RFR(XS) 8191931: NMT test for anonymous/delegating metadata space sizing

[Zhengyu Gu]

I would like to withdraw this RFR.

Although it is unlikely, in theory, it can encounter any size of 
allocation request, therefore, it can have any type of chunks before 
SpecializedChunk limit exhausted.

I will close the bug as Won't Fix.

Thanks,

-Zhengyu

On 03/15/2018 11:13 AM, Thomas Stüfe wrote:
> Hi Zhengyu,
> 
> http://cr.openjdk.java.net/~zgu/8191931/webrev.00/src/hotspot/share/memory/metaspace.cpp.udiff.html
> 
> Not sure, but would this test not break if the class loader allocates a 
> metablock which does not fit into a specialized chunk before reaching 
> _anon_and_delegating_metadata_specialize_chunk_limit - which is a 
> theoretically valid scenario?
> 
> See calc_chunk_size():
> 
>    if ((_space_type == Metaspace::AnonymousMetaspaceType || _space_type 
> == Metaspace::ReflectionMetaspaceType) &&
>        _mdtype == Metaspace::NonClassType &&
>        sum_count_in_chunks_in_use(SpecializedIndex) < 
> _anon_and_delegating_metadata_specialize_chunk_limit &&
>        word_size + Metachunk::overhead() <= SpecializedChunk) {          
>    <<<<
>      return SpecializedChunk;
>    }
> 
> In other words, encountering small/medium chunks before reaching the 
> spec chunk limit could be, at least according to calc_chunk_size(), a 
> valid albeit rare scenario.
> 
> --
> 
> nits:
> 
> "should use up to"  -> "should use at least"
> "midium" -> "medium"
> 
> Should the comment not be:
> 
> -// _anon_and_delegating_metadata_specialize_chunk_limit small chunks 
> before jump to midium chunks,
> +// _anon_and_delegating_metadata_specialize_chunk_limit specialized 
> chunks before jump to medium chunks,
> 
> ?
> 
> Do we always jump right to medium chunks from specialized chunks?
> 
> --
> 
> If your intention is to test "there shall be no small/medium chunks 
> before we have reached the limit of specialized chunks", would it not be 
> easier to test just that:
> 
> if (sum_count_in_chunks_in_use(MediumIndex) > 0) {
>    assert(sum_count_in_chunks_in_use(SpecializedIndex) >= limit)
> }
> 
> instead of calculating and comparing the capacity?
> 
> Best Regards, Thomas
> 
> 
> 
> On Thu, Mar 15, 2018 at 3:52 PM, Zhengyu Gu <zgu at redhat.com 
> <mailto:zgu at redhat.com>> wrote:
> 
>     Hi,
> 
>     Please review a new gtest to ensure correct sizing for anonymous and
>     reflection delegating classloade's metadata space.
> 
>     Bug: https://bugs.openjdk.java.net/browse/JDK-8191931
>     <https://bugs.openjdk.java.net/browse/JDK-8191931>
>     Webrev: http://cr.openjdk.java.net/~zgu/8191931/webrev.00/index.html
>     <http://cr.openjdk.java.net/~zgu/8191931/webrev.00/index.html>
> 
> 
>     Thanks,
> 
>     -Zhengyu
> 
>