At Thu, 12 Jul 2007 16:07:03 +0100, Sam Mason wrote: > > On Thu, Jul 12, 2007 at 04:41:59PM +0200, Neal H. Walfield wrote: > > General-purpose systems include both interactive systems, such as PDAs > > and Desktops, as well as small to medium-sized servers. Although many > > applications that run on such systems have timeliness properties, > > efficient use of available resources is more important than > > schedulability (i.e., meeting deadlines). > > I tend to use my computer for listening to music and playing videos > and tend to get annoyed when the music skips or frames are dropped. > Thus timeliness is as important as overall utilisation for some of my > workloads. > > If utilisation was all that mattered, we'd still be with cooperative > multi-threading wouldn't we?
Timeliness is very important, however, the cost of providing hard real-time guarantees is high. It lowers resource use efficiency by making dynamic reallocation more difficult, and completely changes the way in which programs are written--you have to optimize for the worst case rather than the average case. I think that it is desirable to provide an interface that allows applications to request specific schedules. This is mostly lacking in most general-purpose operating systems. What mechanisms are available are generally closely guarded. This is because there is no middle-ground between requesting a specific schedule and guaranteeing or rejecting it. It would be useful is having a way to express: insofar as it is possible given the available resources and the other demands and their relative priorities, I would like this schedule. Thanks, Neal _______________________________________________ L4-hurd mailing list [email protected] http://lists.gnu.org/mailman/listinfo/l4-hurd
