On Wed, Nov 11, 2009 at 09:38:17AM -0500, James Carlson wrote: > Blake Jones wrote: > >> Is this new class usable only by ZFS, or is it potentially usable by > >> other kernel tasks as well? It looks to me like it could be used to > >> make work done by networking squeues and STREAMS service procedures more > >> observable. > > > > It is potentially usable by other kernel tasks. There is nothing > > ZFS-specific about the class right now, although it makes some very mild > > assumptions about the characteristics of ZFS' workload (e.g. that it's > > processing many fairly small tasks, rather than a few large ones). > > These assumptions basically just have performance implications, rather > > than correctness ones, and changing them would be fairly straightforward > > -- on the order of adding of a new flag to an interface -- but we didn't > > do so because there were no other current consumers of such > > generalization. > > Nifty; thanks! It sounds like it could end up being quite useful.
The system process and associated LWPs are what give you observability; the regular process framework handles reporting all of the CPU use and microstate accounting data. The trade-off is the cost of microstate accounting; currently, kernel threads don't have it. Once you have an LWP, its recorded. The SDC class itself has no direct effect on observability; it is entirely about CPU-intensive kernel threads "playing well with others". SDC does require microstate accounting, though, which implies an LWP and the attendant observability. > > The "zpool-<poolname>" process is created separately from the scheduling > > class. It allows the CPU time from the ZFS task queues (which are now > > running under SDC) to be more easily observed. > > Just curious: is that process created with a non-zero zoneid_t when the > pool is inside a zone? No; one future direction would be to make zone-created pools both show up as children of zsched and have their worker threads bound to the processor set the zone is bound to. Cheers, - jonathan
