Re: [PATCH 4/4] tracing: Add __print_ns_to_secs() and __print_ns_without_secs() helpers

Steven Rostedt
2016-02-23T13:18:02Z

On Tue, 23 Feb 2016 13:49:15 +0100
Peter Zijlstra <peterz@infradead.org> wrote:

> On Mon, Feb 22, 2016 at 04:26:53PM -0500, Steven Rostedt wrote:
> > From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
> >
> > To have nanosecond output displayed in a more human readable format, its
> > nicer to convert it to a seconds format (XXX.YYYYYYYYY). The problem is that
> > to do so, the numbers must be divided by NSEC_PER_SEC, and moded too. But as
> > these numbers are 64 bit, this can not be done simply with '/' and '%'
> > operators, but must use do_div() instead.
>
> Would not div_[us]64_rem() make more sense? It would typically result in
> just the one division, instead of two.

The problem is, how do you do that in a printf() statement?

We have "%llu.%09ul" which is two arguments in the printf(). And the
values we are processing can't be modified. Which is why the macro uses
({ }) and creates a temp variable.

-- Steve