[Xen-devel] Does Xen force all AIO be synchronous?

["Liang Yang" <multisyncfe991@xxxxxxxxxxx>]

Hi,

I have these questions for a while. As AIO can help improve better 
performance and Linux kernel keeps tunning the AIO path,  more and more IOs 
can be expected to take AIO path instead of regular I/O path.
First Question:
If we consider Xen, do we need to do AIO both in the domain0 and guest 
domains at the same? For example, considering two situations, let a full 
virtualized guest domain still do regular I/O and domain0 (vbd back end 
driver) do AIO; or let both full-virtualized guest domain and domain0 do 
AIO. What is possible performance difference here?
Second Question:
Does Domain0 always wait till AIO data is available and then notify guest 
domain? or Domain0 will issue an interrupt immediately to notify guest 
domain0 when AIO is queued? If the first case is true, then all AIOs will 
become synchronous.
Third Question:
Does Xen hypervisor change the behavior of Linux I/O scheduler more or less?

Four Question:
Will AIO have different performance impact on para-virtualized domain and 
full-virtualized domain respectively?
Thanks,

Liang


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel