linux-kernel - Re: [RFC PATCH 46/86] tracing: handle lazy resched

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Message-ID: <20231107191953.6b44790b@gandalf.local.home>
Date:   Tue, 7 Nov 2023 19:19:53 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Ankur Arora <ankur.a.arora@...cle.com>
Cc:     linux-kernel@...r.kernel.org, tglx@...utronix.de,
        peterz@...radead.org, torvalds@...ux-foundation.org,
        paulmck@...nel.org, linux-mm@...ck.org, x86@...nel.org,
        akpm@...ux-foundation.org, luto@...nel.org, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, mingo@...hat.com,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        willy@...radead.org, mgorman@...e.de, jon.grimm@....com,
        bharata@....com, raghavendra.kt@....com,
        boris.ostrovsky@...cle.com, konrad.wilk@...cle.com,
        jgross@...e.com, andrew.cooper3@...rix.com, mingo@...nel.org,
        bristot@...nel.org, mathieu.desnoyers@...icios.com,
        geert@...ux-m68k.org, glaubitz@...sik.fu-berlin.de,
        anton.ivanov@...bridgegreys.com, mattst88@...il.com,
        krypton@...ich-teichert.org, David.Laight@...LAB.COM,
        richard@....at, mjguzik@...il.com,
        Richard Henderson <richard.henderson@...aro.org>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>, linux-alpha@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-m68k@...ts.linux-m68k.org, Dinh Nguyen <dinguyen@...nel.org>
Subject: Re: [RFC PATCH 46/86] tracing: handle lazy resched

On Tue,  7 Nov 2023 13:57:32 -0800
Ankur Arora <ankur.a.arora@...cle.com> wrote:

> Tracing support.
> 
> Note: this is quite incomplete.

What's not complete? The removal of the IRQS_NOSUPPORT?

Really, that's only for alpha, m68k and nios2. I think setting 'X' is not
needed anymore, and we can use that bit for this, and for those archs, have
0 for interrupts disabled.

-- Steve


> 
> Originally-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
> ---
>  include/linux/trace_events.h |  6 +++---
>  kernel/trace/trace.c         |  2 ++
>  kernel/trace/trace_output.c  | 16 ++++++++++++++--
>  3 files changed, 19 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
> index 21ae37e49319..355d25d5e398 100644
> --- a/include/linux/trace_events.h
> +++ b/include/linux/trace_events.h
> @@ -178,7 +178,7 @@ unsigned int tracing_gen_ctx_irq_test(unsigned int irqs_status);
>  
>  enum trace_flag_type {
>  	TRACE_FLAG_IRQS_OFF		= 0x01,
> -	TRACE_FLAG_IRQS_NOSUPPORT	= 0x02,
> +	TRACE_FLAG_NEED_RESCHED_LAZY    = 0x02,
>  	TRACE_FLAG_NEED_RESCHED		= 0x04,
>  	TRACE_FLAG_HARDIRQ		= 0x08,
>  	TRACE_FLAG_SOFTIRQ		= 0x10,
> @@ -205,11 +205,11 @@ static inline unsigned int tracing_gen_ctx(void)
>  
>  static inline unsigned int tracing_gen_ctx_flags(unsigned long irqflags)
>  {
> -	return tracing_gen_ctx_irq_test(TRACE_FLAG_IRQS_NOSUPPORT);
> +	return tracing_gen_ctx_irq_test(0);
>  }
>  static inline unsigned int tracing_gen_ctx(void)
>  {
> -	return tracing_gen_ctx_irq_test(TRACE_FLAG_IRQS_NOSUPPORT);
> +	return tracing_gen_ctx_irq_test(0);
>  }
>  #endif
>  
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 7f067ad9cf50..0776dba32c2d 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -2722,6 +2722,8 @@ unsigned int tracing_gen_ctx_irq_test(unsigned int irqs_status)
>  
>  	if (tif_need_resched(RESCHED_eager))
>  		trace_flags |= TRACE_FLAG_NEED_RESCHED;
> +	if (tif_need_resched(RESCHED_lazy))
> +		trace_flags |= TRACE_FLAG_NEED_RESCHED_LAZY;
>  	if (test_preempt_need_resched())
>  		trace_flags |= TRACE_FLAG_PREEMPT_RESCHED;
>  	return (trace_flags << 16) | (min_t(unsigned int, pc & 0xff, 0xf)) |
> diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
> index db575094c498..c251a44ad8ac 100644
> --- a/kernel/trace/trace_output.c
> +++ b/kernel/trace/trace_output.c
> @@ -460,17 +460,29 @@ int trace_print_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
>  		(entry->flags & TRACE_FLAG_IRQS_OFF && bh_off) ? 'D' :
>  		(entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' :
>  		bh_off ? 'b' :
> -		(entry->flags & TRACE_FLAG_IRQS_NOSUPPORT) ? 'X' :
> +		!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_NEED_RESCHED_LAZY:
> +		need_resched = 'l';
> +		break;
>  	case TRACE_FLAG_PREEMPT_RESCHED:
>  		need_resched = 'p';
>  		break;