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xen-devel
RE: [Xen-devel] [Patch] Buffer disk I/O requests
> > How does it compare to just using the SCSI HBA support that got
> > checked in a few days ago (in the qemu-dm 0.9.0 upgrade)?
>
> In our test, the performance of SCSI HBA is better than our patch
> performance in qemu 0.9.0,
Thanks for running the tests.
> But we find the total I/O preformance
> downgrade a lot after upgrade to qemu 0.9.0. We suspect there may be
> some issues in qemu 0.9.0.
Please can you explain in more detail.
> > If we're going to add support for enabling buffering of ioport
> > accesses beyond what we currently special case for the VGA it should
> > be via a generic interface used by qemu to register sets of ports
> > with xen and configure how they will be handled.
>
> Yes, if there are many these buffering cases, using a generic
interface
> is a final solution.
I'd like to see this generic mechanism introduced for more than just
whether writes are buffered or not -- it would be very useful to
register ranges of port or mmio space for handling in different
fashions, e.g.:
* read: forward to handler domain X channel Y
* read: read as zeros
* write: forward to handler domain X channel Y (and flush any buffered)
* write: buffer and forward to domain X channel Y
* write: ignore writes
These hooks would also be very useful for adding debugging/tracing. I
severely dislike our current approach of forwarding anything that
doesn't get picked up in Xen to a single qemu-dm rather than registering
explicit ranges.
Best,
Ian
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