Re: [Qemu-devel] [PATCH 2/3] qmp: add query-cpus-fast

[David Hildenbrand <david@redhat.com>]

On 12.02.2018 13:14, Viktor Mihajlovski wrote:
> From: Luiz Capitulino <lcapitulino@redhat.com>
> 
> The query-cpus command has an extremely serious side effect:
> it always interrupts all running vCPUs so that they can run
> ioctl calls. This can cause a huge performance degradation for
> some workloads. And most of the information retrieved by the
> ioctl calls are not even used by query-cpus.
> 
> This commit introduces a replacement for query-cpus called
> query-cpus-fast, which has the following features:
> 
>  o Never interrupt vCPUs threads. query-cpus-fast only returns
>    vCPU information maintained by QEMU itself, which should be
>    sufficient for most management software needs
> 
>  o Make "halted" field optional: we only return it if the
>    halted state is maintained by QEMU. But this also gives
>    the option of dropping the field in the future (see below)
> 

If I'm not wrong, this comment is superseded by ...

>  o Drop irrelevant fields such as "current", "pc" and "arch"
> 
>  o Drop field "halted" since it can't be provided fast reliably
>    and is too volatile on most architectures to be really useful
> 

this comment :)

>  o Rename some fields for better clarification & proper naming
>    standard>
> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
> Signed-off-by: Viktor Mihajlovski <mihajlov@linux.vnet.ibm.com>

Wondering if we could tweak the old interface with a simple flag "fast =
true".


-- 

Thanks,

David / dhildenb