On 3/2/18 3:49 PM, Dave Chinner wrote: > On Thu, Mar 01, 2018 at 10:00:52PM -0600, Eric Sandeen wrote: >> On 2/28/18 9:56 PM, Dave Chinner wrote: >>> From: Dave Chinner <dchinner@xxxxxxxxxx> >>> >>> CUrrently the 100th/sec units always report zero, such as: >>> >>> 32 MiB, 8192 ops; 0:00:21.00 (1.476 MiB/sec and 377.9260 ops/sec) >>> ^^ >>> >>> This is incorrect. Fix the maths that is wrong by removing all the >>> unnecesary floating point maths and just using basic integer >>> division... >>> >>> Signed-Off-By: Dave Chinner <dchinner@xxxxxxxxxx> >>> --- >>> libxcmd/input.c | 16 ++++++++-------- >>> 1 file changed, 8 insertions(+), 8 deletions(-) >>> >>> diff --git a/libxcmd/input.c b/libxcmd/input.c >>> index 441bb2fbbf34..6e7a8c9822ee 100644 >>> --- a/libxcmd/input.c >>> +++ b/libxcmd/input.c >>> @@ -154,9 +154,10 @@ tdiv(double value, struct timeval tv) >>> return value / ((double)tv.tv_sec + ((double)tv.tv_usec / 1000000.0)); >>> } >>> >>> -#define HOURS(sec) ((sec) / (60 * 60)) >>> -#define MINUTES(sec) (((sec) % (60 * 60)) / 60) >>> -#define SECONDS(sec) ((sec) % 60) >>> +#define HOURS(sec) ((sec) / (60 * 60)) >>> +#define MINUTES(sec) (((sec) % (60 * 60)) / 60) >>> +#define SECONDS(sec) ((sec) % 60) >>> +#define USEC_TO_100THS(usec) ((usec) / 1000 / 10) >> >> I guess this works but I expected to convert "microseconds to 100ths" >> via a conversion like: >> >> usec * 1sec/1000000usec * 100 hundredths/1sec > > That's what the old code tried to do with floating point math and > casts, but that didn't work. > >> so just for readability I'd have expected: >> >> #define USEC_TO_100THS(usec) ((usec) / 1000000 * 100) > > Welcome to Integer Math 101: Integer Division. You'll always get > zero, because N / M = 0 when N < M. hm, right. >> or possibly just >> #define USEC_TO_100THS(usec) ((usec) / 10000) >> >> ... I'm confused by your choice of orders of magnitude above even >> though it works - it seems a bit random to divide it that way, >> unless I'm missing something? >> >> (I had a physics teacher who drilled THINK UNITS BEFORE YOU THINK >> NUMBERS" into my head an I still do) :) > > Yeah, I did. I did us->ms first, then ms->100ths. i.e.: > > milliseconds = usec / 1000 > hundreths = ms / 10. > > This should be obvious to anyone who uses the metric system for > units of measurement. I see what you did there! ok. Well, whatever. I can merge it as is if you like, and hope the next person to read it is smarter than I am. Shouldn't be hard. -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
