linux-kernel - Re: [RFC PATCH 1/1] smp: Add tracepoints for functions called with smp_call

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Message-ID: <20230504150113.GB1744142@hirez.programming.kicks-ass.net>
Date:   Thu, 4 May 2023 17:01:13 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Valentin Schneider <vschneid@...hat.com>
Cc:     Leonardo Brás <leobras@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yury Norov <yury.norov@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Nadav Amit <namit@...are.com>,
        Zhen Lei <thunder.leizhen@...wei.com>,
        Chen Zhongjin <chenzhongjin@...wei.com>,
        linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...nel.org>
Subject: Re: [RFC PATCH 1/1] smp: Add tracepoints for functions called with
 smp_call_function*()

On Thu, May 04, 2023 at 12:59:41PM +0100, Valentin Schneider wrote:

> With that said, I suppose this could still be helpful for e.g. osnoise to
> hook into and point the finger at which CPU/context sent the problematic
> IPI. Or more generally, as Leonardo suggested, to measure CSD IPI delivery
> times.
> 
> One thing though is that trace_ipi_send_cpu*() is not used solely for
> CSD's, cf. irq_work_raise() or smp_send_reschedule(). We might want to
> split that into e.g. trace_csd_queue_cpu*() + trace_ipi_send*().
> 
> Something like so...
> 

Yeah, looks about right I suppose.. it generates more events, but given
we need the csd that's inevitable.