Questions around codeheaps, codeblobs and code locality

[dean.long at oracle.com]

I wonder if something like -XX:+UseTransparentHugePages would help with 
the iTLB issue.

dl

On 6/3/19 12:14 PM, keita abdoul-kader wrote:
> Hello,
>
> I have been looking into the code cache layout and ways to reduce the high
> amount of iTLB we are observing on some of our workloads. It seems that
> after the works on segmented codeHeaps, the plan was to add support for non
> contiguous codeBlobs as the next step to improve code locality in the code
> cache. is the work  on non contiguous codeBlobs still active ?
>
> Also, does the hotspot has support for any form of code compaction ?
> Compacting the code heap is mentioned in one of the comment in
> relocInfo.hpp, but browsing the source code it seems that once  the
> codeBlobs is filled with the content of a codeBuffer, they are never moved
> in a way to reduce codeheap fragmentation.
>
>   In general, is there an umbrella project or a set of open task around
> improving code locality ?  Please note that most of my observation driving
> this come from spark-sql workloads. Since spark-sql generates dynamically
> generate a lots of code, i might simply be observing a pathological case.
>
> Thanks