On Thu, Jul 6, 2017 at 3:25 PM, Piotr Dałek <branch@xxxxxxxxxxxxxxxx> wrote: > Is that deep copy an equivalent of what > Jewel librbd did at unspecified point of time, or extra one? It's equivalent / replacement -- not an additional copy. This was changed to support scatter/gather IO API methods which the latest version of QEMU now directly utilizes (eliminating the need for a bounce-buffer copy on every IO). Once we get that librados issue resolved, that initial librbd IO buffer copy will be dropped and librbd will become zero-copy for IO (at least that's the goal). That's why I am recommending that you just assume normal AIO semantics and not try to optimize for Luminous since perhaps the next release will have that implementation detail of the extra copy removed. -- Jason -- 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
