On 11 Nov 2013, at 18:01, Paolo Bonzini wrote: > Il 11/11/2013 18:59, Alex Bligh ha scritto: >>> Why is it necessary to push this task down into the host? I don't >>> understand the advantage of this approach except that maybe it works >>> around certain misconfigurations, I/O scheduler quirks, or plain old >>> bugs - all of which should be investigated and fixed at the source >>> instead of adding another layer of code to mask them. >> >> I can see an argument why a guest with two very differently >> performing disks attached might be best served by two worker >> threads, particularly if one such thread was in part CPU bound >> (inventing this use case is left as an exercise for the reader). > > In most cases you want to use aio=native anyway, and then the QEMU > thread pool is entirely bypassed.
'most cases' - really? I thought anything using either qcow2 or ceph won't support that? Also I am guessing if aio=native is used then it by definition won't be CPU bound... :-) From one of the Edinburgh presentations I had thought we were going towards everything using the thread pool (subject to appropriate rearchitecture). -- Alex Bligh
