Re: Perf: Preserving the event across CPU hotunplug/plug and Creation of an event on offine CPU

[Mukesh Ojha]

Friendly Ping.


On 5/23/2019 6:39 PM, Mukesh Ojha wrote:
> Hi Peter/All,
>
> This is regarding the discussion happen in the past about 
> https://lkml.org/lkml/2018/2/15/1324
>
> Where the exact ask is to allow preserving and creation of events on a 
> offline CPU, so that when the CPU
> comes online it will start counting.
>
> I had a look at your patch too and resolve crash during while trying 
> to create an event on an offline cpu.
>
> In your patch, you seem to disable event when cpu goes offline which 
> is exactly deleting the event
> from the pmu and add when it comes online, it seems to work.
>
> But, For the purpose of allowing the creation of event while CPU is 
> offline is not able to count event while
> CPU coming online, for that i did some change, that did work.
>
> Also, I have query about the events which gets destroyed while CPU is 
> offline and we need to remove them
> once cpu comes online right ? As Raghavendra also queried the same in 
> the above thread.
>
> Don't we need a list where we maintain the events which gets 
> destroyed while CPU is dead ?
> and clean it up when CPU comes online ?
>
> Thanks.
> Mukesh