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RE: loglevel expected performance impact

How does your syslog config look like ?
Did you prefix the filename with the magic - symbol in order to ask for async I/Os on that file?


*.info;mail.none;authpriv.none;cron.none			-/var/log/messages

mail.*								-/var/log/maillog

local4.*								-/var/log/slapd.log

Instead of 

*.info;mail.none;authpriv.none;cron.none			/var/log/messages

mail.*								/var/log/maillog

local4.*								/var/log/slapd.log


Man syslog.conf
   Regular File
       Typically  messages  are  logged  to real files.  The file has to be specified with full
       pathname, beginning with a slash ??/??.

       You may prefix each entry with the minus ??-?? sign to omit syncing the file after every
       logging.   Note  that  you  might  lose information if the system crashes right behind a
       write attempt.  Nevertheless this might give you back some  performance,  especially  if
       you run programs that use logging in a very verbose manner.
-----Original Message-----
From: openldap-technical-bounces@OpenLDAP.org [mailto:openldap-technical-bounces@OpenLDAP.org] On Behalf Of Berend De Schouwer
Sent: Wednesday, June 13, 2012 12:28 PM
To: openldap-technical@openldap.org
Subject: loglevel expected performance impact

I'm running some 2.4.23 servers, and I've encountered some slowdown on loglevel other than 0.  Even 256 (stats; recommended) impacts about a 4x slowdown on queries.  Logging is to syslog.

Running ldapsearch slows from 0.005-0.010 seconds to about 0.030-0.040 seconds; and that includes loading the binary.  That's from localhost to remove potential DNS lookups.

I stumbled across this when logging was wrong, and the slowdown was 100x.

I'm aware that 2.4.23 isn't the latest version.  I'm also quite happy, for now, to run loglevel 0.

I'm wondering if this is the expected behaviour, given that it's the recommended configuration.  Or should I go dig to find the slowdown?

(I did check the indexes, and db_stats, etc.  All seems fine.)

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