Howard Chu wrote: > Alec Matusis wrote: >>> Try repeating the test with MDB_NORDAHEAD set on the environment. >> >> Thank you: with MDB_NORDAHEAD it works on both machines as expected. We have >> a couple of questions and observations. >> >> We have: >> machine 1: >> XFS filesystem, 148GB RAM, 3.13 >> # blockdev --getra /dev/fiob >> 256 >> Shared memory grows to 13GB with or without MDB_NORDAHEAD (as expected) >> >> machine 2: >> EXT4 filesystem, 105GB RAM, 4.15 >> # blockdev --getra /dev/vda2 >> 256 >> Shared memory grows to 83GB without MDB_NORDAHEAD (unexpected) and to 13GB >> with MDB_NORDAHEAD (as expected) >> >> Questions and observations: >> 1. Since “blockdev --getra” shows the same 256 for both machines, why >> MDB_NORDAHEAD was necessary only on machine2? > > This is a stupid question. You claimed both machines have similar setups and > yet > they are running wildly different kernel versions and using completely > different > filesystems, and now you wonder why they behave differently?? > > None of this has anything to do with LMDB. Ask a filesystem or kernel > developer.
For anyone just tuning in - we demonstrated from day 1 the huge difference in performance between different filesystems. http://www.lmdb.tech/bench/microbench/july/#sec11 -- -- Howard Chu CTO, Symas Corp. http://www.symas.com Director, Highland Sun http://highlandsun.com/hyc/ Chief Architect, OpenLDAP http://www.openldap.org/project/
