Jamie Lokier wrote: > Avi Kivity wrote: > >>> And video streaming on some embedded devices with no MMU! (Due to the >>> page cache heuristics working poorly with no MMU, sustained reliable >>> streaming is managed with O_DIRECT and the app managing cache itself >>> (like a database), and that needs AIO to keep the request queue busy. >>> At least, that's the theory.) >>> >> Could use threads as well, no? >> > > Perhaps. This raises another point about AIO vs. threads: > > If I submit sequential O_DIRECT reads with aio_read(), will they enter > the device read queue in the same order, and reach the disk in that > order (allowing for reordering when worthwhile by the elevator)? >
There's no guarantee that any sort of order will be preserved by AIO requests. The same is true with writes. This is what fdsync is for, to guarantee ordering. Regards, Anthony Liguori ------------------------------------------------------------------------- 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
