RFR(XXS) 8190729: Adjustment to anonymous metadata space chunk allocation algorithm

[Zhengyu Gu]

Hi Thomas,

Thanks for the quick review.

On 11/27/2017 01:36 PM, Thomas Stüfe wrote:
> Hi Zhengyu,
> 
> looks good.
> 
> (I wonder whether if you just could have given the SpaceManager a back 
> pointer to its enclosing Metaspace instead of handing down _space_type 
> and mdType, but then, those are cleanups we can do later.)
> 
> In SpaceManager, could you please make _space_type - and _mdtype too - 
> const?
Fixed.

> 
> Why do you do this only for non-class metaspace?

Cause I have yet seen any anonymous class space above 1K, I would rather 
leave them alone.

> 
> Could please you embellish the comment in calc_chunk_size() a bit?
Done.

> 
> Would it be possible to have a regression test for this one, maybe as 
> part of the NMT tests? So that if we change the allocator logic in the 
> future, we can be sure not to reintroduce that bug. To me, it would be 
> okay to do this in a follow up item, if you are concerned about the 
> jdk10 code freeze.

Probably gtest or JVM internal test (?), I will have to learn how to 
write one.


Updated webrev: http://cr.openjdk.java.net/~zgu/8190729/webrev.01/

Thanks,

-Zhengyu



> Thank you,
> 
> Kind Regards, Thomas
> 
> 
> On Mon, Nov 27, 2017 at 6:09 PM, Zhengyu Gu <zgu at redhat.com 
> <mailto:zgu at redhat.com>> wrote:
> 
>     Hi,
> 
>     To follow up recent discussion of anonymous metadata space memory
>     usage, I would like submit this simple fix for review.
> 
>     By continuing allocating anonymous metadata space from
>     SpecializeChunk pool, up to 4 chunks, it reduces the waste from 60+%
>     to about 30%.
> 
> 
>     Bug: https://bugs.openjdk.java.net/browse/JDK-8190729
>     <https://bugs.openjdk.java.net/browse/JDK-8190729>
>     Webrev: http://cr.openjdk.java.net/~zgu/8190729/webrev.00/
>     <http://cr.openjdk.java.net/~zgu/8190729/webrev.00/>
> 
>     Test:
> 
>        hotspot_tier1_runtime on Linux x64 (fastdebug and release)
> 
> 
>     Thanks,
> 
>     -Zhengyu
> 
>