Re: [libvirt] [PATCH 0/8] Add perf and Intel CMT feature support
On Tue, Nov 24, 2015 at 02:24:22PM +0100, Jiri Denemark wrote:
On Tue, Nov 17, 2015 at 16:00:40 +0800, Qiaowei Ren wrote:
> The series mainly adds Intel CMT feature support into libvirt. CMT is
> new introduced PQos (Platform Qos) feature to monitor the usage of
> cache by applications running on the platform.
>
> Currently CMT patches has been merged into Linux kernel mainline.
> The CMT implementation in Linux kernel is based on perf mechanism and
> there is no support for perf in libvirt, and so this series firstly
> add perf support into libvirt, including two public API and a set of
> util interfaces. And based on these APIs and interfaces, thie series
> implements CMT perf event support.
>
> TODO:
> 1. This series relys on keeping an open file descriptor for the guest.
> We should add one patch to call sys_perf_event_open again iff libvirtd
> is restarted.
Yes, we should reenable perf events when reconnecting to running
domains. Will we need to remember what events were enabled (in domain
status XML) or is it something we can read back from the kernel?
We need to record it somewhere. I guess this raises the question of
whether we should hide it in status XML, or persist the list of
desired perf events in the real domain XML, so we can have the option
of also having them enabled immediately at startup, without requiring
separate API call.
Regards,
Daniel
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