Request For Comment: Asynchronous Logging

[Liu, Xin]

Hi,

I would like to report my current progress. I have finished all pending
tasks except "hoist async_mode to base class for stdout/err". May I ask
to defer it after this PR? I will create an issue and work on it
immediately after this PR.  It's not difficult but I need to modify the
existing interfaces. I would like to keep this PR almost "added" to ease
reviewers.

If Yasumasa allows me to do so, now the only blocker is CSR. it seems
that Iom and Thomas agree with a global option. Shall we go that way?

Meanwhile, I have pushed all my code to github:
https://github.com/openjdk/jdk/pull/3135

Could you take a look it?

-------------------------------------------------------------
| request                                      | Status     |
-------------------------------------------------------------
| independent NonJavaThread                    | done       |
|-----------------------------------------------------------|
| pass tier1-test with +AsyncLogging           |  [1]       |
|-----------------------------------------------------------|
| inject meta-info to display no. of dropping msg. | done   |
|-----------------------------------------------------------|
| support jcmd VM.log                          |  done      |
|-----------------------------------------------------------|
| preserve accurate decorations                |            |
|-----------------------------------------------------------<- progress
| hoist async_mode to base class for stdout/err|            |
|-----------------------------------------------------------|
| CSR                                          |JDK-8264323 |
|-----------------------------------------------------------<- consensus
|use string table over malloc                  |            |
------------------------------------------------------------|
|use lock-free data structure.                 |            |
-------------------------------------------------------------


[1] the only exception is serviceability/dcmd/gc/RunGCTest.java. it
emits gclog and checks result right away without any synchronization. if
we do run jtreg test with async logging, I need to add an flushing api
in whitebox.


thanks,
--lx