Uncollected garbage

[Kirill Ilyukhin]

Roman, Aleksey,

I have to accept the "filler object" explanation.
I could not reproduce the issue on a test server. These int arrays keep
accumulating but the memory is reclaimed when heap usage reaches 70-80%.

Now the question is why did it take that long to reclaim the memory? Before
a restart the JVM was running about 2 hours 20 minutes with heap usage more
than 80%, including ~30 minutes with usage ~90%. Please see the GCeasy
report in my previous mail.

Thank you,
Kirill

On Mon, 20 Dec 2021 at 23:29, Kirill Ilyukhin <kilyukhin at gmail.com> wrote:

> Roman, Aleksey,
>
> Here is what I got at the moment.
>
> Looks like these arrays are really eventually reclaimed, but after more
> than an hour of high GC activity and nearly 100% CPU usage. Seems a bit
> late.
> Please see GCeasy report at
> https://gceasy.io/my-gc-report.jsp?p=c2hhcmVkLzIwMjEvMTIvMjAvLS1nYy4yMDIxLTEyLTExXzA5LTAzLTI5LmxvZy5nei0tMTMtOC0yMg==&channel=WEB
>
> int arrays size corresponds to PNG images size. The biggest are:
> 678x840 - 569,520 elements = 2,278,104 bytes
> 452x560 - 253,120 elements = 1,012,480 byte
>
> Please see full GC log at https://kilyukhin.github.io/gc.awt.image.log.gz
>
> I will run with -verbose:gc and get back to you later.
>
> Thank you,
> Kirill
>
> On Mon, 20 Dec 2021 at 20:39, Roman Kennke <rkennke at redhat.com> wrote:
>
>> > The heap usage is nearly 100% , with these int[] objects occupying 87%.
>> The
>> > JVM process consumes ~100% of CPU, most of which is GC trying to free up
>> > some memory. Does this fit into "filler objects" explanation?
>>
>> Hmm, no, not really.
>>
>> AFAIK, those image objects carry their int[] for image data, and they
>> are accessed by native code, too. Native access to arrays pins the
>> arrays and their containing region. It seems plausible that frequent
>> native access to image data prevents those regions from being collected,
>> at least as long as the region contains one live/reachable image data
>> array. Eventually, those *should* be reclaimed.
>>
>> Can you post heap configuration that is printed by -verbose:gc when
>> application starts, and also typical size of the int arrays?
>>
>> Thanks,
>> Roman
>>
>>