RFR: 8281195: Mistakenly used logging causes significant overhead in interpreter [v4]

[Alexey Pavlyutkin]

On Tue, 8 Feb 2022 06:39:33 GMT, Alexey Pavlyutkin <duke at openjdk.java.net> wrote:

>> Fixes
>> 
>> `bool OopMapCacheEntry::verify_mask(CellTypeState* vars, CellTypeState* stack, int max_locals, int stack_top)`
>> 
>> eliminating frequent generation of log messages with no respect of logging configuration
>> 
>> Verification: N/A (the issue does not have an observable effect)
>> 
>> Regression: hotspot_compiler (20.04 on amd64 )
>
> Alexey Pavlyutkin has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Restores mistakenly lost code

I'd suggest to wrap `LogStream` with something like


struct tracer{
  tracer()
    : _enabled(log_is_enabled(LogLevel::Trace, interpreter, oopmap))
    , _stream(Log(interpreter, oopmap)::trace()) {
  }

  void print(const char* fmt, ...) {
    if (_enabled) {
      va_list args;
      va_start(args, format);
      _stream.print(fmt, args);
      va_end(args);
    }
  }

  void cr() {
    if (_enabled) _stream.cr();
  }

private:
  const bool _enabled;
  LogStream _stream;
};


but `LogStream.print()` requires `format` argument to be string literal. Also `outputStream::print()` and `outputStream::cr()` are not virtual, thus we cannot use dummy stream pointer to suppress logging

-------------

PR: https://git.openjdk.java.net/jdk/pull/7367