RFR: JDK-8303154: Investigate and improve instruction cache flushing during compilation [v2]

[Vladimir Kozlov]

On Mon, 13 Mar 2023 15:35:36 GMT, Damon Fenacci <duke at openjdk.org> wrote:

>> Did you look on how many times we flush ICache during adapters generation?
>> It has most numerous cases when I looked on it:
>> "CodeCache::commit() is also used for adapters. But adapters uses RuntimeBlob which calls CodeBuffer::copy_code_to()."
>> 
>> I thought we would remove flush from CodeCache::commit() and not from copy_code_to().
>
> @vnkozlov @TobiHartmann I pushed the changes if you want to have a look at them again. Thanks a lot!

@dafedafe I look on stack traces you collected. Please look on this:

 732  Stack: 
    ICache::invalidate_range(unsigned char *, int) icache_bsd_aarch64.hpp:41
    AbstractAssembler::flush() assembler.cpp:110
    SharedRuntime::generate_i2c2i_adapters(MacroAssembler *, int, int, const BasicType *, const VMRegPair *, AdapterFingerPrint *) sharedRuntime_aarch64.cpp:794
    AdapterHandlerLibrary::create_adapter(AdapterBlob *&, int, BasicType *, bool) sharedRuntime.cpp:2970 

`generate_i2c2i_adapters` is called for temporary buffer so we don't need to flush it:
https://github.com/openjdk/jdk/blob/master/src/hotspot/share/runtime/sharedRuntime.cpp#L2870

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PR: https://git.openjdk.org/jdk/pull/12877