slapd crashes with ch_realloc of X bytes failed

[Meike Stone <meike.stone@googlemail.com>]

Hello,

since a short time, my slapd crashes often.
I have two servers running in MM replication.
I use openldap version 2.4.30 (for updates are only dedicated timeslots...)
The loglevel is set to 256

I see some strange messages in my log before the slapd crashes:

"ch_realloc of 986032 bytes failed"
---
"ch_malloc of 294896 bytes failed"
---
"bdb(ou=root): txn_checkpoint: failed to flush the buffer cache:
Cannot allocate memory"
---
"ch_malloc of 34159 bytes failed"


What does they mean, how can I solve this problem

The System has 16GByte RAM, no other service is running there.
The Database size is about 1500000 entires and the size of the ldif is
about 2Gbyte

Because of the memory messages, I reduced the
cachesize		1000000
dncachesize		1000000
idlcachesize	        3000000

to
cachesize		750000
dncachesize		750000
idlcachesize	        2250000

but the problem exist still again.

I can't believe, that the memory is insufficient. Sysstat is running,
and I see enough cache memory (about 5GByte all time), and the Swap
(2GByte) is almost not used (about 2MByte).

vm.swappiness is set to default (60), so the Swap should used more
before the memory is running out.
OOM Kill is enabled via SYSRQ (signalling of processes), so slapd
should terminated by the kernel ...


My configuration:
== DB_CONFIG ==================================
set_cachesize 2 0 1
set_lg_regionmax 262144
set_lg_bsize 2097152
set_flags DB_LOG_AUTOREMOVE

== slapd.conf ==================================
include			/etc/openldap/schema/core.schema
include			/etc/openldap/schema/cosine.schema
include			/etc/openldap/schema/inetorgperson.schema
include			/etc/openldap/schema/yast.schema
include			/etc/openldap/schema/rfc2307bis.schema

pidfile			/var/run/slapd/slapd.pid
argsfile		        /var/run/slapd/slapd.args

modulepath		/usr/lib/ldap
moduleload		back_bdb
moduleload		syncprov
moduleload		back_monitor
sizelimit		-1
timelimit		300
disallow		bind_anon
require			authc
gentlehup		on
tool-threads	8
serverID		<001|002>

database		bdb
suffix			"ou=demo"
rootdn			"cn=admin"

directory		/var/lib/ldap
loglevel		256

cachesize		750000
dncachesize		750000
idlcachesize	        2250000
cachefree		500

dirtyread
dbnosync
shm_key		7
checkpoint		4096 15

index	objectClass,entryUUID,entryCSN		eq
index	cn					eq,sub
index    ... own indexes

syncrepl rid=<001|002>
    provider=ldap://master-<01|02>
    type=refreshAndPersist
    keepalive=360:10:5
    retry="5 5 300 +"
    searchbase="ou=demo"
    attrs="*,+"
	
overlay			syncprov
mirrormode		TRUE
syncprov-checkpoint	100 5

database 		monitor

==========================================

(I know, dirtyread and dbnosync are not recommended..)


Additional I see messages like:
"bdb_idl_delete_key: c_del id failed: DB_LOCK_DEADLOCK: Locker killed
to resolve a deadlock (-30995)"
Should I care about it?



Thanks Meike