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Re: [Qemu-devel] [PATCHv5 0/5] add query-cpu-fast and related s390 chang
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCHv5 0/5] add query-cpu-fast and related s390 changes |
Date: |
Tue, 20 Feb 2018 13:23:29 +0100 |
On Fri, 16 Feb 2018 17:08:36 +0100
Viktor Mihajlovski <address@hidden> wrote:
> v5 synopsis: Split out HMP changes from Patch 2 into Patch 5. Please
> re-review, as I've removed the a-b/r-b from Patch 2
> as well.
>
> This series consolidates patches around a performance issue
> caused by the usage of QMP query-cpus.
>
> A performance issue was found in an OpenStack environment, where
> ceilometer was collecting domain statistics with libvirt. The domain
> statistics reported by libvirt include the vCPU halted state, which
> in turn is retrieved with QMP query-cpus.
>
> This causes two issues:
> 1. Performance: on most architectures query-cpus needs to issue a KVM ioctl
> to find out whether a vCPU was halted. This is not the case for s390
> but query-cpus is always causing the vCPU to exit the VM.
>
> 2. Semantics: on x86 and other architectures, halted is a highly transient
> state, which is likely to have already changed shortly after the state
> information has been retrieved. This is not the case for s390, where
> halted is an indication that the vCPU is stopped, meaning its not
> available to the guest operating system until it has been restarted.
Thanks, queued to s390-next.
- Re: [Qemu-devel] [PATCHv5 2/5] qmp: add query-cpus-fast, (continued)
- [Qemu-devel] [PATCHv5 3/5] qmp: add architecture specific cpu data for query-cpus-fast, Viktor Mihajlovski, 2018/02/16
- [Qemu-devel] [PATCHv5 4/5] qemu-doc: deprecate query-cpus, Viktor Mihajlovski, 2018/02/16
- [Qemu-devel] [PATCHv5 5/5] hmp: change hmp_info_cpus to use query-cpus-fast, Viktor Mihajlovski, 2018/02/16
- [Qemu-devel] [PATCHv5 1/5] qmp: expose s390-specific CPU info, Viktor Mihajlovski, 2018/02/16
- Re: [Qemu-devel] [PATCHv5 0/5] add query-cpu-fast and related s390 changes, Cornelia Huck, 2018/02/19
- Re: [Qemu-devel] [PATCHv5 0/5] add query-cpu-fast and related s390 changes,
Cornelia Huck <=