Shenandoah Events

[Mario Torre]

On Thu, Jan 24, 2019 at 11:10 AM Aleksey Shipilev <shade at redhat.com> wrote:

> On 1/23/19 5:04 PM, Ken Dobson wrote:
> > Do you know of a good way to test the performance overhead of these
> events when they are enabled?
>
> Apart from measuring the actual benchmarks, I don't know.
>
> > As well, the goal with these events is to create something similar to
> the G1 Heap Layout in JMC
> > (screenshot: https://gyazo.com/224574751d48804814163c280764bde5). It is
> used by selecting a GC event
> > in the table on the right which will play the recorded heap information
> beginning at that GC,
> > displaying the Heap Region state changes in a very similar manner to the
> Shenandoah Visualizer. Do
> > you have any recommendations for changes or additional features you
> think would make it more useful
> > for Shenandoah?
>
> What Shenandoah Visualizer does would be good to have in JFR. Per-region
> history data would be nice
> to have, as long as overhead is low.
>

Ken ported the visualiser to JMC already actually, although I think it
needs a little bit more love.

Come to think about, I think intercepting the individual region transitions
> is too fine-grained for
> this to have small theoretical overhead, because region states can change
> a lot. Do we have any idea
> of the JFR sampling overhead both when enabled and disabled? That should
> indeed be our first question.
>

I agree it would be nice to have some data in that regard. Do you think you
can help Ken working out the details to measure the overhead?

Cheers,
Mario

-- 
Mario Torre
Associate Manager, Software Engineering
Red Hat GmbH <https://www.redhat.com>
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