RE: slapd memory and performance problems

["Howard Chu" <hyc@highlandsun.com>]

> -----Original Message-----
> From: owner-openldap-software@OpenLDAP.org
> [mailto:owner-openldap-software@OpenLDAP.org]On Behalf Of Mike Denka

> After experimenting with threads (max number and idletimeout), upgrading
> to v.2.1.16 and applying Howard's new cvs version of tpool.c, I am still
> experiencing some performance issues with slapd.  The most immediate
> problem I see is that the response time for a query under peak loads is
> very slow.  The most obvious oddity is that the slapd threads are
> growing in size over time.

> Upon starting slapd, each thread has a size of about 4800KB.  This
> thread size seems to double after 8 hours or so and grows to about 15M.
> Also, the total memory available on the box seems to degrade over time,
> not just from the increased thread size, but from what appears to be a
> memory leak somewhere since just restarting slapd does not increase the
> available amount of system memory.  Only a reboot recovers system RAM.

If the system memory is not recovered after the slapd process has been
killed, then clearly the problem is not in slapd itself. If this is truly the
situation, then your kernel has a leak, and there's nothing we can do about
this. However, before arriving at this conclusion, bear in mind that memory
consumed by the filesystem buffer cache generally remains in use, but will
flush out as the system needs more for other purposes. So, programs like top
may show very little free memory, but in fact there's some amount still
available on demand.

> I'm running RedHat 8.0 on a platform with an Intel 1G processor and
> 512MB of RAM.  Processor idle time never dips below 90%, no swap space
> is ever used but memory, as I said, diminishes over time.  However,
> performance stays constant and doesn't change as memory degrades (until
> memory drops to below 5M or so, at which time the server must be
> rebooted).

  -- Howard Chu
  Chief Architect, Symas Corp.       Director, Highland Sun
  http://www.symas.com               http://highlandsun.com/hyc
  Symas: Premier OpenSource Development and Support