Re: [PATCH V3 0/6] event synthesization multithreading for perf record

[Ingo Molnar]

* Liang, Kan <kan.liang@xxxxxxxxx> wrote:

> For 'all', do you mean the whole process?

Yeah.

> I think that's the ultimate goal.  Eventually there will be per-CPU recording
> threads created at the beginning of perf record and go through the whole process.
> The plan is to do the multithreading step by step from the simplest case.
> Synthesizing stage is just a start.

So, why not do it like the kernel did: add all the threads, create the percpu 
files, and introduce a 'big perf lock' (big mutex) that is taken for all the 
current non-threaded perf functionality. This should be fairly straightforward to 
do and should be 'obviously correct'.

_Then_ start doing the hard threading work on top of this, like threading the 
synthesizing phase.

Doing the whole per CPU thread setup/teardown for just the synthesizing part of it 
looks like the wrong design.

I.e. what I'm suggesting is no extra threading work, just organizing it in a 
different fashion and increasing the life-time of the per CPU threads from 'perf 
startup' to 'perf shutdown'.

Thanks,

	Ingo