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From Stuart Monteith <stuk...@stoo.me.uk>
Subject Re: Tool Prioritisation
Date Tue, 20 Jan 2009 10:06:15 GMT
Hello all,
    I am another member of Steve Poole's team here in IBM.

My priorities list of tools is:

    6) Java Debug Interface (JDI) Connector
    4) Runtime Investigator
    7) Memory Analyser Tool (MAT) Adapter
    1&3) The explorers
   
This is formed from my own personal biases based on the problems I have 
tended to encounter.
My most wanted tool is the JDI connector. As a C programmer it is 
standard practice to attach a
debugger to a running process or to load the core file into the debugger 
and do similar operations.
However, it is only in more recent years that Hotspot has been able to 
allow core files to attach to it.
Kato looks like a good opportunity for other JVMs on lots of other 
platforms to allow Java debuggers to
attach.

_User Stories
_
Here are some user stories:

    * After a long indeterminate time an Error is thrown, JVM continues
      to run but a single customer's transaction is aborted. The JVM has
      been instructed to generate a core file on Error's - such as
      ArrayIndexOutOfBoundsException

    * A server running a long running an application in production
      occasionally deadlocks. The operator causes the JVM to abort,
      restarts the server and then sends the core file to the developer
      to diagnose and fix.

    * While testing a GUI application, some values are incorrect. The
      tester causes the JVM to dump and sends the result to the
      developer to debug.

For many people, attaching a debugger will be sufficient. This makes 
more sense iwhen there is an organisational split between where the 
applications are run and the people who debug them, or where it is 
technically infeasible to have a debugger attached because of 
performance issues and the need to keep the app running.

Nicolas Sterling said:

    /I'm not sure I understand what extra value this provides versus the
    explorer.  A debugger allows you to
    - explore state
    - modify state
    - control execution
    The first is what the explorer does, and the last two don't apply to
    dump artifacts.  I'm sure I'm missing something...
    /

I see what you are saying. I think the difference between a Runtime  
Explorer and this is that being able to use your Java IDE of choice 
would present to the user a view that is consistent with how they 
normally debug their programs. I think that is something that would be 
valuable. To be honest, I think there is still plenty of room for 
improvement in Java debuggers - perhaps some of the views from the 
Explorer could be incorporated into the debuggers themselves.

There are many ifs and buts with this tool, I look forward to hearing 
your thoughts.
 
