On 2010-12-01 22:38, Sebastian Kayser wrote: > Hi, > > I just stumbled into a glaring pitfall when playing with iodepth=X for > the first time. Was using ioengine=sync (default), increased iodepth > 1 > and wondered briefly why my results didn't change. Thinking about it, > this made perfect sense and the "IO depths" distribution in the result > summary even pointed me to it. > > Nevertheless, it might help others to avoid this alltogether if the man > page paragraph on iodepth would include a small heads up / reference to > ioengines. Example patch attached, not quite sure about the wording for > the verify_async aspect. It's a good idea. Something else to keep in mind is that even with async engines, you can run into this issue. Say in Linux and not setting direct=1, the buffered IO will still be sync. So I think I'll add some wording as well to have the user keep an eye on the achieved IO depths and not just assume that it's running with a depth of X for iodepth=X. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
