linux-kernel - Re: [PATCH] kselftests: ftrace: limit the executing time by reading from cached trace

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Date:   Wed, 20 Oct 2021 11:55:22 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Li Zhijian <lizhijian@...fujitsu.com>, <mingo@...hat.com>,
        <shuah@...nel.org>, <linux-kselftest@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Philip Li <philip.li@...el.com>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] kselftests: ftrace: limit the executing time by reading
 from cached trace

On Tue, 19 Oct 2021 22:34:54 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Wed, 20 Oct 2021 11:20:27 +0900
> Masami Hiramatsu <mhiramat@...nel.org> wrote:
> 
> > Hmm, by the way, shouldn't we set this feature by default?
> > There are many "cat trace | grep ..." style test code in ftracetest just for
> > checking whether the event is recorded. At least for the ftracetest, it should
> > be set unless the testcase is explicitly disable it.
> 
> For testing, sure.
> 
> I was criticized by the BPF folks about tracing stopping when the trace
> file was being read. So for normal operations, it doesn't pause, because
> that "confuses" people (so I am told).

OK, I got it.

Here is the patch to enable it by default for ftracetest :)

Thanks!

>From 61e641f494307d9942a8415bc6743e85dd95438e Mon Sep 17 00:00:00 2001
From: Masami Hiramatsu <mhiramat@...nel.org>
Date: Wed, 20 Oct 2021 11:50:35 +0900
Subject: [PATCH] selftests/ftrace: Stop tracing while reading the trace file
 by default

Stop tracing while reading the trace file by default, to prevent
the test results while checking it and to avoid taking a long time
to check the result.
If there is any testcase which wants to test the tracing while reading
the trace file, please override this setting inside the test case.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 tools/testing/selftests/ftrace/test.d/functions | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/testing/selftests/ftrace/test.d/functions b/tools/testing/selftests/ftrace/test.d/functions
index 000fd05e84b1..8adc0140d03f 100644
--- a/tools/testing/selftests/ftrace/test.d/functions
+++ b/tools/testing/selftests/ftrace/test.d/functions
@@ -124,6 +124,12 @@ initialize_ftrace() { # Reset ftrace to initial-state
     [ -f uprobe_events ] && echo > uprobe_events
     [ -f synthetic_events ] && echo > synthetic_events
     [ -f snapshot ] && echo 0 > snapshot
+
+# Stop tracing while reading the trace file by default, to prevent
+# the test results while checking it and to avoid taking a long time
+# to check the result.
+    [ -f options/pause-on-trace ] && echo 1 > options/pause-on-trace
+
     clear_trace
     enable_tracing
 }
-- 
2.25.1

 


-- 
Masami Hiramatsu <mhiramat@...nel.org>