RFR: 8229517: Support for optional asynchronous/buffered logging

[Yasumasa Suenaga]

On Thu, 25 Mar 2021 19:00:49 GMT, Xin Liu <xliu at openjdk.org> wrote:

>> src/hotspot/share/runtime/globals.hpp line 2033:
>> 
>>> 2031:           "Milliseconds between asynchronous log flushing")                 \
>>> 2032:                                                                             \
>>> 2033:   product(bool, AsyncLogging, false,                                        \
>> 
>> I think this option is not needed - `async` should be set to `false` by default, and we should control it through `-Xlog` option like other log output options (e.g. `filecount`).
>
> It's possible that a Java process have multiple file-based outputs. A global option `AsyncLogging` can set them all Otherwise, developers have to set async=true individually. It's part of CSR, right?

Yes, it's part of CSR.

I think it is prefer to set `async` to false by default because it should be treated same with `file` / `filecount` / `filesize` on the logger. The user should add `async=true` to the logger what the user want to set to.

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PR: https://git.openjdk.java.net/jdk/pull/3135