Update the tracefs README to describe how hist trigger variables can be created.

Signed-off-by: Kalesh Singh kaleshsingh@google.com Acked-by: Masami Hiramatsu mhiramat@kernel.org --- Changes in v2: - Add Masami's Acked-by.

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"

On Thu, 28 Oct 2021 12:57:58 -0700 Kalesh Singh kaleshsingh@google.com wrote:

Add tests for the parsing of hist trigger expressions; and to validate expression evaluation.

Signed-off-by: Kalesh Singh kaleshsingh@google.com

This looks good to me.

Acked-by: Masami Hiramatsu mhiramat@kernel.org

Thank you!

---

Changes in v6:

• Read the expression result from the trigger file, instead of creating a histogram to print the value.

Changes in v5:

• Add README pattern to requires tag, per Masami

Changes in v3:

• Remove .sym-offset error check tests

Changes in v2:

• Add Namhyung's Reviewed-by
• Update comment to clarify err_pos in "Too many subexpressions" test

.../trigger/trigger-hist-expressions.tc | 65 +++++++++++++++++++ 1 file changed, 65 insertions(+) create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-expressions.tc

diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-expressions.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-expressions.tc new file mode 100644 index 000000000000..33eb79589b32 --- /dev/null +++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-expressions.tc @@ -0,0 +1,65 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 +# description: event trigger - test histogram expression parsing +# requires: set_event events/sched/sched_process_fork/trigger events/sched/sched_process_fork/hist error_log "<var1>=<field|var_ref|numeric_literal>":README

+fail() { #msg

• echo $1
• exit_fail

+}

+test_hist_expr() { # test_name expression expected_val

• trigger="events/sched/sched_process_fork/trigger"
• reset_trigger_file $trigger
• echo "Test hist trigger expressions - $1"
• echo "hist:keys=common_pid:x=$2" > $trigger
• for i in `seq 1 10` ; do ( echo "forked" > /dev/null); done
• x=`grep -o 'x=[[:digit:]]*' $trigger | awk -F= '{ print $2 }'`
• actual=$(( x + 0 )) # To print negative numbers correctly
• if [ $actual != $3 ]; then

•    fail "Failed hist trigger expression evaluation: Expression: $2 Expected: $3, Actual: $actual"
  

• fi
• reset_trigger_file $trigger

+}

+check_error() { # test_name command-with-error-pos-by-^

• trigger="events/sched/sched_process_fork/trigger"
• echo "Test hist trigger expressions - $1"
• ftrace_errlog_check 'hist:sched:sched_process_fork' "$2" $trigger

+}

+test_hist_expr "Variable assignment" "123" "123"

+test_hist_expr "Subtraction not associative" "16-8-4-2" "2"

+test_hist_expr "Division not associative" "64/8/4/2" "1"

+test_hist_expr "Same precedence operators (+,-) evaluated left to right" "16-8+4+2" "14"

+test_hist_expr "Same precedence operators (*,/) evaluated left to right" "4*3/2*2" "12"

+test_hist_expr "Multiplication evaluated before addition/subtraction" "4+3*2-2" "8"

+test_hist_expr "Division evaluated before addition/subtraction" "4+6/2-2" "5"

+# Division by zero returns -1 +test_hist_expr "Handles division by zero" "3/0" "-1"

+# err pos for "too many subexpressions" is dependent on where +# the last subexpression was detected. This can vary depending +# on how the expression tree was generated. +check_error "Too many subexpressions" 'hist:keys=common_pid:x=32+^10*3/20-4' +check_error "Too many subexpressions" 'hist:keys=common_pid:x=^1+2+3+4+5'

+check_error "Unary minus not supported in subexpression" 'hist:keys=common_pid:x=-(^1)+2'

+exit 0

2.33.0.1079.g6e70778dc9-goog