Questions around codeheaps, codeblobs and code locality

[keita abdoul-kader]

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