RFR (M) 8203837: Split nmethod unloading from nmethod cache cleaning

Erik Österlund erik.osterlund at oracle.com
Tue Jun 5 16:45:49 UTC 2018

Hi Coleen,

Looks like a nice cleanup. I don't mind the cheeky logging changes 
squeezed into this change. Reviewed.


On 2018-05-30 14:23, coleen.phillimore at oracle.com wrote:
> Summary: Refactor cleaning inline caches to after GC do_unloading.
> See CR for more information.  This patch refactors 
> CompiledMethod::do_unloading() to unload nmethods in case of !is_alive 
> oop.  If the nmethod is not unloaded, cleans the inline caches, and 
> exception cache, for unloaded classes and unloaded nmethods.  The 
> CodeCache walk in gc_epilogue is moved earlier to combine with cleanup 
> for class unloading.
> It doesn't add CodeCache walks to any of the GCs, and keeps the G1 
> parallel nmethod unloading intact.  This patch also uses common code 
> for CompiledMethod::clean_inline_caches which was duplicated by the G1 
> functions.
> The patch also fixed a case in AOT where clear_inline_caches should be 
> called instead of clean_inline_caches.   I think neither is necessary 
> for the nmethods that are deoptimized because of redefinition, but 
> clear_inline_caches clears up redefined Methods* not for unloaded 
> nmethods.  Once the method is cleaned by the sweeper, 
> clean_inline_caches will be called on it.  clear vs. clean ...
> The patch also converts TraceScavenge to -Xlog:gc+nmethod=trace. I can 
> revert this part and do it separately; I had just converted it while 
> looking at the output.
> open webrev at http://cr.openjdk.java.net/~coleenp/8203837.01/webrev
> bug link https://bugs.openjdk.java.net/browse/JDK-8203837
> Tested with mach5 hs-tier1-5, the gc-test-suite (including 
> specjbb2015, dacapo, gcbasher), runThese with all GCs with and without 
> class unloading.
> This is an enhancement that we can use for making nmethod cleaning 
> concurrent in ZGC.
> Thanks,
> Coleen

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