On 10/30/16 1:32 PM, Tomas Vondra wrote:
Now, maybe this has nothing to do with PostgreSQL itself, but maybe it's some sort of CPU / OS scheduling artifact. For example, the system has 36 physical cores, 72 virtual ones (thanks to HT). I find it strange that the "good" client counts are always multiples of 72, while the "bad" ones fall in between. 72 = 72 * 1 (good) 108 = 72 * 1.5 (bad) 144 = 72 * 2 (good) 180 = 72 * 2.5 (bad) 216 = 72 * 3 (good) 252 = 72 * 3.5 (bad) 288 = 72 * 4 (good) So maybe this has something to do with how OS schedules the tasks, or maybe some internal heuristics in the CPU, or something like that.
It might be enlightening to run a series of tests that are 72*.1 or *.2 apart (say, 72, 79, 86, ..., 137, 144).
-- Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX Experts in Analytics, Data Architecture and PostgreSQL Data in Trouble? Get it in Treble! http://BlueTreble.com 855-TREBLE2 (855-873-2532) mobile: 512-569-9461 -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
