Class unloading in jdk15

[Vicente Rossello]

Hi,

I can wait for a patch, it doesn't matter. We don't really need class
unloading (at least now), I was just testing. Please let me know if I can
try a patch (once available) or do something else.

I'm planning to switch our production to shenandoah once jdk15 is out (or
at least RC), with class unloading enabled or disabled.

Vicente.



On Mon, Apr 13, 2020 at 3:09 PM Zhengyu Gu <zgu at redhat.com> wrote:

> Hi Vicente,
>
> Thanks for reporting the problem.
>
> I think we have a bug in setting up pacing for evacuation, where we can
> not reuse immediately garbage regions until concurrent class unloading
> is completed. I see a few allocation failures during that phase, that
> sent GCs into STW modes.
>
> In the meanwhile, you way want to play with pacing parameters for
> aggressive pacing.
>
> -Zhengyu
>
> On 4/12/20 1:51 PM, Vicente Rossello wrote:
> > Hi,
> >
> > I tried shenandoah with JDK15 (latest build from builds.shipilev.net) in
> > our build, it works better than with G1, without even tuning anything, so
> > that's great.
> >
> > I also tried enabling class unloading (we have it disabled with G1,
> > we don't really get a lot of memory back, but GC times do increase a
> little
> > bit), but it didn't work with shenandoah, GC times become very high.
> >
> > These are GC logs of our full build, with and without class unloading:
> > https://gist.github.com/cocorossello/2c7e774b89f7cb3e3c97ec5758d879ff
> >
> > Our application is a web application, using dependency injection and
> > dynamic proxies. I have tried to make a reproducer but I couldn't, it's
> not
> > an easy task... Maybe the problem comes from dependency injection that
> > creates proxies...
> >
> > I have tried reducing the build and enabling class load/unload logs
> > (-verbose:class), to see if that helps:
> >
> > https://gist.github.com/cocorossello/f77049148e694b91e785696b1808fb4e
> ->
> > Reduced build, class unloading off, verbose class define
> >
> >
> > https://gist.github.com/cocorossello/52c1c88c782adc1a0537fd8aa92a6c82
> ->
> > Reduced build, class unloading on, verbose class define
> >
> > Please let me know if I can do something else, unfortunately I can't
> share
> > the code.
> >
> > Thank you,
> > Vicente.
> >
>
>