linux-kernel - perf_event wakeup

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Message-ID: <CAN3rvwA+Dnqj4O79f6rNfO50VjbAC3YwJ7CW2ze2aBLzkSJRgQ@mail.gmail.com>
Date:   Fri, 6 Sep 2019 16:28:24 -0700
From:   Theodore Dubois <tbodt@...gle.com>
To:     a.p.zijlstra@...llo.nl
Cc:     linux-kernel@...r.kernel.org, kernelnewbies@...nelnewbies.org
Subject: perf_event wakeup_events = 0

The man page for perf_event_open(2) says that recent kernels treat a 0
value for wakeup_events the same as 1, which I believe means it will
notify after a single sample. However, strace on perf(1) shows that it
uses wakeup_events=0, and it's definitely not waking up on every
sample (it seems to be waking up every few seconds.)
tools/perf/design.txt says "Normally a notification is generated for
every page filled". Is the documentation wrong, or am I
misunderstanding something?

~Theodore