Greg Smith <g...@2ndquadrant.com> writes: > Tom Lane wrote: >> You've got a machine where gettimeofday() is really slow. This is >> common on cheap PC hardware :-(
> I'd be curious to know more about the hardware and operating system > Szymon is using if you suspect this is the case. I keep hearing about > systems where this is slow, but despite claims that they're common I've > never actually seen one. Well, they're not as common as they used to be. My understanding is that there are two independent issues: * If you have to call into the kernel to read the RTC, you're already hurting. Modern Unixen avoid this, but I think I've read that it's generally only fixed on x86_64 hardware not i386. * The original specs for reading the RTC on PC hardware did not foresee the desire of being able to read it out in a small fraction of a microsecond. I don't know the details on this exactly, but some googling turned up this: http://linux.derkeiler.com/Mailing-Lists/Kernel/2006-07/msg07415.html The OP's example involved almost 21 seconds added by approximately 2*10000000 gettimeofday probes, or right about 1 microsecond per probe... regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
