2023-07-26 12:41:56

by Ze Gao

Subject: [RFC PATCH v2 3/3] libtraceevent: use the new prev_state_char instead in tracepoint sched_switch

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

Signed-off-by: Ze Gao <[email protected]>
---
plugins/plugin_sched_switch.c | 29 ++++-------------------------
1 file changed, 4 insertions(+), 25 deletions(-)

diff --git a/plugins/plugin_sched_switch.c b/plugins/plugin_sched_switch.c
index 8752cae..5dbdc28 100644
--- a/plugins/plugin_sched_switch.c
+++ b/plugins/plugin_sched_switch.c
@@ -9,27 +9,6 @@
#include "event-parse.h"
#include "trace-seq.h"

-static void write_state(struct trace_seq *s, int val)
-{
- const char states[] = "SDTtZXxW";
- int found = 0;
- int i;
-
- for (i = 0; i < (sizeof(states) - 1); i++) {
- if (!(val & (1 << i)))
- continue;
-
- if (found)
- trace_seq_putc(s, '|');
-
- found = 1;
- trace_seq_putc(s, states[i]);
- }
-
- if (!found)
- trace_seq_putc(s, 'R');
-}
-
static void write_and_save_comm(struct tep_format_field *field,
struct tep_record *record,
struct trace_seq *s, int pid)
@@ -97,10 +76,10 @@ static int sched_switch_handler(struct trace_seq *s,
trace_seq_printf(s, "%lld ", val);

if (tep_get_field_val(s, event, "prev_prio", record, &val, 1) == 0)
- trace_seq_printf(s, "[%d] ", (int) val);
+ trace_seq_printf(s, "[%d] ", (short) val);

- if (tep_get_field_val(s, event, "prev_state", record, &val, 1) == 0)
- write_state(s, val);
+ if (tep_get_field_val(s, event, "prev_state_char", record, &val, 1) == 0)
+ trace_seq_putc(s, (char) val);

trace_seq_puts(s, " ==> ");

@@ -115,7 +94,7 @@ static int sched_switch_handler(struct trace_seq *s,
trace_seq_printf(s, "%lld", val);

if (tep_get_field_val(s, event, "next_prio", record, &val, 1) == 0)
- trace_seq_printf(s, " [%d]", (int) val);
+ trace_seq_printf(s, " [%d]", (short) val);

return 0;
}
--
2.40.1

2023-07-31 16:35:34

by Steven Rostedt

Subject: Re: [RFC PATCH v2 3/3] libtraceevent: use the new prev_state_char instead in tracepoint sched_switch

On Wed, 26 Jul 2023 20:16:18 +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 switch to use
> that instead to spare from knowing internal implementations
> in kernel.

This needs to be changed to check if the "prev_state_char" field exists,
and if not, then it must use the old method. Same for perf. The tools must
work with older kernels.

-- Steve

>
> Signed-off-by: Ze Gao <[email protected]>
> ---
> plugins/plugin_sched_switch.c | 29 ++++-------------------------
> 1 file changed, 4 insertions(+), 25 deletions(-)
>
> diff --git a/plugins/plugin_sched_switch.c b/plugins/plugin_sched_switch.c
> index 8752cae..5dbdc28 100644
> --- a/plugins/plugin_sched_switch.c
> +++ b/plugins/plugin_sched_switch.c
> @@ -9,27 +9,6 @@
> #include "event-parse.h"
> #include "trace-seq.h"
>
> -static void write_state(struct trace_seq *s, int val)
> -{
> - const char states[] = "SDTtZXxW";
> - int found = 0;
> - int i;
> -
> - for (i = 0; i < (sizeof(states) - 1); i++) {
> - if (!(val & (1 << i)))
> - continue;
> -
> - if (found)
> - trace_seq_putc(s, '|');
> -
> - found = 1;
> - trace_seq_putc(s, states[i]);
> - }
> -
> - if (!found)
> - trace_seq_putc(s, 'R');
> -}
> -
> static void write_and_save_comm(struct tep_format_field *field,
> struct tep_record *record,
> struct trace_seq *s, int pid)
> @@ -97,10 +76,10 @@ static int sched_switch_handler(struct trace_seq *s,
> trace_seq_printf(s, "%lld ", val);
>
> if (tep_get_field_val(s, event, "prev_prio", record, &val, 1) ==
> 0)
> - trace_seq_printf(s, "[%d] ", (int) val);
> + trace_seq_printf(s, "[%d] ", (short) val);
>
> - if (tep_get_field_val(s, event, "prev_state", record, &val, 1)
> == 0)
> - write_state(s, val);
> + if (tep_get_field_val(s, event, "prev_state_char", record,
> &val, 1) == 0)
> + trace_seq_putc(s, (char) val);
>
> trace_seq_puts(s, " ==> ");
>
> @@ -115,7 +94,7 @@ static int sched_switch_handler(struct trace_seq *s,
> trace_seq_printf(s, "%lld", val);
>
> if (tep_get_field_val(s, event, "next_prio", record, &val, 1) ==
> 0)
> - trace_seq_printf(s, " [%d]", (int) val);
> + trace_seq_printf(s, " [%d]", (short) val);
>
> return 0;
> }

