Re: [RFC PATCH v4 0/7] hw/arm/virt: Introduce cpu topology support

[Daniel P . Berrangé]

On Tue, Jun 22, 2021 at 05:34:06PM +0800, Yanan Wang wrote:
> Hi,
> 
> This is v4 of the series [1] that I posted to introduce support for
> generating cpu topology descriptions to guest. Comments are welcome!
> 
> Description:
> Once the view of an accurate virtual cpu topology is provided to guest,
> with a well-designed vCPU pinning to the pCPU we may get a huge benefit,
> e.g., the scheduling performance improvement. See Dario Faggioli's
> research and the related performance tests in [2] for reference. So here
> we go, this patch series introduces cpu topology support for ARM platform.
> 
> In this series, instead of quietly enforcing the support for the latest
> machine type, a new parameter "expose=on|off" in -smp command line is
> introduced to leave QEMU users a choice to decide whether to enable the
> feature or not. This will allow the feature to work on different machine
> types and also ideally compat with already in-use -smp command lines.
> Also we make much stricter requirement for the topology configuration
> with "expose=on".

Seeing this 'expose=on' parameter feels to me like we're adding a
"make-it-work=yes" parameter. IMHO this is just something that should
be done by default for the current machine type version and beyond.
I don't see the need for a parameter to turnthis on, especially since
it is being made architecture specific.


Regards,
Daniel
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