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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2016-06-23 12:45:36 -0400
committerSteven Rostedt <rostedt@goodmis.org>2016-09-02 12:47:51 -0400
commite7c15cd8a113335cf7154f027c9c8da1a92238ee (patch)
treeb6f7c3ac217af4203489e874c359c409d63f7c27 /kernel/trace/trace_entries.h
parent8861dd303cba879bae9a9dcee74042fb642bf03b (diff)
tracing: Added hardware latency tracer
The hardware latency tracer has been in the PREEMPT_RT patch for some time. It is used to detect possible SMIs or any other hardware interruptions that the kernel is unaware of. Note, NMIs may also be detected, but that may be good to note as well. The logic is pretty simple. It simply creates a thread that spins on a single CPU for a specified amount of time (width) within a periodic window (window). These numbers may be adjusted by their cooresponding names in /sys/kernel/tracing/hwlat_detector/ The defaults are window = 1000000 us (1 second) width = 500000 us (1/2 second) The loop consists of: t1 = trace_clock_local(); t2 = trace_clock_local(); Where trace_clock_local() is a variant of sched_clock(). The difference of t2 - t1 is recorded as the "inner" timestamp and also the timestamp t1 - prev_t2 is recorded as the "outer" timestamp. If either of these differences are greater than the time denoted in /sys/kernel/tracing/tracing_thresh then it records the event. When this tracer is started, and tracing_thresh is zero, it changes to the default threshold of 10 us. The hwlat tracer in the PREEMPT_RT patch was originally written by Jon Masters. I have modified it quite a bit and turned it into a tracer. Based-on-code-by: Jon Masters <jcm@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/trace_entries.h')
-rw-r--r--kernel/trace/trace_entries.h23
1 files changed, 23 insertions, 0 deletions
diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index 5c30efcda5e6..70d47dd99359 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -322,3 +322,26 @@ FTRACE_ENTRY(branch, trace_branch,
FILTER_OTHER
);
+
+FTRACE_ENTRY(hwlat, hwlat_entry,
+
+ TRACE_HWLAT,
+
+ F_STRUCT(
+ __field( u64, duration )
+ __field( u64, outer_duration )
+ __field_struct( struct timespec, timestamp )
+ __field_desc( long, timestamp, tv_sec )
+ __field_desc( long, timestamp, tv_nsec )
+ __field( unsigned int, seqnum )
+ ),
+
+ F_printk("cnt:%u\tts:%010lu.%010lu\tinner:%llu\touter:%llu\n",
+ __entry->seqnum,
+ __entry->tv_sec,
+ __entry->tv_nsec,
+ __entry->duration,
+ __entry->outer_duration),
+
+ FILTER_OTHER
+);