JDK-6200091 : RMI gcInterval is too short by default
  • Type: Enhancement
  • Component: core-libs
  • Sub-Component: java.rmi
  • Affected Version: 1.3.0,5.0
  • Priority: P3
  • Status: Resolved
  • Resolution: Fixed
  • OS: generic,solaris_9
  • CPU: generic,x86
  • Submitted: 2004-11-24
  • Updated: 2007-05-11
  • Resolved: 2005-07-29
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Duplicate :  
Default distributed GC intervals for RMI (set by -Dsun.rmi.dgc.server.gcInterval=.. and -Dsun.rmi.dgc.client.gcInterval=) are 60000 millis or 1 minute. In many cases customers are not aware of the fact that their environment (e.g. the JBoss container) activates RMI. In these cases, they experience poor application performance. This is particularly true in the case of large heap sizes where full GC times can easily reach 10-20 seconds. With 1 minute intervals this means that the JVM spends up to 30% of the time searching for garbage which is not there.
A default value of 10 minutes would cause no harm to applications but would bring the waste of time down to below 5% and thus increase throughput by something like 25% out-of-the-box.

EVALUATION Default values for sun.rmi.dgc.client.gcInterval sun.rmi.dgc.server.gcInterval are now 3600000 (one hour).

WORK AROUND Use these JVM parameters explicitly: -Dsun.rmi.dgc.server.gcInterval=600000 -Dsun.rmi.dgc.client.gcInterval=600000 In most cases you even use a value of 3600000 (1 hour) to make automatic full GC runs really rare. ###@###.### 2004-11-24 18:41:13 GMT

SUGGESTED FIX Use these defaults for the JVM: -Dsun.rmi.dgc.server.gcInterval=600000 -Dsun.rmi.dgc.client.gcInterval=600000 ###@###.### 2004-11-24 18:41:13 GMT

EVALUATION Many performance problems in the field would be avoided or largely reduced ###@###.### 2004-11-24 18:41:12 GMT The default value for the GC interval should be increased for Mustang. ###@###.### 2004-12-01 16:30:01 GMT [These system properties control local GC intervals for the purpose of assisting distributed GC (i.e. GC of exported remote objects).] Regarding "harm to applications", for the record, increasing the default value of the sun.rmi.dgc.client.gcInterval system property could adversely impact the timeliness of local unreachability (and thus local garbage collection) of a remote object-- in the worst case, causing an OutOfMemoryError in the remote object's VM-- as well as the timeliness of java.rmi.server.Unreferenced notifications. This adverse impact would not necessarily occur, or even be likely to occur; it depends highly on the nature of the application, including what client-side GC would otherwise occur. (The "harm" of increasing the default value of the sun.rmi.dgc.server.gcInterval is less compelling.) That said, the described harm of the current low default values, given the current implementation (executing stop-the-world full GCs), is well appreciated-- see 4403367-- and seems like sufficient justification for increasing the default values. More extensive external documentation regarding the precise effects of these system property settings would also be helpful. [Note that RFE 5025281 provides a way to amelioriate the problem by providing a VM option to make full GCs execute concurrently rather than as stop-the-world. Also, the most hoped-for solution would be RFE 4665536, which would allow more sophisticated interaction with the local GC than just being able to request a maximum interval between full GCs.] ###@###.### 2004-12-02 01:50:25 GMT