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(ITS#7222) Slapd hangs on high load

Full_Name: Hrvoje
Version: 2.4.30
OS: Centos 6.2 x86_64
URL: http://free-zg.t-com.hr/HrvojeHabjanic/hang2.log
Submission from: (NULL) (


While testing openlap, with some of my data, slapd regularly hangs. I did manage
to "catch" it, but i need expert's interpretation of traces.

I' using db-5.3.15 (latest), compiled with:

../dist/configure \
                --enable-shared --enable-static \
                --enable-tcl --with-tcl=/usr/lib64 \
                --enable-cxx --enable-sql \
                --enable-java \
                --enable-test \
                --with-tcl=/usr/lib64/tcl8.5 \
                --disable-rpath \
                --enable-debug \

and openldap-2.4.30, compiled with:

CFLAGS="-g -I/usr/local/db/include" CPPFLAGS="-g -I/usr/local/db/include"
LDFLAGS="-L/usr/local/db/lib -Wl,-R/usr/local/db/lib" ./configure \
 --prefix=/usr/local/openldap \
 --enable-local \
 --enable-rlookups \
 --with-tls=no \
 --with-cyrus-sasl \
 --enable-wrappers \
 --enable-passwd \
 --enable-cleartext \
 --enable-crypt \
 --enable-spasswd \
 --disable-lmpasswd \
 --enable-modules \
 --disable-sql \
 --enable-slapd \
 --enable-bdb \
 --enable-hdb \
 --enable-ldap \
 --enable-meta \
 --enable-monitor \
 --enable-null \
 --enable-shell \
 --disable-ndb \
 --enable-passwd \
 --enable-sock \
 --disable-perl \
 --enable-relay \
 --disable-shared \
 --disable-dynamic \
 --enable-overlays=mod \
 --enable-mdb \

Slapd is configured to use slapd.d directory (db). Inside, two databases are
configured - ie. ou=p,dc=pero,dc=com and ou=d,dc=pero,dc=com, including monitor
db. First database is using 10Gb on disk, and have around 10M unique dn's, while
second one is using around 3-4Gb, few mil. dn's.

Server have 16G of ram, and 2xquad core CPU - total of 8 cpu's (and disks are

I'm using python scripts to generate load on openldap. First i fill in required
data (10Gb), and then do some transaction processing (read/update/write).

Filling part goes without problems, but on transaction processing, slapd
regularly gets stuck. I'm only able to trigger this using more than one
connection - simulating  couple of clients, and high load (1-2 req/sec).
Complete traces from gdb when this happens, are
http://free-zg.t-com.hr/HrvojeHabjanic/hang2.log .

So, am i doing something wrong or openldap is...?