Dieter Kluenter wrote:
Hi,
I am at an early stage of deploying OpenLDAP running on Monstavista
Carrier Grade linux, with Linux-2.6 kernel but modified scheduler.
http://www.mvista.com
For this I compiled and installed OpenLDAP-2.3.27 on my TP T43
notebook and on a x86 Carrier Grade hardware, I'm not sure about the
processor manufacturer and type of this hardware.
On both machines identical DB_CONFIG files, slapd.conf and data have
been set up. I created only 10,000 entries as this would the expected
average database size be.
A ldapsearch on localhost with SuSE-9.3 Linux, after some warming
up the results were levelling at
real 0m0.010s
user 0m0.002s
sys 0m0.003s
with Montavista
real 0m0.827s
user 0m0.014s
sys 0m0.015s
Due to a real time scheduler I was expecting the results to be vice
versa.
Can a RT scheduler or other modifications to the operating system have
a negative influence on performance of OpenLDAP?
You can't expect results to be any better than under non-RT os, since a
RT-scheduler will always add overhead to non-RT processes since it will
preempt much more than a normal OS. I have no experience with
Monta-Vista, however my institution (Politecnico di Milano) develops
RTAI, the Real-Time Application Interface for Linux
(http://www.rtai.org/); I'll check what happens when running OpenLDAP
with that.
In the meanwhile, can you tell something more about Monta Vista's
handling of RT? Does it include the PREEMPT_RT patch, which will likely
become part of Linux in a year or so, or does it rather implement some
custom support to handle preemption?
About your test: are your results an average over a realistic number of
trials? Is the database entirely in cache or does it require any access
to disk? Mallocs under a real-time scheduler might also represent a
significant bottleneck; in this case, slapd should really handle memory
internally, to minimize the amount of system calls.
p.
Ing. Pierangelo Masarati
OpenLDAP Core Team
SysNet s.n.c.
Via Dossi, 8 - 27100 Pavia - ITALIA
http://www.sys-net.it
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