linux-kernel - Re: [PATCH 2/3] tracing: Record task flag NEED_RESCHED

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Message-ID: <87iku1b2vf.fsf@oracle.com>
Date: Wed, 09 Oct 2024 10:30:28 -0700
From: Ankur Arora <ankur.a.arora@...cle.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Peter
 Zijlstra <peterz@...radead.org>, tglx@...utronix.de,
        mingo@...nel.org, juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, vschneid@...hat.com, ankur.a.arora@...cle.com,
        efault@....de, Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH 2/3] tracing: Record task flag NEED_RESCHED_LAZY.


Sebastian Andrzej Siewior <bigeasy@...utronix.de> writes:

> The scheduler added NEED_RESCHED_LAZY scheduling. Record this state as
> part of trace flags and expose it in the need_resched field.
>
> Record and expose NEED_RESCHED_LAZY.
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
>  include/linux/trace_events.h |  1 +
>  kernel/trace/trace.c         |  2 ++
>  kernel/trace/trace_output.c  | 14 +++++++++++++-
>  3 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
> index d5c0fcf20f024..4cae6f2581379 100644
> --- a/include/linux/trace_events.h
> +++ b/include/linux/trace_events.h
> @@ -185,6 +185,7 @@ unsigned int tracing_gen_ctx_irq_test(unsigned int irqs_status);
>  enum trace_flag_type {
>  	TRACE_FLAG_IRQS_OFF		= 0x01,
>  	TRACE_FLAG_NEED_RESCHED		= 0x02,
> +	TRACE_FLAG_NEED_RESCHED_LAZY	= 0x04,
>  	TRACE_FLAG_HARDIRQ		= 0x08,
>  	TRACE_FLAG_SOFTIRQ		= 0x10,
>  	TRACE_FLAG_PREEMPT_RESCHED	= 0x20,
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 1c69ca1f10886..29d7703751aa9 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -2544,6 +2544,8 @@ unsigned int tracing_gen_ctx_irq_test(unsigned int irqs_status)
>  		trace_flags |= TRACE_FLAG_NEED_RESCHED;
>  	if (test_preempt_need_resched())
>  		trace_flags |= TRACE_FLAG_PREEMPT_RESCHED;
> +	if (tif_test_bit(TIF_NEED_RESCHED_LAZY))

TIF_NEED_RESCHED_LAZY falls back to TIF_NEED_RESCHED without
CONFIG_ARCH_HAS_PREEMPT_LAZY. So, you might need to add an explicit
check for that as well.

With that,
 Reviewed-by: Ankur Arora <ankur.a.arora@...cle.com>

Ankur

> +		trace_flags |= TRACE_FLAG_NEED_RESCHED_LAZY;
>  	return (trace_flags << 16) | (min_t(unsigned int, pc & 0xff, 0xf)) |
>  		(min_t(unsigned int, migration_disable_value(), 0xf)) << 4;
>  }
> diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
> index 829daa0764dd9..23ca2155306b1 100644
> --- a/kernel/trace/trace_output.c
> +++ b/kernel/trace/trace_output.c
> @@ -463,17 +463,29 @@ int trace_print_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
>  		!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_SUPPORT) ? 'X' :
>  		'.';
>
> -	switch (entry->flags & (TRACE_FLAG_NEED_RESCHED |
> +	switch (entry->flags & (TRACE_FLAG_NEED_RESCHED | TRACE_FLAG_NEED_RESCHED_LAZY |
>  				TRACE_FLAG_PREEMPT_RESCHED)) {
> +	case TRACE_FLAG_NEED_RESCHED | TRACE_FLAG_NEED_RESCHED_LAZY | TRACE_FLAG_PREEMPT_RESCHED:
> +		need_resched = 'B';
> +		break;
>  	case TRACE_FLAG_NEED_RESCHED | TRACE_FLAG_PREEMPT_RESCHED:
>  		need_resched = 'N';
>  		break;
> +	case TRACE_FLAG_NEED_RESCHED_LAZY | TRACE_FLAG_PREEMPT_RESCHED:
> +		need_resched = 'L';
> +		break;
> +	case TRACE_FLAG_NEED_RESCHED | TRACE_FLAG_NEED_RESCHED_LAZY:
> +		need_resched = 'b';
> +		break;
>  	case TRACE_FLAG_NEED_RESCHED:
>  		need_resched = 'n';
>  		break;
>  	case TRACE_FLAG_PREEMPT_RESCHED:
>  		need_resched = 'p';
>  		break;
> +	case TRACE_FLAG_NEED_RESCHED_LAZY:
> +		need_resched = 'l';
> +		break;
>  	default:
>  		need_resched = '.';
>  		break;


--
ankur