* Tom Lane: > On Linux (RHEL6, 2.4GHz x86_64), I find that gettimeofday(), > clock_gettime(CLOCK_MONOTONIC), and clock_gettime(CLOCK_REALTIME) > all take about 40ns. Of course gettimeofday() only has 1us resolution, > but the other two have perhaps 10ns resolution (I get no duplicate > readings in a tight loop). Other documented clockids include > CLOCK_REALTIME_COARSE: about 10ns to read, but only 1ms resolution > CLOCK_MONOTONIC_COARSE: about 12ns to read, but only 1ms resolution > CLOCK_MONOTONIC_RAW: full resolution but very slow, ~145ns to read > So CLOCK_MONOTONIC seems to be the thing to use here. It won't buy > us anything speed-wise but the extra resolution will be nice. > However, we need to do more research to see if this holds true on > other popular distros.
Isn't this very specific to kernel and glibc versions, depending on things like CONFIG_HZ settings and what level of vDSO support has been backported? -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
