On Mon, 2009-05-04 at 11:49 +0930, Rusty Russell wrote: > On Mon, 27 Apr 2009 05:13:53 pm Dor Laor wrote: > > Mark McLoughlin wrote: > > > Hi Rusty, > > > > > > On Thu, 2008-12-18 at 17:10 +0000, Mark McLoughlin wrote: > > > > > >> Add a new feature flag for indirect ring entries. These are ring > > >> entries which point to a table of buffer descriptors. > > >> > > >> The idea here is to increase the ring capacity by allowing a larger > > >> effective ring size whereby the ring size dictates the number of > > >> requests that may be outstanding, rather than the size of those > > >> requests. > > OK, just so we track our mistakes. > > 1) virtio_rings must be physically contiguous, even though they actually > have two independent parts. > 2) The number of elements in a ring must be a power of 2. > 3) virtio_pci tells the guest what number of elements to use. > 4) The guest has to allocate that much physically contiguous memory, or fail. > > In practice, 128 elements = 2 pages, 256 elements = 3 pages, 512 elements > = 5 pages. Order 1, order 2, order 3 under Linux. 1 is OK, 2 is iffy, 3 is > hard. > > Blocked from doing the simpler thing, we've decided to go with a layer > of indirection. But the patch is simple and clean, so there's nothing > fundamental to object to. Still have one FIXME in the patch worth looking at - at what point should we use an indirect entry rather than consuming N entries? > I can't find 3/3, did it go missing? Following up with all three patches again. Cheers, Mark. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
