Fastest way to get local time in unix

Question

I am investigating logging performance on unix system. Thing is I found that the most expensive operation is obtaining date.

Currently I am getting time like this -

timeb currTime;
struct tm localTime;
ftime( &currTime )
localtime_r(&currTime.time, &localTime);

I changed it to

struct timeval tv;
gettimeofday(&tv, NULL); 
time_t curtime = tv.tv_sec;
struct tm localTime = *(localtime(&curtime));

and did not see any performance improvement. So I am wondering maybe this is not the fastest way to get local time on unix systems?

Please, share you thoughts about that.

Thanks on advance.

Answer 1

gettimeofday gives you the UTC time very quickly. Converting to local time is not so quick.

Defer converting that to local time until you are off the performance critical path.

Also you can cache the UTC to local time conversion factor once a day to speed up the conversion to local time, although this is not perfect it is probably good enough for logging purposes.