Re: [PATCH v7 00/17] unwind_user: perf: x86: Deferred unwinding infrastructure

[Ingo Molnar <mingo@kernel.org>]

* Steven Rostedt <rostedt@goodmis.org> wrote:

>       unwind_user: Add user space unwinding API
>       unwind_user: Add frame pointer support
>       unwind_user/x86: Enable frame pointer unwinding on x86
>       perf/x86: Rename and move get_segment_base() and make it global
>       unwind_user: Add compat mode frame pointer support
>       unwind_user/x86: Enable compat mode frame pointer unwinding on x86
>       unwind_user/deferred: Add unwind cache

What is the cost of 'caching' here? Will we double-buffer the tracing 
data before it reaches its single primary tooling user, with no use of 
any actual 'caching', which will be scenario in like 99.9% of the 
everyday usecases when this facility is used?

>       unwind_user/deferred: Add deferred unwinding interface
>       unwind_user/deferred: Make unwind deferral requests NMI-safe
>       perf: Remove get_perf_callchain() init_nr argument
>       perf: Have get_perf_callchain() return NULL if crosstask and user are set
>       perf: Simplify get_perf_callchain() user logic
>       perf: Skip user unwind if the task is a kernel thread.

Please don't leave periods in titles.

Thanks,

	Ingo