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A comment on Why is printing “B” dramatically slower than printing “#”? (2014). Parent comment

Re:Why is printing “B” dramatically slower than printing “#”... by stephencanon on Thursday September 08, 2016 @09:51AM (#12452972)
It's really an example that we should teach people to use a sampling profiler. anyone can answer this question in a minute or so, no speculation necessary, if they just know what tool to use.
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Re:Why is printing “B” dramatically slower than printing “#”... by LukeShu on Thursday September 08, 2016 @11:27AM (#12453903)
Except the insight of the answer is that the bottleneck is in a different program than suspected. Running the suspect program under a profiler wouldn't yield any answers.

Sure, anyone can find the answer if they already know where to look.

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Re:Why is printing “B” dramatically slower than printing “#”... by stephencanon on Thursday September 08, 2016 @01:17PM (#12454976)
Running the suspect program would show blocked states; even without that, you would simply see no difference, conclude that the problem must lie elsewhere, and switch to looking at a full system profile.

FWIW, I always start with a full system profile including all thread states when debugging mysterious performance issues, precisely because "the problem is in another process" is such a common occurrence. This is also why it's important to use a sampling profiler specifically.

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