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Re: slapd lightweight dispatcher

--On Monday, May 15, 2006 5:43 AM -0700 Howard Chu <hyc@symas.com> wrote:

Howard Chu wrote:
What's interesting is that we only see about 19% CPU usage on slapd
(13% user, 6% kernel), even though there are 32 virtual processors
here and 16 worker threads (LWPs) and the database is 100% cached in
RAM. Clearly slapd isn't making as good a use of the available CPUs as
it could; if it were keeping the threads busy we should see right
about 50% CPU usage.

With the lightweight dispatcher and multi-conn array code, we see CPU
utilization go up to 45% (20% user, 25% kernel) and throughput goes up
to about 8800 authentications per second. With the lightweight
dispatcher and the new code with no connections_mutex we get about
8900 authentications per second, and CPU use is at 49% (23% user, 26%

I deployed OL 2.3.23 + LWD + the modifications to connection.c in HEAD on two of my production servers @ Stanford around 18:00 yesterday.

The following link displays the marked improvement of the servers in the pool since that time:


Most notably, ldap8 & ldap9 (the two upgraded systems) are doing 30-40 searches/second while the 2.3.21 systems (ldap4-ldap7) are doing 6.5-9 searches/second. The graph also demonstrates how the two upgraded systems have consistently outperformed the other ldap servers in the pool since being upgraded.


Quanah Gibson-Mount
Principal Software Developer
ITS/Shared Application Services
Stanford University
GnuPG Public Key: http://www.stanford.edu/~quanah/pgp.html