RFR: 8281195: Mistakenly used logging causes significant overhead in interpreter [v2]

[Alexey Pavlyutkin]

On Mon, 7 Feb 2022 19:01:38 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Alexey Pavlyutkin has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fixing per review
>
> src/hotspot/share/interpreter/oopMapCache.cpp line 282:
> 
>> 280:   LogStream st(Log(interpreter, oopmap)::trace());
>> 281: 
>> 282:   if (log) st.print("Locals (%d): ", max_locals);
> 
> This seems unfortunate to have these if statements, and a counter goal of the logging framework.  Is there another way to do this without the if statements?

The problem is that here we use multiple print()/cr() statements to make up a single log message, thus we cannot simply use regular log_trace(). The only obvious way to avoid multiple if statements is to quote whole body with one if and introduce else branch without logging. But as I understand the intention of LogStream is exactly to combine a log message as a combination of pieces, so I don't see any problem here

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