Zero GC Couldn't Recycle In Time

[李木木]

Hi Liden,
              thank you for your quick reply and really sorry for my
mistake.
              I add pictures as attachments this time and we will take your
advice to adjust our gc configuration.

              Following is the caption:
              Pic1:Available Heap Memory Decrease Gradually During The
Second Week
              Pic2:GC Becomes Very Frequent  At Last Which Leads To High
Usage Of CPU
              Pic3:First Part: System.gc Is Called Regularly
                      Second Part:When Stop Calling System.gc Manually,Heap
Memory Increase Gradually Again


Per Liden <per.liden at oracle.com> 于2019年12月4日周三 下午4:58写道：

> Hi,
>
> On 12/4/19 3:42 AM, 李木木 wrote:
> > Hi,
> >        we recently tried zero gc and jdk11 for our online risk-control
>
> ZGC is actually not short for "zero gc" ;)
>
> > service to replace of G1 and jdk8.It works well during the first week,but
> > we find the heap memory increase slowly next week,which seems zgc can't
> > recycle garbage normally because if we call system.gc manually ,the heap
> > memory will fall back to normal.Besides,when we use G1 with the same code
> > ,we never met this sitation.Have you met this condition before and give
> me
> > some advice?
>
> Have you run long enough to see that the heap usage isn't stabilizing at
> some point?
>
> Calling System.gc() doesn't do anything special, it's just doing a
> normal GC like any other. However, you might be calling it more often
> than what ZGC thinks is needed, which could mean that you just happen to
> see less fragmentation building up. If this is the case, you could lower
> the tolerated fragmentation using for example -XX:ZFragmentationLimit=10.
>
> (Btw, it seems the mailing list ate your images)
>
> cheers,
> /Per
>
> >
> >            Following is configuration:
> >            Linux  64  centos   7.4.1708
> >            CPU：40Threads, @2.2GHz
> >            MEM：128G
> >            OS Disk：240G(SSD) * 2
> >            JVM config： -Xmx105g -XX:+UnlockExperimentalVMOptions
> -XX:+UseZGC
> >            Service Type:Web Service
> >            Request QPS:2000
> >           JDK Version：11.0.3
> >
> >            Pic1：Available Heap Memory Decrease Gradually During The
> Second
> > Week
> >
> > [image: 11.png]
> >
> >             Pic2:GC Become Very Frequent  At Last Which Leads To High
> Usage
> > Of CPU
> >
> > [image: 33.png]
> >
> >             Pic3：First Part: System.gc Is Called Regularly
> >                        Second Part:Stop Call System.gc Manually,Heap
> Memory
> > Increase
> >
> > [image: 22.png]
> >
> >               Look forward to your kind reply,Thanks!
> >
>