On Tue, Apr 11, 2017 at 2:59 PM, Claudio Freire <klaussfre...@gmail.com> wrote: > On Tue, Apr 11, 2017 at 3:53 PM, Robert Haas <robertmh...@gmail.com> wrote: >> 1TB / 8kB per page * 60 tuples/page * 20% * 6 bytes/tuple = 9216MB of >> maintenance_work_mem >> >> So we'll allocate 128MB+256MB+512MB+1GB+2GB+4GB which won't be quite >> enough so we'll allocate another 8GB, for a total of 16256MB, but more >> than three-quarters of that last allocation ends up being wasted. >> I've been told on this list before that doubling is the one true way >> of increasing the size of an allocated chunk of memory, but I'm still >> a bit unconvinced. > > There you're wrong. The allocation is capped to 1GB, so wastage has an > upper bound of 1GB.
Ah, OK. Sorry, didn't really look at the code. I stand corrected, but then it seems a bit strange to me that the largest and smallest allocations are only 8x different. I still don't really understand what that buys us. What would we lose if we just made 'em all 128MB? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
