Damien, > Makes sense. Though I think it will be hard to define a set of QoS > hints that are useful for a wide range of applications, and even > harder to convert the defined hint classes to CDL descriptors. I fear > that we may end up with the same issues as IO hints/streams. Hints mainly failed because non-Linux OSes had very different expectations about how this was going to work. So that left device vendors in a situation where they had to essentially support 3 different approaches all implemented using the same protocol. The challenge of being a general purpose OS is to come up with concepts that are applicable in a variety of situations. Twiddling protocol fields is the easy part. I have a couple of experienced CDL users that I'd like to talk to and try to get a better idea of what a suitable set of defaults might look like. > This hint applies to all priority classes and levels, that is, for the > CDL case, we can enrich any priority with a hint that specifies the > CDL index to use for an IO. Yeah, I like that approach better. -- Martin K. Petersen Oracle Linux Engineering
