On Thu, May 21, 2020 at 02:12:55AM +0200, Tomas Vondra wrote:
...
I agree that's pretty nice. I wonder how far would we need to go before
reaching a plateau. I'll try this on the other machine with temporary
tablespace on SATA, but that'll take longer.
OK, I've managed to get some numbers from the other machine, with 75GB
data set and temp tablespace on SATA RAID. I haven't collected I/O data
using iosnoop this time, because we already know how that changes from
the other machine. I've also only done this with 128MB work_mem, because
of how long a single run takes, and with 128 blocks pre-allocation.
The patched+tlist means both pre-allocation and with the tlist tweak
I've posted to this thread a couple minutes ago:
master patched patched+tlist
-----------------------------------------------------
sort 485 472 462
hash 24686 3060 559
So the pre-allocation makes it 10x faster, and the tlist tweak makes it
5x faster. Not bad, I guess.
Note: I've slightly tweaked read-ahead on the RAID device(s) on those
patched runs, but the effect was pretty negligible (compared to other
patched runs with the old read-ahead setting).
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
