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authorRainer Gerhards <rgerhards@adiscon.com>2008-03-22 10:54:22 +0000
committerRainer Gerhards <rgerhards@adiscon.com>2008-03-22 10:54:22 +0000
commitc75bd2401298498efffd830dea0441dbb3d353fb (patch)
tree8b9c5c735b28fcbf3301c4c5a737b7ea2908c3ed /doc
parentcdcc0e6710a7e11bf1c528bf1728f886dba5a0af (diff)
downloadrsyslog-c75bd2401298498efffd830dea0441dbb3d353fb.tar.gz
rsyslog-c75bd2401298498efffd830dea0441dbb3d353fb.tar.xz
rsyslog-c75bd2401298498efffd830dea0441dbb3d353fb.zip
- Greatly enhanced rsyslogd's filw write performance by disabling file
syncing capability of output modules by default. This feature is usually not required, not useful and an extreme performance hit (both to rsyslogd as well as the system at large). Unfortunately, most users enable it by default, because it was most intuitive to enable it in plain old sysklogd syslog.conf format. There is now a new config setting which must be enabled in order to support syncing. By default it is off. So even if the old-format config lines request syncing, it is not done unless explicitely enabled. I am sure this is a very useful change and not a risk at all. I need to think if I undo it under compatibility mode, but currently this does not happen (I fear a lot of lazy users will run rsyslogd in compatibility mode, again bringing up this performance problem...). - added $ActionfileEnableSync config directive
Diffstat (limited to 'doc')
-rw-r--r--doc/rsyslog_conf.html2
-rw-r--r--doc/v3compatibility.html19
2 files changed, 19 insertions, 2 deletions
diff --git a/doc/rsyslog_conf.html b/doc/rsyslog_conf.html
index 1dc53944..14dad6f6 100644
--- a/doc/rsyslog_conf.html
+++ b/doc/rsyslog_conf.html
@@ -64,7 +64,7 @@ unstable...). So you have been warned ;)</p>
many parameter settings modify queue parameters. If in doubt, use the
default, it is usually well-chosen and applicable in most cases.</p>
<ul>
-<li><a href="rsconf1_actionexeconlywhenpreviousissuspended.html">$ActionExecOnlyWhenPreviousIsSuspended</a></li>
+<li><a href="rsconf1_actionexeconlywhenpreviousissuspended.html">$ActionExecOnlyWhenPreviousIsSuspended</a></li><li>$ActionfileEnableSync [on/<span style="font-weight: bold;">off</span>] - enables file syncing capability of omfile</li>
<li>$ActionQueueCheckpointInterval &lt;number&gt;</li>
<li>$ActionQueueDequeueSlowdown &lt;number&gt; [number
is timeout in <i> micro</i>seconds (1000000us is 1sec!),
diff --git a/doc/v3compatibility.html b/doc/v3compatibility.html
index b17aca82..c2a51139 100644
--- a/doc/v3compatibility.html
+++ b/doc/v3compatibility.html
@@ -87,7 +87,24 @@ via rsyslog.conf. That set of configuration directives is to be
expanded. So far, we support:</p>
<p>$klogSymbolsTwice [on/off]<br>
$DebugPrintKernelSymbols [on/off] # spits *a lot* of messages at startup</p>
-<h2>Queue Modes for the Main Message Queue</h2>
+<h2>Output File Syncing</h2>Rsyslogd tries to keep as compatible to
+stock syslogd as possible. As such, it retained stock syslogd's default
+of syncing every file write if not specified otherwise (by placing a
+dash in front of the output file name). While this was a useful feature
+in past days where hardware was much less reliable and UPS seldom, this
+no longer is useful in today's worl. Instead, the syncing is a high
+performace hit. With it, rsyslogd writes files around 50 *times* slower
+than without it. It also affects overall system performance due to the
+high IO activity. In rsyslog v3, syncing has been turned off by
+default. This is done via a specific configuration directive
+"$ActionFileEnableSync on/off" which is off by default. So even if
+rsyslogd finds sync selector lines, it ignores them by default. In
+order to enable file syncing, the administrator must specify
+"$ActionFileEnableSync on" at the top of rsyslog.conf. This ensures
+that syncing only happens in those installations where the
+administrator actually wanted that (performance-intense) feature. In
+the fast majority of cases (if not all), this dramatically increases
+rsyslogd performance without any negative effects.<h2>Queue Modes for the Main Message Queue</h2>
<p>Either "FixedArray" or "LinkedList" is recommended. "Direct"
is available, but should not be used except for a very good reason
("Direct" disables queueing and will potentially lead to message loss