On 2016-02-16 09:13:09 +0100, Andres Freund wrote: > What we do we think the resolution is on modern > >systems? I would not have guessed that to be inaccurate. > > Depends in a lot of factors. The biggest being how busy you're system > is. On an mostly idle system (i.e. workout so CPUs being > overcommitted) you can get resolutions considerably below one > millisecond. HPET can get you very low latencies, making OS scheduling > latencies the dominant factor, but one that can be tuned.
To back up my claim on this, read man 7 time (e.g. http://linux.die.net/man/7/time), especially "The software clock, HZ, and jiffies" and "High-resolution timers". To quote the most salient point: > Before Linux 2.6.21, the accuracy of timer and sleep system calls (see > below) was also limited by the size of the jiffy. > > Since Linux 2.6.21, Linux supports high-resolution timers (HRTs), > optionally configurable via CONFIG_HIGH_RES_TIMERS. On a system that > supports HRTs, the accuracy of sleep and timer system calls is no longer > constrained by the jiffy, but instead can be as accurate as the hardware > allows (microsecond accuracy is typical of modern hardware). Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
