LMDB write performance on Linux

[Howard Chu <hyc@symas.com>]

Quanah noted a few times in IRC that LMDB write performance was a lot slower 
after upgrading from Linux 2.6.x to 3.x. I've also observed some major 
slowdowns on an Ubuntu 3.5.0-23 kernel whenever the dirty page flusher is 
active. Apparently this is a known issue introduced in the 3.0 kernel series

http://lwn.net/Articles/486311/

I'm told that this has been fixed as of Linux 3.10. Unfortunately our most 
recent round of benchmarks has all been run on our 3.5.0-23 system. The SLAMD 
results we obtained for LMDB Modify throughput (tested back in February this 
year) are only about 60% of the speed we expected.

http://lkml.indiana.edu/hypermail/linux/kernel/1309.1/01585.html

--
  -- Howard Chu
  CTO, Symas Corp.           http://www.symas.com
  Director, Highland Sun     http://highlandsun.com/hyc/
  Chief Architect, OpenLDAP  http://www.openldap.org/project/