Re: [PATCH] perf ftrace: Make system wide the default target for latency subcommand
From: Yang Jihong
Date: Fri Mar 24 2023 - 23:29:13 EST
Hello,
On 2023/3/25 9:39, Namhyung Kim wrote:
Hello,
On Thu, Mar 23, 2023 at 8:29 PM Yang Jihong <yangjihong1@xxxxxxxxxx> wrote:
If no target is specified for 'latency' subcommand, the execution fails
because - 1 (invalid value) is written to set_ftrace_pid tracefs file.
Make system wide the default target, which is the same as the default
behavior of 'trace' subcommand.
I followed the convention to use -a for system-wide profiling.
Not sure if it's ok to make it default, but I don't object. :)
Thanks for the reply.
Yes, "perf ftrace latency" supports -a for system wide profiles.
Because "perf ftrace trace" defaults to system wide when no target is
specified. Therefore, I sent the patch to check whether "latency" is
consistent with the behavior of the "trace". :)
Thanks,
Yang.
Thanks,
Namhyung
Before the fix:
# perf ftrace latency -T schedule
failed to set ftrace pid
After the fix:
# perf ftrace latency -T schedule
^C# DURATION | COUNT | GRAPH |
0 - 1 us | 0 | |
1 - 2 us | 0 | |
2 - 4 us | 0 | |
4 - 8 us | 2828 | #### |
8 - 16 us | 23953 | ######################################## |
16 - 32 us | 408 | |
32 - 64 us | 318 | |
64 - 128 us | 4 | |
128 - 256 us | 3 | |
256 - 512 us | 0 | |
512 - 1024 us | 1 | |
1 - 2 ms | 4 | |
2 - 4 ms | 0 | |
4 - 8 ms | 0 | |
8 - 16 ms | 0 | |
16 - 32 ms | 0 | |
32 - 64 ms | 0 | |
64 - 128 ms | 0 | |
128 - 256 ms | 4 | |
256 - 512 ms | 2 | |
512 - 1024 ms | 0 | |
1 - ... s | 0 | |
Fixes: 53be50282269 ("perf ftrace: Add 'latency' subcommand")
Signed-off-by: Yang Jihong <yangjihong1@xxxxxxxxxx>
---
tools/perf/builtin-ftrace.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index d7fe00f66b83..fb1b66ef2e16 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -1228,10 +1228,12 @@ int cmd_ftrace(int argc, const char **argv)
goto out_delete_filters;
}
+ /* Make system wide (-a) the default target. */
+ if (!argc && target__none(&ftrace.target))
+ ftrace.target.system_wide = true;
+
switch (subcmd) {
case PERF_FTRACE_TRACE:
- if (!argc && target__none(&ftrace.target))
- ftrace.target.system_wide = true;
cmd_func = __cmd_ftrace;
break;
case PERF_FTRACE_LATENCY:
--
2.30.GIT
.