[RFC] Enhanced Garbage Collection Probe Points

[Lukas Berk]

Hey Mark,

* Mark Wielaard <mark at klomp.org> [2012-08-03 09:56]:
> On Thu, 2012-08-02 at 09:10 -0400, Lukas Berk wrote:
[...]
> 
> They look interesting, but do you have some example usage for this? My
> garbage collector knowledge is very rusty. Just some simple description
> when which point would be hit and what interesting data can be
> collected/analysed at that time would be nice to put this in context.
I ran a $stap eventcount.stp hotspot.gc_* -o eventcount.txt style script
and have attached the output.  I'll also start to document the
script(tapset?) I've been using to interpret the probe points I've been
added here.
> 
> Did you happen to talk to the thermostat team? They might give some
> feedback on what kind of information they need and whether these probe
> points would cover their needs.

Yes I have, and I'm working towards what they'd like (idealy we'd like
to track objects from allocation, space to space, and eventually watch
them be collected), however I'd like to make sure this is the correct
starting point and work my way there, one step at a time :)

Cheers,

Lukas
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Finished event counting at Fri Aug  3 10:09:35 2012 EDT.
Total time elapsed: 1021574 ms, 63 events total, 63 after filtering.
TID                       EVENT                          COUNT (RATE Hz)
---                       -----                          ---------------
java(4998)                hotspot.gc_collect_parallel    1 (0.00)
java(5003)                hotspot.gc_collect_PSScavenge_begin 10 (0.00)
java(5003)                hotspot.gc_collect_PSScavenge_end 10 (0.00)
java(5003)                hotspot.gc_collect_delete      2 (0.00)
java(5003)                hotspot.gc_collect_PSParallelCompact_end 2 (0.00)
java(5003)                hotspot.gc_collect_test        1 (0.00)
java(5003)                hotspot.gc_collect_move        3 (0.00)
java(5003)                hotspot.gc_collect_PSParallelCompact_begin 2 (0.00)
java(5077)                hotspot.gc_collect_PSScavenge_begin 5 (0.00)
java(5077)                hotspot.gc_collect_PSScavenge_end 5 (0.00)
java(5139)                hotspot.gc_collect_PSScavenge_end 2 (0.00)
java(5139)                hotspot.gc_collect_PSScavenge_begin 2 (0.00)
java(5330)                hotspot.gc_collect_PSScavenge_begin 4 (0.00)
java(5330)                hotspot.gc_collect_PSScavenge_end 4 (0.00)
java(5776)                hotspot.gc_collect_PSScavenge_end 1 (0.00)
java(5776)                hotspot.gc_collect_PSScavenge_begin 1 (0.00)
java(5827)                hotspot.gc_collect_PSScavenge_end 2 (0.00)
java(5827)                hotspot.gc_collect_PSScavenge_begin 2 (0.00)
java(5864)                hotspot.gc_collect_PSScavenge_end 2 (0.00)
java(5864)                hotspot.gc_collect_PSScavenge_begin 2 (0.00)
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