1 ================ 2 NMI Trace Events 3 ================ 4 5 These events normally show up here: 6 7 /sys/kernel/tracing/events/nmi 8 9 10 nmi_handler 11 ----------- 12 13 You might want to use this tracepoint if you suspect that your 14 NMI handlers are hogging large amounts of CPU time. The kernel 15 will warn if it sees long-running handlers:: 16 17 INFO: NMI handler took too long to run: 9.207 msecs 18 19 and this tracepoint will allow you to drill down and get some 20 more details. 21 22 Let's say you suspect that perf_event_nmi_handler() is causing 23 you some problems and you only want to trace that handler 24 specifically. You need to find its address:: 25 26 $ grep perf_event_nmi_handler /proc/kallsyms 27 ffffffff81625600 t perf_event_nmi_handler 28 29 Let's also say you are only interested in when that function is 30 really hogging a lot of CPU time, like a millisecond at a time. 31 Note that the kernel's output is in milliseconds, but the input 32 to the filter is in nanoseconds! You can filter on 'delta_ns':: 33 34 cd /sys/kernel/tracing/events/nmi/nmi_handler 35 echo 'handler==0xffffffff81625600 && delta_ns>1000000' > filter 36 echo 1 > enable 37 38 Your output would then look like:: 39 40 $ cat /sys/kernel/tracing/trace_pipe 41 <idle>-0 [000] d.h3 505.397558: nmi_handler: perf_event_nmi_handler() delta_ns: 3236765 handled: 1 42 <idle>-0 [000] d.h3 505.805893: nmi_handler: perf_event_nmi_handler() delta_ns: 3174234 handled: 1 43 <idle>-0 [000] d.h3 506.158206: nmi_handler: perf_event_nmi_handler() delta_ns: 3084642 handled: 1 44 <idle>-0 [000] d.h3 506.334346: nmi_handler: perf_event_nmi_handler() delta_ns: 3080351 handled: 1 45
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.