linux-kernel - Re: [RFC PATCH 4/5] irq_work: Trace calls to arch_irq_work

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Date:   Tue, 11 Oct 2022 16:02:06 +0100
From:   Valentin Schneider <vschneid@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-alpha@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org,
        linux-hexagon@...r.kernel.org, linux-ia64@...r.kernel.org,
        loongarch@...ts.linux.dev, linux-mips@...r.kernel.org,
        openrisc@...ts.librecores.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
        x86@...nel.org, "Paul E. McKenney" <paulmck@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Juri Lelli <juri.lelli@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Nicholas Piggin <npiggin@...il.com>,
        Guo Ren <guoren@...nel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [RFC PATCH 4/5] irq_work: Trace calls to arch_irq_work_raise()

On 08/10/22 15:34, Steven Rostedt wrote:
> On Fri,  7 Oct 2022 16:45:32 +0100
> Valentin Schneider <vschneid@...hat.com> wrote:
>>  }
>>  
>> +static inline void irq_work_raise(void)
>> +{
>> +	if (arch_irq_work_has_interrupt())
>> +		trace_ipi_send_cpu(_RET_IP_, smp_processor_id());
>
> To save on the branch, let's make the above:
>
> 	if (trace_ipi_send_cpu_enabled() && arch_irq_work_has_interrupt())
>
> As the "trace_*_enabled()" is a static branch that will make it a nop
> when the tracepoint is not enabled.
>

Makes sense, thanks for the suggestion.

> -- Steve
>
>
>> +
>> +	arch_irq_work_raise();
>> +}
>> +
>>  /* Enqueue on current CPU, work must already be claimed and preempt disabled */