2023-08-01 02:14:02

by Ze Gao

Subject: Re: [RFC PATCH v2 3/3] libtraceevent: use the new prev_state_char instead in tracepoint sched_switch

Roger that!

Thanks,
Ze

On Mon, Jul 31, 2023 at 11:40 PM Steven Rostedt <[email protected]> wrote:
>
> On Wed, 26 Jul 2023 20:16:18 +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 switch to use
> > that instead to spare from knowing internal implementations
> > in kernel.
>
> This needs to be changed to check if the "prev_state_char" field exists,
> and if not, then it must use the old method. Same for perf. The tools must
> work with older kernels.
>
> -- Steve
>
> >
> > Signed-off-by: Ze Gao <[email protected]>
> > ---
> > plugins/plugin_sched_switch.c | 29 ++++-------------------------
> > 1 file changed, 4 insertions(+), 25 deletions(-)
> >
> > diff --git a/plugins/plugin_sched_switch.c b/plugins/plugin_sched_switch.c
> > index 8752cae..5dbdc28 100644
> > --- a/plugins/plugin_sched_switch.c
> > +++ b/plugins/plugin_sched_switch.c
> > @@ -9,27 +9,6 @@
> > #include "event-parse.h"
> > #include "trace-seq.h"
> >
> > -static void write_state(struct trace_seq *s, int val)
> > -{
> > - const char states[] = "SDTtZXxW";
> > - int found = 0;
> > - int i;
> > -
> > - for (i = 0; i < (sizeof(states) - 1); i++) {
> > - if (!(val & (1 << i)))
> > - continue;
> > -
> > - if (found)
> > - trace_seq_putc(s, '|');
> > -
> > - found = 1;
> > - trace_seq_putc(s, states[i]);
> > - }
> > -
> > - if (!found)
> > - trace_seq_putc(s, 'R');
> > -}
> > -
> > static void write_and_save_comm(struct tep_format_field *field,
> > struct tep_record *record,
> > struct trace_seq *s, int pid)
> > @@ -97,10 +76,10 @@ static int sched_switch_handler(struct trace_seq *s,
> > trace_seq_printf(s, "%lld ", val);
> >
> > if (tep_get_field_val(s, event, "prev_prio", record, &val, 1) ==
> > 0)
> > - trace_seq_printf(s, "[%d] ", (int) val);
> > + trace_seq_printf(s, "[%d] ", (short) val);
> >
> > - if (tep_get_field_val(s, event, "prev_state", record, &val, 1)
> > == 0)
> > - write_state(s, val);
> > + if (tep_get_field_val(s, event, "prev_state_char", record,
> > &val, 1) == 0)
> > + trace_seq_putc(s, (char) val);
> >
> > trace_seq_puts(s, " ==> ");
> >
> > @@ -115,7 +94,7 @@ static int sched_switch_handler(struct trace_seq *s,
> > trace_seq_printf(s, "%lld", val);
> >
> > if (tep_get_field_val(s, event, "next_prio", record, &val, 1) ==
> > 0)
> > - trace_seq_printf(s, " [%d]", (int) val);
> > + trace_seq_printf(s, " [%d]", (short) val);
> >
> > return 0;
> > }
>