Re: Time to merge scratch/correct-warning-pos into master, perhaps?

[Óscar Fuentes]

Eli Zaretskii <eliz@gnu.org> writes:

>> >> If you want to know the impact of such a change, the correct method is
>> >> to measure representative instances of real-world cases.
>> >
>> > We already did that.  We now want to understand _why_ the new version
>> > is slower, and then try making it faster.
>> 
>> Then I suggest to use Valgrind for collecting performance data at the
>> machine instruction level
>
> AFAIK, Perf is fully capable of collecting performance data on this
> level.

Perf is a sampling profiler and that makes very tricky to get reliable
data for a tiny piece of code within a large application.

> So what will Valgrind gain us, except the need to battle the known
> problems when running Emacs under Valgrind?

Valgrind emulates each instruction and its context (L1/L2 cache misses,
etc.) That's why Valgrind is two orders of magnitude slower than Perf
(and it accounts for a good chunk of the "patience" requirement I
mentioned on my previous message.)

Profiling Emacs with Valgrind should not pose problems, AFAIK.