On Wed, 27 Oct 2021 13:59:08 -0700 Kalesh Singh <kaleshsingh@xxxxxxxxxx> wrote: > Update the tracefs README to describe how hist trigger variables > can be created. > > Signed-off-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx> This looks good to me. Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Thank you! > --- > kernel/trace/trace.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index bc677cd64224..c41b3786401d 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -5628,6 +5628,7 @@ 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" > @@ -5639,6 +5640,16 @@ 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" > -- > 2.33.0.1079.g6e70778dc9-goog > -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
