On Tue, Nov 28, 2017 at 11:20:27PM +0300, Denis V. Lunev wrote: > > There's one thing I don't understand in your test case: if you > > just found out that Linux will behave worse if it assumes that > > the VCPUs are sharing a L3 cache, why are you configuring a > > 8-core VCPU topology explicitly? > > > > Do you still see a difference in the numbers if you use "-smp 8" > > with no "cores" and "threads" options? > > > This is quite simple. A lot of software licenses are bound to the amount > of CPU __sockets__. Thus it is mandatory in a lot of cases to set topology > with 1 socket/xx cores to reduce the amount of money necessary to > be paid for the software.
This answers the first question but not the second one. If the answer to the second one is negative, then I don't understand why changing the default makes sense. I would expect qemu by default to be as close to emulating a physical system as possible. If one has to deviate from that for some workloads, that is fine, but probably not a good default. -- MST
