Laurent Vivier wrote: > Le mercredi 23 avril 2008 à 17:05 +0300, Avi Kivity a écrit : > >> Laurent Vivier wrote: >> >>> These two patches allow to batch writes to MMIO. >>> >>> When kernel has to send MMIO writes to userspace, it stores them >>> in memory until it has to pass the hand to userspace for another >>> reason. This avoids to have too many context switches on operations >>> that can wait. >>> >>> >>> >> Did you obtain any measurable performance benefit? >> > > Well, the problem is how to measure it. Really, I don't know. > > But when I add traces I saw MMIO writes are batched: by group of 170 > (this is the max in a page) at the beginning,
That's the lovely animation. You can time XP startup, or look at system time in 'top' once it stabilizes. Also compare total host_state_reloads to boot in kvm_stat (each costs 5 usec, after discount). > and by group of 10 with XP > when we move a window. > That's probably programming the cirrus blitter, also a candidate for batching, but probably not measurable. Maybe one of those Windows graphics benchmarks which draw tons of rectangles very fast and cause epilepsy seizures. I guess most interesting is e1000, if we need to do more than one mmio to start transmitting. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
