2023-08-02 13:32:03

by Ze Gao

Subject: [RFC PATCH v4 7/7] libtraceevent: prefer to use prev_state_char introduced in sched_switch

Since the sched_switch tracepoint introduces a new variable to
report sched-out task state in symbolic char, we prefer to use
it to spare from knowing internal implementations in kernel.

Also we keep the old parsing logic intact but sync the state char
array with the latest kernel.

Signed-off-by: Ze Gao <[email protected]>
---
plugins/plugin_sched_switch.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/plugins/plugin_sched_switch.c b/plugins/plugin_sched_switch.c
index e0986ac..4c57322 100644
--- a/plugins/plugin_sched_switch.c
+++ b/plugins/plugin_sched_switch.c
@@ -11,7 +11,7 @@

static void write_state(struct trace_seq *s, int val)
{
- const char states[] = "SDTtXZPI";
+ const char states[] = "SDTtXZPIp";
int found = 0;
int i;

@@ -99,7 +99,12 @@ static int sched_switch_handler(struct trace_seq *s,
if (tep_get_field_val(s, event, "prev_prio", record, &val, 1) == 0)
trace_seq_printf(s, "[%d] ", (int) val);

- if (tep_get_field_val(s, event, "prev_state", record, &val, 1) == 0)
+ //find if has prev_state_char, otherwise fallback to prev_state
+ if (tep_find_field(event, "prev_state_char")) {
+ if (tep_get_field_val(s, event, "prev_state_char", record, &val, 1) == 0)
+ trace_seq_putc(s, (char) val);
+ }
+ else if (tep_get_field_val(s, event, "prev_state", record, &val, 1) == 0)
write_state(s, val);

trace_seq_puts(s, " ==> ");
--
2.41.0

2023-08-02 15:16:35

by Steven Rostedt

Subject: Re: [RFC PATCH v4 7/7] libtraceevent: prefer to use prev_state_char introduced in sched_switch

On Wed, 2 Aug 2023 08:10:02 -0400
Ze Gao <[email protected]> wrote:

> Since the sched_switch tracepoint introduces a new variable to
> report sched-out task state in symbolic char, we prefer to use
> it to spare from knowing internal implementations in kernel.
>
> Also we keep the old parsing logic intact but sync the state char
> array with the latest kernel.
>

This should also go to [email protected].

> Signed-off-by: Ze Gao <[email protected]>
> ---
> plugins/plugin_sched_switch.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/plugins/plugin_sched_switch.c b/plugins/plugin_sched_switch.c
> index e0986ac..4c57322 100644
> --- a/plugins/plugin_sched_switch.c
> +++ b/plugins/plugin_sched_switch.c
> @@ -11,7 +11,7 @@
>
> static void write_state(struct trace_seq *s, int val)
> {
> - const char states[] = "SDTtXZPI";
> + const char states[] = "SDTtXZPIp";
> int found = 0;
> int i;
>
> @@ -99,7 +99,12 @@ static int sched_switch_handler(struct trace_seq *s,
> if (tep_get_field_val(s, event, "prev_prio", record, &val, 1) == 0)
> trace_seq_printf(s, "[%d] ", (int) val);
>
> - if (tep_get_field_val(s, event, "prev_state", record, &val, 1) == 0)
> + //find if has prev_state_char, otherwise fallback to prev_state

Use standard C comment notation "/* ... */"

> + if (tep_find_field(event, "prev_state_char")) {
> + if (tep_get_field_val(s, event, "prev_state_char", record, &val, 1) == 0)
> + trace_seq_putc(s, (char) val);
> + }
> + else if (tep_get_field_val(s, event, "prev_state", record, &val, 1) == 0)

This should be:

} else if (..) {

> write_state(s, val);

}

-- Steve

>
> trace_seq_puts(s, " ==> ");