2023-08-01 10:16:53

by Ze Gao

Subject: [RFC PATCH v3 6/6] 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 8752cae..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[] = "SDTtZXxW";
+ 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, " ==> ");
--
2.40.1

2023-08-01 15:27:13

by Steven Rostedt

Subject: Re: [RFC PATCH v3 6/6] libtraceevent: prefer to use prev_state_char introduced in sched_switch

On Tue, 1 Aug 2023 17:01:24 +0800
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 be two patches. First sync the state char array and then add
your state_char change. The two changes are agnostic to each other, and
should be separate commits. Same goes for the perf changes.

-- Steve


>
> 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 8752cae..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[] = "SDTtZXxW";
> + 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, " ==> ");

2023-08-02 03:34:10

by Ze Gao

Subject: Re: [RFC PATCH v3 6/6] libtraceevent: prefer to use prev_state_char introduced in sched_switch

Fair enough! Already did this in perf fixes. Will push a v4
to do this.

Thanks,
Ze


On Tue, Aug 1, 2023 at 10:19 PM Steven Rostedt <[email protected]> wrote:
>
> On Tue, 1 Aug 2023 17:01:24 +0800
> 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 be two patches. First sync the state char array and then add
> your state_char change. The two changes are agnostic to each other, and
> should be separate commits. Same goes for the perf changes.
>
> -- Steve
>
>
> >
> > 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 8752cae..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[] = "SDTtZXxW";
> > + 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, " ==> ");
>