tag:blogger.com,1999:blog-6098392112071095875.post302727065541046896..comments2012-01-10T09:59:45.362-05:00Domingos Netonoreply@blogger.comBlogger18125tag:blogger.com,1999:blog-6098392112071095875.post-5060544579394757252011-04-27T11:10:16.092-04:002011-04-27T11:10:16.092-04:00Check out the following blog for simple explanation of JVM memory structure. It will not take more than 15 min. to assimilate the whole content.<br />Follow :<br /><br /><a href="http://java-espresso.blogspot.com/2011/04/memory-structure-in-jvm.html" rel="nofollow">JVM memory allocation</a>Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-74861403735195227142010-05-11T22:04:12.925-04:002010-05-11T22:04:12.925-04:00thanks a ton for the info !!! :)Rakeshnoreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-40057587254731343082010-04-21T13:24:15.362-04:002010-04-21T13:24:15.362-04:00I am confused. Who is the original author of this article. Look at the link below:<br /><br />http://razanpokhrel.blogspot.com/2010/04/java-developer-on-their-programming.html#linksAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-72296610676198068812010-03-24T06:27:21.835-04:002010-03-24T06:27:21.835-04:00hi,<br />I was searching these info for very long time. Thanks for sharing.<br /><br />thanks again once.laxmihttp://www.blogger.com/profile/11214163825473314880noreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-15028839450098194962010-02-15T21:15:53.163-05:002010-02-15T21:15:53.163-05:00Great post Domingos. I was wondering, what&#39;s your source for this information? Is there any particular Sun JVM architecture reference or something?<br /><br />Cheers,<br />/fuadFuadhttp://www.blogger.com/profile/12250765342904700100noreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-67600786226882032572010-01-18T09:07:08.484-05:002010-01-18T09:07:08.484-05:00Hi anonymous, this is because a field should be aligned to a granularity that is equivalent to its size. This means that field c has to be aligned to a 4 bytes boundary, hence the 3 bytes padding preceding it. Field e, because it has 8 bytes, has to be aligned to an 8 bytes boundary and therefore has a 7 bytes padding before it.Domingos Netohttp://www.blogger.com/profile/16748499695622931125noreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-54929104618870619882010-01-15T01:22:20.152-05:002010-01-15T01:22:20.152-05:00Hi,<br /><br />I have one question after reading this article. In following example :<br />[HEADER: 8 bytes] 8<br />[a: 1 byte ] 9<br />[padding: 3 bytes] 12<br />[c: 4 bytes] 16<br />[d: 1 byte ] 17<br />[padding: 7 bytes] 24<br />[e: 8 bytes] 32<br />[f: 4 bytes] 36<br />[padding: 4 bytes] 40<br /><br />Why padding after &quot;a&quot; is 3 bytes, not 7 bytes? Why padding after &quot;d&quot; is 7 bytes, not 3 bytes?<br /><br />ThanksAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-18330161735692374532009-10-03T20:40:22.108-04:002009-10-03T20:40:22.108-04:00Hello Domingos<br />Excellent article. I was searching these info for very long time. Thanks for sharing.<br />Another question:<br />What changes signifies that a particular thread has acquired the lock on an object and how does that relate to 3 bits of header word.<br /><br />Does the acquiring thread changes the bit order of those 3 bits ? Please let me know, I would like to understand.<br /><br />Thanks<br />//KannanAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-38815896873950845142008-12-16T21:21:00.000-05:002008-12-16T21:21:00.000-05:00Anonymous: I found most of this information by studying the OpenJDK source code and reading the documentation provided at http://openjdk.java.net/Domingos Netohttp://www.blogger.com/profile/16748499695622931125noreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-10177694142817447172008-12-16T21:20:00.000-05:002008-12-16T21:20:00.000-05:00JAlexoid: thanks for the head up, I fixed the typo :)Domingos Netohttp://www.blogger.com/profile/16748499695622931125noreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-80657042380665321212008-12-15T17:15:00.000-05:002008-12-15T17:15:00.000-05:00You have a problem with the mem layout in long array, it's not 1 byte per element it's 8 bytes per element.JAlexoidhttp://www.blogger.com/profile/11226547359996333148noreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-37343976320321031332008-12-15T14:19:00.000-05:002008-12-15T14:19:00.000-05:00can you suggest books or links to documentation, where you found this information. would like to read more about this, but most java books only talk about the language itself, and not specifics like this.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-37739598822869592782008-12-15T04:01:00.000-05:002008-12-15T04:01:00.000-05:00Thanks for the post. Very informative.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-87689816730517838402008-12-15T00:21:00.000-05:002008-12-15T00:21:00.000-05:00Great Post.Eric Yunghttp://www.blogger.com/profile/01541020465305618807noreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-65684229872859722762008-12-14T23:25:00.000-05:002008-12-14T23:25:00.000-05:00I meant "it shares that *word*" above :)Domingos Netohttp://www.blogger.com/profile/16748499695622931125noreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-23746584536443412012008-12-14T22:05:00.000-05:002008-12-14T22:05:00.000-05:00yukuku: the lock information is stored in 3 bits of the first work of the header. It shares that work with the the identity hash code and the age of the object which is for memory management purposes.<BR/><BR/>Hope it helps!Domingos Netohttp://www.blogger.com/profile/16748499695622931125noreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-38110714837975236042008-12-14T21:36:00.000-05:002008-12-14T21:36:00.000-05:00Interesting! <BR/>Reveals the mystery.<BR/>How about object locking? Where is the lock stored?yukukuhttp://www.blogger.com/profile/15226462280828485140noreply@blogger.comtag:blogger.com,1999:blog-6098392112071095875.post-39346543133977717312008-12-14T20:51:00.000-05:002008-12-14T20:51:00.000-05:00cool. thank you very much.Anonymousnoreply@blogger.com