Low-Overhead Heap Profiling

Jeremy Manson jeremymanson at google.com
Mon Aug 17 05:03:39 UTC 2015


Working on it.  I hope to have something to share in the next couple of
weeks.

Jeremy

On Wed, Aug 12, 2015 at 4:28 AM, Kees Jan Koster <kjkoster at gmail.com> wrote:

> Guys,
>
> This piqued my interest. Where can I find the draft JEP and the sources
> for this, please?
>
> Kees Jan
>
>
> > On 4 Aug 2015, at 23:22, Jeremy Manson <jeremymanson at google.com> wrote:
> >
> > Thanks, Staffan.  I've been tinkering with a draft JEP, but it has been
> going slowly because of other craziness in my life.  Some responses:
> >
> > 1) It was a fair bit of work to do it, mostly because it was the first
> time I had tinkered with c2.  This was 5 years ago.  Most of the work since
> then has been dealing with merge conflicts.
> >
> > 2) I did envision a JVMTI interface.  More in the JEP.
> >
> > 3) We have some internal tests, but obviously, we'd have to figure out
> how to externalize them.  For native code, it's much easier only to have to
> worry about building and running on Linux.  Presumably, there's already
> code in there for JVMTI.
> >
> > I'll try to get a JEP going for real, although it might not happen in
> the next week or so, because I'm moving next week (+the JVMLS).
> >
> > Jeremy
> >
> > On Tue, Aug 4, 2015 at 4:04 AM, Staffan Larsen <
> staffan.larsen at oracle.com> wrote:
> > Hi,
> >
> > Sorry for being away for so long.
> >
> > If memory serves me right then the current AllocObjectInNewTLAB JFR
> event was written as a way to quickly get some allocation profiling
> information with a minimum of VM changes. It probably also carried over to
> Hotspot from JRockit. I agree that we can and should collect better
> information than what that event does.
> >
> > I like the approach of instrumenting the interpreter and compiler to do
> the sampling. I had thought it would be a lot of work to do it and was
> reluctant to go down that path. If the work is already done and Jeremy has
> maintained it for a few years without great problems, I think we should
> look at bringing it in. I am not worried about the overhead of a decrement
> and a compare in the allocation path, but of course we should benchmark
> that.
> >
> > It wasn’t clear to me from the discussion how (or if) this was being
> exposed to end users. Was the proposal to just have the native entry points
> in the VM and have these be used by various agents? Would this be part of
> JVMTI?
> >
> > I think a draft JEP would be the logical next step and make it easier
> for us all to discuss what exactly the proposal should contain. Also, let’s
> not forget the need for tests for the feature.
> >
> > Thanks,
> > /Staffan
> >
> >
> >
>
>
> --
> Kees Jan
>
> http://java-monitor.com/
> kjkoster at kjkoster.org
> +31651838192
>
> The secret of success lies in the stability of the goal. -- Benjamin
> Disraeli
>
>
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