[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 1/9] Xen Share: Simplified I/O Mechanism
On Tue, 2006-06-06 at 15:47 +0100, Harry Butterworth wrote: > On Tue, 2006-06-06 at 15:35 +1000, Rusty Russell wrote: > > This introduces a page "share" mechanism to xen: an alternative to > > both cross-domain binding of event channels, and grant tables. > > Why do you think an alternative to event channels and grant tables is > needed? Fundamentally, I think having a simplified mechanism for inter-domain communication keeps us honest: we can benchmark against it and look at the code size, if nothing else. > Personally, I think there is a need for a more convenient _high-level_ > API that more directly meets the split-drivers' requirements for > inter-domain messaging and bulk data transfer but this seems to me to be > another low-level API and doesn't seem significantly more convenient to > use than grant-tables and event-channels. The isolation it provides forms a better basis for a higher-level mechanism, IMHO. Neither side really knows, or cares, where the events and data are really going to. There is no mapping of other domain's memory, with all the trust and coordination issues that we had to deal with (and didn't completely!) with the current mechanisms. For example, if you wanted to use this as a remote mechanism for communication with another machine, you could. If you wanted to substitute backends without the front end knowing, you could. If the frontend or backend dies, there is no restriction on cleaning up its memory. > Is the n>2-way sharing feature the only benefit over grant-tables or do > you think there are other benefits to your approach? Other than the above theoretical advantages, I found it far easier to implement a Linux driver on top of this, than it was to implement it on top of grant tables, event channel binding and xenbus. Easier to implement means easier to optimize, easier to port, and easier to debug. Hope that clarifies! Rusty. -- ccontrol: http://ccontrol.ozlabs.org _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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