On Fri, Dec 30, 2016 at 1:02 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Haribabu Kommi <kommi.haribabu@gmail.com> writes: > Attached a patch that replaces most of the getimeofday function calls, > except timeofday(user callable) and GetCurrentTimestamp functions.
I looked at this for awhile and could not convince myself that it's a good idea. Trying to do s/gettimeofday/clock_gettime/g is not going to do much for us except create portability headaches. According to my tests, clock_gettime is not noticeably faster than gettimeofday on any platform, except that if you use nonstandard clockids like CLOCK_REALTIME_COARSE then on *some* platforms it's a little bit quicker, at the cost of being a great deal less precise. But we'd have to research the existence and effects of nonstandard clockids on every platform. So AFAICS the only clear advantage to switching is the extra precision available from clock_gettime.
But ... most of the places you've touched in this patch have neither any need for sub-microsecond precision nor any great need to worry about shaving a few ns off the time taken by the call. As far as I can find, the only place where it's actually worth our trouble to deal with it is instr_time.h (ie, EXPLAIN ANALYZE and a few other uses).
So I think we should do something more like the attached.
Thanks for your valuable input.
As the getimeofday() function is obsolete and any further enhancements
may happen to clock_gettime() function only, because of this reason, I changed
it many places.
Yes, I agree that until unless the clock_gettime() function that performs faster
in all platforms compared to gettimeofday(), we can retain the getimeofday()
