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

[Peter Zijlstra]

On Tue, Sep 07, 2021 at 09:24:26PM -0400, Steven Rostedt wrote:
> 
> I'll need Acks for these patches from the Perf maintainers.
> 
> -- Steve
> 
> 
> On Mon, 30 Aug 2021 21:37:22 -0700
> "Robin H. Johnson" <robbat2@xxxxxxxxxx> wrote:
> 
> > If the perf buffer isn't large enough, provide a hint about how large it
> > needs to be for whatever is running.

Is that an actual reason?

> > Signed-off-by: Robin H. Johnson <robbat2@xxxxxxxxxx>
> > ---
> >  kernel/trace/trace_event_perf.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
> > index 03be4435d103..26eed4b89100 100644
> > --- a/kernel/trace/trace_event_perf.c
> > +++ 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?