On Mon, Mar 03, 2008 at 08:09:49PM +0200, Avi Kivity wrote: > Jack Steiner wrote: > >The range invalidates have a performance advantage for the GRU. TLB > >invalidates > >on the GRU are relatively slow (usec) and interfere somewhat with the > >performance > >of other active GRU instructions. Invalidating a large chunk of addresses > >with > >a single GRU TLBINVAL operation is must faster than issuing a stream of > >single > >page TLBINVALs. > > > >I expect this performance advantage will also apply to other users of > >mmuops. > > > > In theory this would apply to kvm as well (coalesce tlb flush IPIs, > lookup shadow page table once), but is it really a fast path? What > triggers range operations for your use cases?
Although not frequent, an unmap of a multiple TB object could be quite painful if each page was invalidated individually instead of 1 invalidate for the entire range. This is even worse if the application is threaded and the object has been reference by many GRUs (there are 16 GRU ports per node - each potentially has to be invalidated). Forks (again, not frequent) would be another case. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
