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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
| commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
| tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/trace/events-nmi.rst | |
| parent | Initial commit. (diff) | |
| download | linux-5d1646d90e1f2cceb9f0828f4b28318cd0ec7744.tar.xz linux-5d1646d90e1f2cceb9f0828f4b28318cd0ec7744.zip | |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/trace/events-nmi.rst')
| -rw-r--r-- | Documentation/trace/events-nmi.rst | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/Documentation/trace/events-nmi.rst b/Documentation/trace/events-nmi.rst new file mode 100644 index 000000000..9e0a7289d --- /dev/null +++ b/Documentation/trace/events-nmi.rst @@ -0,0 +1,45 @@ +================ +NMI Trace Events +================ + +These events normally show up here: + + /sys/kernel/debug/tracing/events/nmi + + +nmi_handler +----------- + +You might want to use this tracepoint if you suspect that your +NMI handlers are hogging large amounts of CPU time. The kernel +will warn if it sees long-running handlers:: + + INFO: NMI handler took too long to run: 9.207 msecs + +and this tracepoint will allow you to drill down and get some +more details. + +Let's say you suspect that perf_event_nmi_handler() is causing +you some problems and you only want to trace that handler +specifically. You need to find its address:: + + $ grep perf_event_nmi_handler /proc/kallsyms + ffffffff81625600 t perf_event_nmi_handler + +Let's also say you are only interested in when that function is +really hogging a lot of CPU time, like a millisecond at a time. +Note that the kernel's output is in milliseconds, but the input +to the filter is in nanoseconds! You can filter on 'delta_ns':: + + cd /sys/kernel/debug/tracing/events/nmi/nmi_handler + echo 'handler==0xffffffff81625600 && delta_ns>1000000' > filter + echo 1 > enable + +Your output would then look like:: + + $ cat /sys/kernel/debug/tracing/trace_pipe + <idle>-0 [000] d.h3 505.397558: nmi_handler: perf_event_nmi_handler() delta_ns: 3236765 handled: 1 + <idle>-0 [000] d.h3 505.805893: nmi_handler: perf_event_nmi_handler() delta_ns: 3174234 handled: 1 + <idle>-0 [000] d.h3 506.158206: nmi_handler: perf_event_nmi_handler() delta_ns: 3084642 handled: 1 + <idle>-0 [000] d.h3 506.334346: nmi_handler: perf_event_nmi_handler() delta_ns: 3080351 handled: 1 + |