linux-kernel - Re: [PATCH 1/2] tracing: show size of requested buffer

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Message-ID: <20211007092358.65152792@gandalf.local.home>
Date:   Thu, 7 Oct 2021 09:23:58 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     "Robin H. Johnson" <robbat2@...too.org>,
        linux-kernel@...r.kernel.org, mingo@...hat.com,
        rjohnson@...italocean.com,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH 1/2] tracing: show size of requested buffer

On Thu, 7 Oct 2021 09:11:51 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> > > +++ b/kernel/trace/trace_event_perf.c
> > > @@ -400,7 +400,8 @@ void *perf_trace_buf_alloc(int size, struct pt_regs **regs, int *rctxp)
> > >  	BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
> > >  
> > >  	if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
> > > -		      "perf buffer not large enough"))
> > > +		      "perf buffer not large enough, wanted %d, have %d",
> > > +		      size, PERF_MAX_TRACE_SIZE))  
> 
> Priting a constant seems daft.. why is any of this important in any way?

I see your point, but it can be useful if you changed it, and want to know
if you are running the kernel with the change or not.

I've done daft things were I changed a const and was running a kernel
without the change and couldn't understand why it wasn't working ;-)

-- Steve