On Tue, 27 May 2025 12:11:40 -0400 Steven Rostedt <[email protected]> wrote:
> But there just happens to be one scenario where this can legitimately > happen. That is on a commit_overrun. A commit overrun is when an interrupt > preempts an event being written to the buffer and then the interrupt adds > so many new events that it fills and wraps the buffer back to the commit. > Any new events would then be dropped and be reported as "missed_events". I'll probably update the commit log, but the way I triggered this was to run: # perf record -o perf-test.dat -a -- trace-cmd record --nosplice -e all -p function hackbench 50 Which causes perf to trigger a bunch of interrupts while trace-cmd enables function tracing and all events. This is on a debug kernel that has lockdep, KASAN and interrupt and preemption disabling events enabled. Basically, this causes a lot to be traced in an interrupt. Enough to fill 1.4 megs of the tracing buffer with events in interrupts before a single event could be recorded. I've never triggered this when those extreme conditions were not there. -- Steve
