Messages in this thread |  | | From | Rusty Russell <> | Subject | Re: [PATCH v2 1/5] virtio: add functions for piecewise addition of buffers | Date | Mon, 07 Jan 2013 10:02:57 +1030 |
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Wanlong Gao <gaowanlong@cn.fujitsu.com> writes: > On 01/02/2013 01:03 PM, Rusty Russell wrote: >> Paolo Bonzini <pbonzini@redhat.com> writes: >>> The virtqueue_add_buf function has two limitations: >>> >>> 1) it requires the caller to provide all the buffers in a single call; >>> >>> 2) it does not support chained scatterlists: the buffers must be >>> provided as an array of struct scatterlist; >> >> Chained scatterlists are a horrible interface, but that doesn't mean we >> shouldn't support them if there's a need. >> >> I think I once even had a patch which passed two chained sgs, rather >> than a combo sg and two length numbers. It's very old, but I've pasted >> it below. >> >> Duplicating the implementation by having another interface is pretty >> nasty; I think I'd prefer the chained scatterlists, if that's optimal >> for you. > > I rebased against virtio-next and use it in virtio-scsi, and tested it with 4 targets > virtio-scsi devices and host cpu idle=poll. Saw a little performance regression here.
Sure, but now you should be able to eliminate virtscsi_map_sgl(), right? You should be able to use scsi_out(sc) and scsi_in(sc) directly, which is what Paulo wanted to do...
Right Paulo?
Thanks, Rusty.
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