Re: performance very differently for two hosts that are configured identical

[Emmanuel Lecharny <elecharny@apache.org>]

:)...

You are not the only one who faced this kind of problem !

2009/10/15 Zhang Weiwu <zhangweiwu@realss.com>:
> I found the problem. Stupid problem, this took us several days!
>
> Since it has been so many days, I quote the full original question for
> your reference, see the bottom for the last jigsaw of the puzzle
>
> Zhang Weiwu wrote:
>> We have a development server 'emerson' with roughly one third of the
>> performance of our productional server 'bossdog', it runs ldap query 10
>> times faster than the productional server. I checked everything I can to
>> find out the difference, it seems both are equally configured.
>>
>> Test method:
>>
>> emerson:~# time for (( i=0; i<100; i++)); do ldapsearch -xD cn=manager,dc=eoa,dc=cn -w masked -b ou=contacts,ou=realss.com,dc=eoa,dc=cn '(uidNumber=7)' dn; done;
>> [snip]
>> # zhangweiwu, contacts, realss.com, eoa.cn
>> dn: uid=zhangweiwu,ou=contacts,ou=realss.com,dc=eoa,dc=cn
>>
>> # search result
>> search: 2
>> result: 0 Success
>>
>> # numResponses: 2
>> # numEntries: 1
>>
>> real  0m1.047s
>> user  0m0.320s
>> sys   0m0.352s
>>
>> bossdog:~# time for (( i=0; i<100; i++)); do ldapsearch -xD cn=manager,dc=eoa,dc=cn -w masked -b ou=contacts,ou=realss.com,dc=eoa,dc=cn '(uidNumber=7)' dn; done;
>> [snip]
>>
>> real  0m41.790s
>> user  0m0.232s
>> sys   0m0.464s
>>
>>
>> What I have compared:
>>
>>    1. Both server uses Debian Lenney
>>    2. Both server have same DB_CONFIG in /var/lib/ldap
>>    3. Both server have same ACL settings. In fact we tried to reduce the
>>       ACL setting on the slow preforming productional server without
>>       improvement result.
>>    4. Both server uses bdb
>>    5. Compare syslog at log level 256 both server produce same log messages
>>    6. The productional server shows harddisk is twice as fast as
>>       development server (hdparm), free memory more than the development
>>       server, and its dual-core xeon cpu should outperform the VIA CPU
>>       used in the development server, yet slower. The productional
>>       server average load is 0.5 which is not high for dual-CPU (with
>>       hyperthreading display as 4 CPUs to Linux).
>>    7. Productional server DB is then re-built (by rm -rf & slapadd)
>>       without noticeable change in performance.
>>
>> This performance difference resulted the productional server user
>> interface much slower than user's patience.
>>
>> What would you check further in this case? Thanks in advance
>
> The problem is we have been looking into openldap and system
> resource/kernel so much that we forgot other software directly related
> to performance. There had been something wrong made syslog low
> performance, change loglevel to none instantly solves the problem.
>
>



-- 
Regards,
Cordialement,
Emmanuel Lécharny
www.iktek.com