On Wednesday 03 October 2007 19:55, Paul Jackson wrote: > > > Yeah -- cpusets are hierarchical. And some of the use cases for > > > which cpusets are designed are hierarchical. > > > > But partitioning isn't. > > Yup. We've got a square peg and a round hole. An impedance mismatch. > That's the root cause of this entire wibbling session, in my view.
Basically, yeah. > > > To repeat myself, in some cases, such as batch schedulers running in a > > > subset of the CPUs on a large system, the code that knows some of the > > > needs for load balancing does not have system wide control to mandate > > > hard partitioning. The batch scheduler can state where it is depending > > > on load balancing being present, and the system administrator can > > > choose or not to turn off load balancing in the top cpuset, thereby > > > granting or not control over load balancing on the CPUs controlled by > > > the batch scheduler to the batch scheduler. > > > > Why isn't that possible with my approach? > > If I understand your approach to the kernel-to-user interface correctly > (sometimes I doubt I do) then your approach expected some user space code > or person or semi-intelligent equivalent to define a flat partition, > which will then be used to determine the sched domains. > > In the batch scheduler case, running on a large shared system used > perhaps by several departments, no one entity can do that. One person, > perhaps the system admin, knows if they want to give complete control > of some big chunk of CPUs to a batch scheduler. The batch scheduler, > written by someone else far away and long ago, knows which jobs are > actively running on which subsets of the CPUs the batch scheduler is > using. > > There is no single monolithic entity on such systems who knows all and > can dictate all details of a single, flat, system-wide partitioning. OK, so I don't exactly understand you either. To make it simple, can you give a concrete example of a cpuset hierarchy that wouldn't work? > The partitioning has to be sythesized from the combined requests of > several user space entities. That's ok -- this is bread and butter > work for cpusets. OK, so to really do anything different (from a non-partitioned setup), you would need to set sched_load_balance=0 for the root cpuset? Suppose you do that to hard partition the machine, what happens to newly created tasks like kernel threads or things that aren't in a cpuset? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
