linux-kernel - [PATCH v2 5/5] perf test trace BTF: Use --sort-events in BTF general tests

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Message-ID: <20250518190957.58932-6-howardchu95@gmail.com>
Date: Sun, 18 May 2025 12:09:57 -0700
From: Howard Chu <howardchu95@...il.com>
To: acme@...nel.org
Cc: mingo@...hat.com,
	namhyung@...nel.org,
	mark.rutland@....com,
	alexander.shishkin@...ux.intel.com,
	jolsa@...nel.org,
	irogers@...gle.com,
	adrian.hunter@...el.com,
	peterz@...radead.org,
	kan.liang@...ux.intel.com,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Howard Chu <howardchu95@...il.com>
Subject: [PATCH v2 5/5] perf test trace BTF: Use --sort-events in BTF general tests

Without the '--sort-events' flag, perf trace doesn't receive and process
events based on their arrival time, thus PERF_RECORD_COMM event that
assigns the correct comm to a PID, may be delivered and processed after
regular samples, causing trace outputs not having a 'comm', e.g.
'mv', instead, having the default PID placeholder, e.g. ':14514'.

Hopefully this answers Namhyung's question in [1].

You can simply justify the statement with this diff: [2].

Now, simply run this command multiple times:
    $ touch /tmp/file1 && sudo /tmp/perf trace -e renameat* -- mv /tmp/file1 /tmp/file2 && rm -f /tmp/file2
And you should see two types of results:

    $ touch /tmp/file1 && sudo /tmp/perf trace -e renameat* -- mv /tmp/file1 /tmp/file2 && rm -f /tmp/file2
    [debug] deliver
    [debug] machine__process_comm_event
    [OVERRIDE] old :1221169 new mv str mv
    [debug] deliver
    [debug] deliver
    [debug] deliver
    [debug] deliver
    [debug] deliver
    [debug] deliver
    [debug] deliver
    [debug] deliver
    [debug] deliver
    [debug] deliver
	 0.000 ( 0.013 ms): mv/1221169 renameat2(olddfd: CWD, oldname: "/tmp/file1", newdfd: CWD, newname: "/tmp/file2", flags: NOREPLACE) = 0
    [debug] deliver

    $ touch /tmp/file1 && sudo /tmp/perf trace -e renameat* -- mv /tmp/file1 /tmp/file2 && rm -f /tmp/file2
    [debug] deliver
    [debug] deliver
    [debug] deliver
    [debug] deliver
    [debug] deliver
    [debug] deliver
    [debug] deliver
	 0.000 ( 0.014 ms): :1221398/1221398 renameat2(olddfd: CWD, oldname: "/tmp/file1", newdfd: CWD, newname: "/tmp/file2", flags: NOREPLACE) = 0
    [debug] deliver
    [debug] deliver
    [debug] machine__process_comm_event
    [OVERRIDE] old :1221398 new mv str mv
    [debug] deliver
    [debug] deliver
    [debug] deliver

Anyway, use --sort-events in BTF general tests to avoid :PID, a comm is
preferred.

[1]: https://lore.kernel.org/linux-perf-users/Z_AeswETE5xLcPT8@google.com/
[2]: https://gist.githubusercontent.com/Sberm/6b72b2a1cf1c62244f1f996481769baf/raw/529667bd74a2e7e1953bbd4be545bf875da8a3e7/unsorted.patch

Signed-off-by: Howard Chu <howardchu95@...il.com>
---
 tools/perf/tests/shell/trace_btf_general.sh | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/perf/tests/shell/trace_btf_general.sh b/tools/perf/tests/shell/trace_btf_general.sh
index 5fa50d815203..30cd3a53f868 100755
--- a/tools/perf/tests/shell/trace_btf_general.sh
+++ b/tools/perf/tests/shell/trace_btf_general.sh
@@ -27,7 +27,7 @@ check_vmlinux() {
 
 trace_test_string() {
   echo "Testing perf trace's string augmentation"
-  output="$(perf trace -e renameat* --max-events=1 -- mv ${file1} ${file2} 2>&1)"
+  output="$(perf trace --sort-events -e renameat* --max-events=1 -- mv ${file1} ${file2} 2>&1)"
   if ! echo "$output" | grep -q -E "^mv/[0-9]+ renameat(2)?\(.*, \"${file1}\", .*, \"${file2}\", .*\) += +[0-9]+$"
   then
     printf "String augmentation test failed, output:\n$output\n"
@@ -38,7 +38,7 @@ trace_test_string() {
 trace_test_buffer() {
   echo "Testing perf trace's buffer augmentation"
   # echo will insert a newline (\10) at the end of the buffer
-  output="$(perf trace -e write --max-events=1 -- echo "${buffer}" 2>&1)"
+  output="$(perf trace --sort-events -e write --max-events=1 -- echo "${buffer}" 2>&1)"
   if ! echo "$output" | grep -q -E "^echo/[0-9]+ write\([0-9]+, ${buffer}.*, [0-9]+\) += +[0-9]+$"
   then
     printf "Buffer augmentation test failed, output:\n$output\n"
@@ -48,7 +48,7 @@ trace_test_buffer() {
 
 trace_test_struct_btf() {
   echo "Testing perf trace's struct augmentation"
-  output="$(perf trace -e clock_nanosleep --force-btf --max-events=1 -- sleep 1 2>&1)"
+  output="$(perf trace --sort-events -e clock_nanosleep --force-btf --max-events=1 -- sleep 1 2>&1)"
   if ! echo "$output" | grep -q -E "^sleep/[0-9]+ clock_nanosleep\(0, 0, \{1,\}, 0x[0-9a-f]+\) += +[0-9]+$"
   then
 	printf "BTF struct augmentation test failed, output:\n$output\n"
-- 
2.45.2