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| author | Kalesh Singh <kaleshsingh@google.com> | 2021-10-29 11:33:29 -0700 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2021-11-01 20:46:52 -0400 |
| commit | 6a6e5ef2b27f45c15cca569a0825dfd75f564c35 (patch) | |
| tree | e37b08ae6f409e20b35207cebe55a585deb50114 /kernel/trace/trace.c | |
| parent | 0ca6d12c9768ee15e6c7d65ddb5cb35c05946e1e (diff) | |
tracing/histogram: Document hist trigger variables
Update the tracefs README to describe how hist trigger variables
can be created.
Link: https://lkml.kernel.org/r/20211029183339.3216491-4-kaleshsingh@google.com
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/trace.c')
| -rw-r--r-- | kernel/trace/trace.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 985390cb8441..31a4632f9af1 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5606,6 +5606,7 @@ static const char readme_msg[] = #ifdef CONFIG_HIST_TRIGGERS " hist trigger\t- If set, event hits are aggregated into a hash table\n" "\t Format: hist:keys=<field1[,field2,...]>\n" + "\t [:<var1>=<field|var_ref|numeric_literal>[,<var2>=...]]\n" "\t [:values=<field1[,field2,...]>]\n" "\t [:sort=<field1[,field2,...]>]\n" "\t [:size=#entries]\n" @@ -5617,6 +5618,16 @@ static const char readme_msg[] = "\t common_timestamp - to record current timestamp\n" "\t common_cpu - to record the CPU the event happened on\n" "\n" + "\t A hist trigger variable can be:\n" + "\t - a reference to a field e.g. x=current_timestamp,\n" + "\t - a reference to another variable e.g. y=$x,\n" + "\t - a numeric literal: e.g. ms_per_sec=1000,\n" + "\t - an arithmetic expression: e.g. time_secs=current_timestamp/1000\n" + "\n" + "\t hist trigger aritmethic expressions support addition(+), subtraction(-),\n" + "\t multiplication(*) and division(/) operators. An operand can be either a\n" + "\t variable reference, field or numeric literal.\n" + "\n" "\t When a matching event is hit, an entry is added to a hash\n" "\t table using the key(s) and value(s) named, and the value of a\n" "\t sum called 'hitcount' is incremented. Keys and values\n" |