Re: [Qemu-devel] [PATCH v2 0/3] Make thread pool implementation modular

[Alex Bligh]

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