UNIXProcess improvements

[Martin Buchholz]

I should have explicitly invited Michael and Xueming to review, as well.

On Fri, Apr 16, 2010 at 09:00, Chris Hegarty <chris.hegarty at oracle.com> wrote:
> