Messages in this thread | | | Date | Tue, 23 Feb 2016 15:01:43 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 4/4] tracing: Add __print_ns_to_secs() and __print_ns_without_secs() helpers |
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On Tue, Feb 23, 2016 at 08:17:57AM -0500, Steven Rostedt wrote: > 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.
Hurm,. yes that's not something easily done. We need a temporary limited in scope to the printf statement, and C doesn't really do that.
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