linux-kernel - Re: [PATCH 3/4] ring-buffer: add total count in ring-buffer-benchmark

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Date:	Fri, 8 May 2009 06:52:39 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH 3/4] ring-buffer: add total count in
 ring-buffer-benchmark


On Thu, 7 May 2009, Andrew Morton wrote:

> On Fri, 08 May 2009 00:32:53 -0400 Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> > --- a/kernel/trace/ring_buffer_benchmark.c
> > +++ b/kernel/trace/ring_buffer_benchmark.c
> > @@ -285,6 +285,17 @@ static void ring_buffer_producer(void)
> >  		avg = 1000000 / hit;
> >  		pr_info("%ld ns per entry\n", avg);
> >  	}
> > +
> > +
> 
> s/\n\n/\n/

My pinky must hae been itchy, and hit the enter twice.

> 
> > +	if (missed) {
> > +		if (time)
> > +			missed /= (long)time;
> > +
> > +		pr_info("Total iterations per millisec: %ld\n", hit + missed);
> > +
> > +		avg = 1000000 / (hit + missed);
> 
> s/1000000/USEC_PER_SEC/?

Heh, after I sent out the patch, I noticed that number, and thought to 
myself, "oh no, akpm is going to commont on that" ;-)

> 
> Hopefully we can't have hit+missed==0.
> 
> They're counters and hence should have unsigned types.
> 
> But even unsigned up-counters can add to zero if wrapping occurs.

Eigad! I never thought about an overflow to zero. Will fix.

Thanks!

-- Steve

> 
> 
> > +		pr_info("%ld ns per entry\n", avg);
> > +	}
> >  }
> 
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