Std VGA Performance

On 25/10/07 16:28, "Robert Phillips" <rsp.vi.xen@xxxxxxxxx> wrote:

How much benefit comes from immediate servicing of PIO input ops versus the
massive increase in buffered-io slots? Removing the former optimisation
would certainly make the patch a lot smaller!

Subjectively, the performance improvement appears substantial.  We have tested the code with the stdvga emulation and with and without the increased number of slots. With more slots the screen painting goes from being fast to very fast.

As you've noticed, the increase in number of slots is compensated by the decrease in slot size (so there is no increase in memory use) at the cost of packing (and unpacking) ioreqs as they are written to (and read from) the buffer.

I guess what I’m really interested in is the performance /with/ the increased number of slots and with versus without the stdvga emulation. Since it’s the stdvga emulation that really adds the complexity.

 -- Keir
Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.