SA frontends

[A. Sundararajan]

Hi,

SA uses stop-the-world to debug "snapshot" of the process. BugSpot was 
supposed to be a SA model where you can pause/resume and keep looking at 
different snapshots (as well as use JDI to look at process state). But, 
it was never implemented that way. Over the years lot of stuff 
accumulated assuming the snapshot model as well.

And yes, JSDB may not be directly useful - but you can use most of 
functionality CLHSDB using script "load" as Kris mentioned.

SOQL: Better option is to retrieve heap dump from core/process using 
jmap (or SA internals) and view it by jhat or VisualVM.

-Sundar

Krystal Mok wrote:
> Hi Staffan,
>
> There's at least another frontend, the SA Plugin for Visual VM. I 
> think it only uses the BugSpotAgent for attaching/detaching, otherwise 
> it doesn't use stuff from BugSpot.
> Other tools, e.g. jstack -m, jstack -F, jmap -F, etc., are not exactly 
> SA frontends, but use the SA to implement their functionality.
>
> I use CLHSDB a lot when I poke around the internals of HotSpot. It's 
> good for its purpose, except that history support is really weird, 
> e.g. pressing up arrow give "^[[A". When I need commands not available 
> in CLHSDB yet, I can write a JavaScript file and use "jsload" in 
> CLHSDB to extend it with new commands. Example here: [1].
>
> I seldom use JSDB directly, because the command style of CLHSDB works 
> better, if the commands cover all the needs during a debugging 
> session. When writing new commands for CLHSDB, sometimes I use the 
> "jseval" command to try things out first, before actually writing them 
> into a script file. That overlaps with what JSDB does, but of course 
> prototyping in JSDB would be much nicer than in CLHSDB.
>
> On the top of my wishlist on CLHSDB, I'd wish for:
> 1. better input support (something like jline would be great)
> 2. AMD64 disassembler support (not frontend issue)
> 3. live stepping/breakpointing support (not frontend issue)
>
> If 2 and 3 is implemented, I might be able to spend more time in 
> CLHSDB, where sometimes I have to use a native debugger like gdb. But 
> these aren't frontend issue anyway. I'd be grateful for any advise on 
> how to debug a product build HotSpot with gdb instead of CLHSDB, where 
> a lot of debugging support functions are not available in HotSpot 
> itself and the symbols are inconvenient to access.
>
> On the GUI side, Poonam did a presentation on the SA Plugin in JavaOne 
> 2011. The "Future Plans" part sounds interesting. I think this plugin 
> is the most visible way to use SA for most end users. It'd be great if 
> it could be open sourced and made more extensible, say, embedding a 
> variant of CLHSDB into this plugin.
>
> Regards,
> Kris Mok
>
> [1]:  https://gist.github.com/1393698 
>
> On Wed, Feb 22, 2012 at 4:26 PM, Staffan Larsen 
> <staffan.larsen at oracle.com <mailto:staffan.larsen at oracle.com>> wrote:
>
>     I'm trying to figure out what the different front ends to SA are
>     and how they differ. So far I have identified the following:
>
>     HSDB - basic UI
>     CLHSDB - command line version of HSDB
>     BugSpot - improvement over HSDB ??
>     JSDB - JavaScript command line
>     SOQL - Simple Object Query Language command line
>
>     Have I missed any?
>
>     What are your experiences with these? Which ones are most used?
>     Should we maintain all of them? Can we consolidate them into one?
>     Specifically: what is the difference between HSDB and BugSpot?
>
>     I'd be happy for all and any feedback,
>     /Staffan
>
>