Regards,
    Stuart


Steve Poole wrote:
> Greetings.
>
> We haven't quite closed on the list of example tools but I think its
> important that we start to prioritise the list we have already.  I'd like to
> spend the rest of the month expanding the requirements we have for our top 3
> or 4  tools.   I would ask you all to respond with your view on the
> prioritisation of the list below.   Highest being most important.
> Additionally , if you have an opinion, please indicate as a comment if the
> tool seem to be relying on  a technical aspect  that is not feasible to
> implement.  (For instance the Native Memory Analysis Tool proposal assumes
> that getting access to memory allocation info from a dump is practicable -
> we have some work to do to figure out what is really achieveable)
>
> If the quick definition for a tool is unclear dont feel shy about asking for
> clarity - or even proposing your own.
>
>
> [ps I've left off Konst's  "debugger with memory" idea as it needs more work
> to explain what the tool would do and look like]
>
>
> The list:
>
> Sample Tools – the primary drivers for developing  JSR User Stories
>
>
> 1: Process Explorer
>
> An Eclipse plugin which allows presentation, navigation and simple querying
> of the elements of a Process Dump.   This tool will demonstrate how to
> explore a dump in an efficient and high performing manner.   Key
> characteristics will include  fast startup time, handling of large
> quantities of data (including summarization), effective navigation to areas
> of interest.
>
>
> 2: Native Memory Analyser Tool
>
> A program that can retrieve native memory allocations by (or on behalf of) a
> Java Runtime and provide trace back to the  Java objects that hold the
> allocation reference.   The tool will be able to display what memory
> allocations exist, the contents of the allocation, and conservatively
> identify which entities hold references to that allocation.  Ideally this
> tool will be able to point to specific fields within Java objects that hold
> the references.   This tool will demonstrate the capabilities   of the API
> to find and display native memory  from a memory manager.    Key
> characteristics will include the performance of the API in  exhaustively
> scanning a dump (for memory allocation handles) and the ability to resolve
> an arbitrary location within the dump into a Java object or similar entity
>
>
> 3: Java Runtime Explorer
>
> Similar to the Process Explorer above this Eclipse plugin will allow the
> presentation, navigation and  simple querying of the elements of a Java
> Runtime dump. This tool will demonstrate how to explore a Java runtime dump
> in an efficient and high performing manner.   Ideally the plugin will also
> demonstrate the APIs ability to  provide some support for  virtualisation of
> Java runtime objects so that implementation specifics concerning objects
> within  the java.lang and java.util packages can be hidden.   Key
> characteristics will include  fast startup time, handling of large
> quantities of data (including summarization), effective navigation to areas
> of interest, useful abstraction of key Java object implementation specifics
>
>
> 4:  Runtime Investigator
>
> A program that can examine a dump and provide guidance on common aliments.
> This tool will provide analysis modules that can report on such items as
> deadlock analysis,  heap occupancy etc The tool will provide extension
> points that will allow others to contribute new analysis modules.  Key
> characteristics of this tool will include handling large quantities of data
> efficiently  (probably via a query language of some type) , ensuring the API
> is generally consumable by programmers and ensuring the API provides the
> data that is actually required to analyze real problems.
>
>
> 5: Java Runtime Trend Analyzer
>
> A tool that can compare multiple dumps and provide trend analysis.  This
> tool will provide analysis modules that can report on such items as  heap
> growth etc The tool will provide extension points that will allow others to
> contribute new analysis modules.  Key characteristics of this tool will
> include exercising  the creation of well formed dumps,  fast startup time,
> correlation between dump objects and handling large quantities of data
> efficiently  (probably via a query language of some type) , ensuring the API
> is generally consumable by programmers and ensuring the API provides the
> data that is actually required to analyze real problems.
>
>
> 6: Java Debug Interface (JDI) Connector
>
> An adapter that allows a Java debugger to interrogate the contents of a Java
> Runtime diagnostic artifact.  This connector will enable similar
> capabilities that exist today with other debuggers than can debug corefiles
> or similar process diagnostic artifacts.   This tool will demonstrate  key
> characteristics such as effective navigation to areas of interest, useful
> abstraction of key Java object implementation specifics and that the API
> provides  the data that required to analyze real problems.
>
>
> 7: Memory Analyser Tool (MAT) Adapter
>
> MAT (http://www.eclipse.org/mat/) is an open source project that consumes
> HPROF and DTFJ supported dumps.  MAT is designed to help find memory leaks
> and reduce memory consumption.  An adapter for MAT will be developed that
> allows MAT to consume HPROF and other dumps via the JSR 326 API.   Key
> characteristics of this adapter will include  handling large quantities of
> data efficiently,  useful abstraction of key Java object implementation
> specifics and  dump type identification.
>
>
> 8 : Retrospector
>
> One of the rationales behind the JSR-326 was complexity of failure &
> performance analysis increasing with CPU core count growth.  This tool will
> showcase this rationale. The tool will present a number of landmarks or
> checkpoints in the code and display  how their mutual temporal ordering and
> latency change (a) over time (b) depending on the number of threads (c)
> depending on the number of available CPU cores etc
>
> Checkpoints can be of different kinds:
>             - well-known events defined by JVMTI (monitor enter/exits,
> method entry/exits, class loads, code generation, thread lifecycle
> events,...)
>            - new kinds of events helping solve particular problems. For
> example, interpreted -> compiled code execution mode change for a method,
> reaching a safepoint (in Hotspot terms), native memory allocation in from
> JNI code, arbitrary checkpoint specified by a user as <method, bytecode
> position> pair (with optional additional refinements or filtering), etc.
>
> This tool will likely require additions within the JRE such that   when a
> checkpoint is reached by a thread, the JRE internally quickly logs this fact
> by adding a record <checkpoint ID, thread ID, timestamp, pc, ...> into a
> buffer, which, at appropriate time, is processed and made available via the
> JSR-326 API. [Note: The logging should be extremely efficient to minimize
> the "observer effect", which seems quite possible with thread-local
> checkpoint event buffer.].
>        The retrospector tool will be able to load the 2 or more checkpoint
> logs and
>        - split up each of them into per-thread events
>        - visualize the checkpoint events mapped onto the timescale
>        - visualize the difference in temporal behavior between two threads
> within the same run of the analyzed app, between two threads within
> different runs on the analyzed app
>
>   

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