On Tue, Oct 09, 2007 at 04:50:47PM -0400, Steven Rostedt wrote: > > I did something like this a while ago for another scheduling project. > > A couple 'possible' optimizations to think about are: > > 1) Only scan the remote runqueues once and keep a local copy of the > > remote priorities for subsequent 'scans'. Accessing the remote > > runqueus (CPU specific cache lines) can be expensive. > > You mean to keep the copy for the next two tries? Yes. But with #2 below, your next try is the runqueue/CPU that is the next best candidate (after the trylock fails). The 'hope' is that there is more than one candidate CPU to push the task to. Of course, you always want to try and find the 'best' candidate. My thoughts were that if you could find ANY cpu to take the task that would be better than sending the IPI everywhere. With multiple runqueues/locks there is no way you can be guaranteed of making the 'best' placement. So, a good placement may be enough. > > 2) When verifying priorities, just perform spin_trylock() on the remote > > runqueue. If you can immediately get it great. If not, it implies > > someone else is messing with the runqueue and there is a good chance > > the data you pre-fetched (curr->Priority) is invalid. In this case > > it might be faster to just 'move on' to the next candidate runqueue/CPU. > > i.e. The next highest priority that the new task can preempt. -- Mike - To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
