linux-kernel - Re: [RFC PATCH 0/5] Generic IPI sending tracepoint

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Message-ID: <xhsmhfsfufh51.mognet@vschneid.remote.csb>
Date:   Tue, 11 Oct 2022 17:40:26 +0100
From:   Valentin Schneider <vschneid@...hat.com>
To:     Daniel Bristot de Oliveira <bristot@...hat.com>
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,
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        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>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Juri Lelli <juri.lelli@...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>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Guo Ren <guoren@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Douglas RAILLARD <douglas.raillard@....com>
Subject: Re: [RFC PATCH 0/5] Generic IPI sending tracepoint

On 11/10/22 18:22, Daniel Bristot de Oliveira wrote:
> On 10/11/22 18:17, Valentin Schneider wrote:
>> Thinking out loud, it makes way more sense to record a cpumask in the
>> tracepoint, but perhaps we could have a postprocessing step to transform
>> those into N events each targeting a single CPU?
>
> My approach on the tracers/rtla is to make the simple things in kernel, and beautify
> things in user-space.
>
> You could keep the tracepoint as a mask, and then make it pretty, like cpus=3-5,8
> in user-space. For example with a trace-cmd/perf loadable plugin, libtracefs helper.
>

That's a nice idea, the one downside I see is that means registering an
event handler for all events with cpumasks rather than directly targeting
cpumask fields, but that doesn't look too horrible. I'll dig a bit in that
direction.

> For rtla I was thinking to make a new tool to parse them. and make it pretty there.
>
> -- Daniel