The current RADOS behavior is that reads (on any given object) are always processed in the order they are submitted by the client. This causes a few headaches for the cache tiering that it would be nice to avoid. It also occurs to me that there are likely cases where we could go a lot faster by not strictly ordering things. For example, a stat can respond more quickly than a large read, and some reads may hit cache while others go to disk. This doesn't happen currently because of the (lame) way we do reads synchronously, but hope that can change too. I propose we drop this semantic. If a client wants reads to have a strict ordering, they can set the existing RWORDERED flag (which also orders them with respect to writes). That's not the most general thing ever, but I'm not sure we care about callers who want reads ordered with respect to each other but not writes. The real question is whether there are any users that want/need this currently. I can't think of any offhand. In several places we submit multiple *writes* and expect them to be strictly ordered (e.g., we set a completion on teh last write only). I don't think we do this anywhere for reads though... Josh, Yehuda, Jason--can you think of any in RBD or RGW that would depend on this? sage -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
