On Thursday 21 August 2008 16:14, Dave Chinner wrote: > I think that we need to issue explicit unplugs to get the log I/O > dispatched the way we want on all elevators and stop trying to > give elevators implicit hints by abusing the bio types and hoping > they do the right thing.... FWIW, my explicit plugging idea is still hanging around in one of Jens' block trees (actually he refreshed it a couple of months ago). It provides an API for VM or filesystems to plug and unplug requests coming out of the current process, and it can reduce the need to idle the queue. Needs more performance analysis and tuning though. But existing plugging is below the level of the elevators, and should only kick in for at most tens of ms at queue idle events, so it sounds like it may not be your problem. Elevators will need some hint to give priority to specific requests -- either via the current threads's io priority, or information attached to bios. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
