Στις Wednesday 12 January 2011 18:45:20 ο/η Tom Lane έγραψε: > Achilleas Mantzios <achill@xxxxxxxxxxxxxxxxxxxxx> writes: > > Στις Wednesday 12 January 2011 17:07:53 ο/η Tom Lane έγραψε: > >> Right offhand I'd wonder whether that was more bound by gettimeofday or > >> by printf. Please try it without printf in the loop. > > > Changed that to smth like: micros_total = micros_total + (double) micros; > > instead of the printf to beat any compiler optimization, and still linux runs at light speed: > > FBSD_TEST : user 0.089s, sys 1.4s > > FBSD_DEV : user 0.183s, sys 3.8s > > LINUX_PROD : user 0.168s, sys 0s > > Well, there's your problem all right: the FBSD_DEV system takes 22X > longer to execute gettimeofday() than the LINUX_PROD system. The > particular plan that 9.0 is choosing is especially vulnerable to this > because it involves a whole lot of calls of the Materialize plan node: > You are absolutely right! Changing kern.timecounter.hardware=TSC (from ACPI-fast) *solved* the slow explain analyze effect. Now i get reasonable EXPLAIN ANALYZE times! It also helps to be running > an OS that is able to read the clock in userspace without invoking a > kernel call. It looks like your Linux box is winning on both counts > compared to your BSD boxes. Next step, if i am lucky tonight, i'll set up a new linux box with 9.0.2 and load the same small (coming from FBSD_DEV) database. So my problem was twofold : a) EXPLAIN ANALYZE performance, b) the particular slow query. It seems there is only b) to solve. (see the previous email) A lot of thanx (but stay tuned ;) > > regards, tom lane > -- Achilleas Mantzios -- Sent via pgsql-admin mailing list (pgsql-admin@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-admin
