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.lar...@oracle.com <mailto:staffan.lar...@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
