User: simone
Date: 00/10/28 05:44:35
Modified: . contconf_howto.html
Log:
Added indication on how to disable overager and resizer.
Revision Changes Path
1.4 +2 -2 jbossweb/contconf_howto.html
Index: contconf_howto.html
===================================================================
RCS file: /products/cvs/ejboss/jbossweb/contconf_howto.html,v
retrieving revision 1.3
retrieving revision 1.4
diff -u -r1.3 -r1.4
--- contconf_howto.html 2000/10/27 10:29:15 1.3
+++ contconf_howto.html 2000/10/28 12:44:35 1.4
@@ -171,9 +171,9 @@
The tag <tt><cache-policy-conf></tt> and its subtags are optional, so you can
specify none, few or all of them.<br>
The tag <tt><min-capacity></tt> specifies the minimum capacity of the cache.
The cache can be empty, but will have room for at least 5 beans (in the above case);
this value cannot be less than 2; the resizer (see below) will shrink the cache
capacity down to but not less than this value.<br>
The tag <tt><max-capacity></tt> specifies the maximum capacity of the cache.
The cache can be empty, but will have room for at most 200 beans (in the above case);
this value cannot be less than the minimum capacity; the resizer (see below) will
enlarge the cache capacity up to but not more than this value.<br>
-The tag <tt><overager-period></tt> specifies the period of the
<b>overager</b>, that is a periodic task that runs (in the above case) every 300
seconds. Purpose of this periodic task is to see if in the cache there are very old
beans, and to passivate them. The age at which a bean is considered too old is also
configurable (see below). While the period of this task is 300 seconds, the first run
happens at a random time between 0 and 300 seconds.<br>
+The tag <tt><overager-period></tt> specifies the period of the
<b>overager</b>, that is a periodic task that runs (in the above case) every 300
seconds. Purpose of this periodic task is to see if in the cache there are very old
beans, and to passivate them. The age at which a bean is considered too old is also
configurable (see below). While the period of this task is 300 seconds, the first run
happens at a random time between 0 and 300 seconds. To disable the overager set the
period to 0.<br>
The tag <tt><max-bean-age></tt> specifies the max age a bean can have before
being passivated by the overager (in this case 600 seconds).<br>
-The tag <tt><resizer-period></tt> specifies the period of the <b>resizer</b>,
that is a periodic task that runs (in the above case) every 400 seconds. Purpose of
this periodic task is to shrink / enlarge the cache capacity upon 3 other parameters
(see below). While the period of this task is 400 seconds, the first run happens at a
random time between 0 and 400 seconds.<br>
+The tag <tt><resizer-period></tt> specifies the period of the <b>resizer</b>,
that is a periodic task that runs (in the above case) every 400 seconds. Purpose of
this periodic task is to shrink / enlarge the cache capacity upon 3 other parameters
(see below). While the period of this task is 400 seconds, the first run happens at a
random time between 0 and 400 seconds. To disable the resizer set the period to 0.<br>
The tags <tt><max-cache-miss-period></tt>,
<tt><min-cache-miss-period></tt> and <tt><cache-load-factor></tt> control
the resizer in this way: the number of cache misses is internally recorded. When the
resizer runs, it sees what is the cache miss rate from the last time it ran. If there
is more than (in the above case) one cache miss every 1 second (min-cache-miss-period)
then the resizer tries to enlarge the cache; if there is less than (in this case) one
cache miss every 60 seconds (max-cache-miss-period) then the resizer tries to shrink
the cache.
How much is the cache enlarged / shrinked ? Here is where the load-factor comes in
the picture. When the resizer shrinks, it tries to shrink the cache so that (in this
case) the ratio number of beans / cache capacity is 0.75; when the resizer enlarges,
it tries to enlarge the cache by a factor 1 / 0.75 == 1.333 (in the above case) plus a
correction calculated from the cache miss rate (so that the more cache miss rate you
have, the more the cache is enlarged, starting from at least 1.333; so if you really
have a lot of cache misses, the resizer may decide to enlarge the cache of a factor
2.0 instead of 1.333 - if there is room for that).<br>
<br>
