Comments from OpenJdk Source

When going through openJDK source found good comments in the source file, thought it would help me a lot for reference....so blogging it

Source: jdk7-b147 (tag)
File Name: hotspot\src\share\vm\memory\space.hpp [line number from 48 to 65]
//  A space is an abstraction for the "storage units" backing
// up the generation abstraction. It includes specific
// implementations for keeping track of free and used space,
// for iterating over objects and free blocks, etc.

// Here's the Space hierarchy:
//
// - Space-- an asbtract base class describing a heap area
// - CompactibleSpace -- a space supporting compaction
// - CompactibleFreeListSpace -- (used for CMS generation)
// - ContiguousSpace -- a compactible space in which all free space
// is contiguous
// - EdenSpace -- contiguous space used as nursery
// - ConcEdenSpace -- contiguous space with a 'soft end safe' allocation
// - OffsetTableContigSpace -- contiguous space with a block offset array
// that allows "fast" block_start calls
// - TenuredSpace -- (used for TenuredGeneration)
// - ContigPermSpace -- an offset table contiguous space for perm gen

----- END of hotspot\src\share\vm\memory\space.hpp

Hotspot Runtime Overview

OpenJDK's doc contains one very important note/document related to JVM runtime overview, this should have been read by me way back but its never late until you do it :)....so here is the link RuntimeOverview. I enjoyed it reading and came to know very key point/areas about the code in OpenJDK.

I tried with WinDbg but found it much easier with VC10 debuging executable found at this link "How to: Debug an Executable Not Part of a Visual Studio Solution".
I am still going through the OpenJDK by debuging and found few useful classes, like for example we have used few JVM options like PermSize which are defined in the file "hotspot/src/share/vm/runtime/globals.hpp", here you can find all the global JVM options defined and we have used in our day to day java application.

First step towards windows debugging for OpenJDK

Yesterday I have installed WinDbg for the purpose of debugging openJDK (mostly around b118), I haven't started using it, will update how it goes

Make downgrade from 3.81 to 3.80

I was trying to build OpenJdk-b118 (for hotspot patch), for this I had to setup few things (as I never did it at my home system), then I realized that my blog had one state for MAKE just saying "Installed make: make version 'GNU Make 3.80'", which was not so simple as is sounds.
I had to struggle for an hour or more to just downgrade the make from 3.81 to 3.80, my mistake previously that I never made a note of it how to do it (downgrading from 3.81 to 3.80), but please note that this information is not complete as well, as I don't remember exactly from where I got the make 3.80 on to my office computer.
TO downgrade, I had to have copy to files one is "make.exe" with version 3.80 and the other is "cygintl-2.dll" (as I said I don't remember how exactly I got this two files, but hope this will be helping me or some other person struggling with downgrade).

argument parsing in Hotspot

Argument parsing in hotspot is done by the class "hotspot\src\share\vm\runtime\arguments.cpp", for example argument "-Xss" would be parsed in this (will be writing more on this when I go through it thoroughly).

Mercurial tutorial

Just found a good Mercurial tutorial at http://hginit.com/00.html