[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] [Patch] Buffer disk I/O requests
Ian Pratt wrote: >>> 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. > We just found the preformance is down when we run the same test cases, but now we don't know why. >>> 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 Agree. A generic mechanism should be introduced in future, because we have found buffering I/O port or MMIO is valuable. However I think our patch is still useful now, after all it obviously improves performance of IDE emulation disk I/O, Best regards, --Weidong _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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