On Tue, Apr 21, 2015 at 08:52:29PM +1000, Geoff Swan wrote: > > I have an ldap server that appears to slow down significantly even under > moderate load, and wondered if there were any suggestions as to where to > look. > > Using openldap-2.4.40 with mdb backend, on a dual Xeon (6 cores each) > server with 128GB ram. > Linux kernel 3.13, separate ext4 db volume (SAS). Slapd configured with > 48 threads. > > The problem appears that as soon as there are a handful of write > operations, slapd appears to stall. Binding to the ldap port takes many > seconds (instead of instant), and the slapd process appear to occupy > 100% of a single CPU core. What does your config file look like? In particular, what does this setting look like for you: # Threads - four per CPU threads 8

> 4 per CPU/core was a good > rule of thumb with bdb/hdb. So far in playing with back-mdb, it's > seemed closer to 2 per CPU/core for me in benchmarking. Useful to note. Has this detail ended up in any docs yet?

Brian Reichert wrote: > On Tue, Apr 21, 2015 at 08:23:31AM -0700, Quanah Gibson-Mount wrote: >> --On Tuesday, April 21, 2015 11:54 AM -0400 Brian Reichert >> <reichert(a)numachi.com&gt; wrote: >>> What does your config file look like? >>> >>> In particular, what does this setting look like for you: >>> >>> # Threads - four per CPU >>> threads 8 >> >> According to his summary, he's using 48 threads. > > Thanks for pointing that out; I should finish my coffee before > posting. :) > >> 4 per CPU/core was a good >> rule of thumb with bdb/hdb. So far in playing with back-mdb, it's >> seemed >> closer to 2 per CPU/core for me in benchmarking.

> > Useful to note. Has this detail ended up in any docs yet? No, nor should it. Performance depends on system environment and workload - the right value is one that each site must discover for themselves in their own deployment.