Re: BerkeleyDB performance on Linux

[David Boreham <david_list@boreham.org>]

> > With this patch, a slapd that occupies 6.8GB on a system with 8GB of 
> > RAM can run continuously without swapping, delivering a sustained 
> > 11,500 authentications per second. Without the patch, swapping starts 
> > when the process hits the 4.5GB mark (because over 3GB of buffer 
> > cache is in use), and performance drops to only *hundreds* of 
> > authentications per second.
This is interesting. Did you test performance under other workloads ?
Reason I ask is that every time I've tried O_DIRECT in the past performance
suffered (significantly) in the case where I/O is being done (I suspect 
due to reduced
concurrency because the application must block in cases where it
wouldn't have when using OS buffering). Other database productst that
I keep track of (e.g. Postgresql) report similar findings.