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-rw-r--r--kernel/trace/trace.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 0d12dbd..6cf8fd0 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3813,6 +3813,9 @@ static const char readme_msg[] =
#ifdef CONFIG_TRACER_SNAPSHOT
"\t\t snapshot\n"
#endif
+#ifdef CONFIG_HIST_TRIGGERS
+ "\t\t hist (see below)\n"
+#endif
"\t example: echo traceoff > events/block/block_unplug/trigger\n"
"\t echo traceoff:3 > events/block/block_unplug/trigger\n"
"\t echo 'enable_event:kmem:kmalloc:3 if nr_rq > 1' > \\\n"
@@ -3828,6 +3831,20 @@ static const char readme_msg[] =
"\t To remove a trigger with a count:\n"
"\t echo '!<trigger>:0 > <system>/<event>/trigger\n"
"\t Filters can be ignored when removing a trigger.\n"
+#ifdef CONFIG_HIST_TRIGGERS
+ " hist trigger\t- If set, event hits are aggregated into a hash table\n"
+ "\t Format: hist:keys=<field1>\n"
+ "\t [:size=#entries]\n"
+ "\t [if <filter>]\n\n"
+ "\t When a matching event is hit, an entry is added to a hash\n"
+ "\t table using the key named, and the value of a sum called\n"
+ "\t 'hitcount' is incremented. Keys correspond to fields in the\n"
+ "\t event's format description. Keys can be any field. The\n"
+ "\t 'size' parameter can be used to specify more or fewer than\n"
+ "\t the default 2048 entries for the hashtable size.\n\n"
+ "\t Reading the 'hist' file for the event will dump the hash\n"
+ "\t table in its entirety to stdout."
+#endif
;
static ssize_t
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