More reliable compressed-oops patch for JOL and some simple improvements [Patch Linked]

[serkan özal]

Hi all,
Sorry for my previous bad formatted mail :(
As I seen, there are two problems/disadvantages with Hotspot SA:
* Process attach problem on MacOSX
* "sa-jdi.jar" version must be same with current JVM version. For example, if the program is run on Java 7, "sa-jdi.jar" for Java 7 must be used. "sa-jdi.jar" of Java 6 is not work on Java 7. But to be sure, I will check it again.



However there are three advantages of Hotspot SA:
* We can always be sure that we get right compressed-oops values since they are directly taken by JVM
* For future works, Hotspot SA gives us more opportunities to play on JVM :)
* Less complex code 

What do you think ?
--
Serkan ÖZAL
> Date: Wed, 10 Sep 2014 10:55:53 +0400
> From: aleksey.shipilev at oracle.com
> To: serkanozal86 at hotmail.com; jol-dev at openjdk.java.net
> Subject: Re: More reliable compressed-oops patch for JOL and some simple improvements [Patch Linked]
> 
> On 09/09/2014 10:30 PM, serkan özal wrote:
> > Currenly, I got out these magic offsets from native codes of JDK. In
> > my opinion, to be sure about them,     * Test as much as all
> > published JDK binaries :) (for JDK 7, such as jdk1.7_u17, jdk1.7_u21,
> > etc ...)    * Looking commit logs of these files if ltheir ayout is
> > changed or not. What do you think about how we can be sure for these
> > magic offsets?
> 
> This does add significant maintenance burden.
> 
> I am thinking: this is why we need to involve Serviceability Agent.
> Hard-coding the offsets seems very wrong. Can we instead ask user to
> supply the relevant sa-jdi.jar, and pull the offsets from there?
> 
> -Aleksey.
> 
> 
>