[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] xen: add persistent grants to xbd_xenbus
On 12/11/12 16:34, Ian Campbell wrote: > On Mon, 2012-11-12 at 09:30 +0000, Roger Pau Monnà wrote: >> >> I will try to perform a similar test with a NetBSD Dom0, but with the >> patch it will probably be a little bit slower than without it (because >> we have to perform the memcpy in the frontend, > > Doesn't the frontend fallback to the same old code as always if the b/e > doesn't advertise the new feature? No, the frontend always uses persistent grants, since it's compatible with a backend not using persistent grants, the frontend will reuse the same grants, and the backend will use the old mechanism of mapping and unmapping them. Actually it seems I was wrong on that, using a persistent frontend with a non-persistent backend lets to a more consistent performance, see the following graph: http://xenbits.xen.org/people/royger/persistent_grants/nonpers_read.png _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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