I think current SA/hotspot developers are the best judges. I used to be
part of serviceability team and worked on SA among other things in the
past. AFAIK, SA suspend/resume was never really implemented or worked
properly. If that is still thought to be useful, we may to see if we can
improve BugSpot. Or else code could be merged b/w HotSpotAgent and
BugSpotAgent.
JSDB is a javascript shell with SA specific stuff exposed as script
functions. With jsload/jseval in CLHSDB, we can do away with another
tool doing doing script shell and improve CLHSDB as needed. SOQL's
functionality is provided by taking heap dump and viewing it offline.
My take is that a single integrated command line tool would be better.
Thanks
-Sundar
Staffan Larsen wrote:
On 22 feb 2012, at 11:22, A. Sundararajan wrote:
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.
So what does BugSpot have that HSDB does not (and the other way around)? Could
one of them be retired?
And yes, JSDB may not be directly useful - but you can use most of functionality CLHSDB
using script "load" as Kris mentioned.
So maybe CLHSDB can be improved and JSDB retired?
SOQL: Better option is to retrieve heap dump from core/process using jmap (or
SA internals) and view it by jhat or VisualVM.
Same thing here?
Thanks for the feedback,
/Staffan
-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 <[email protected] <mailto:[email protected]>> 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
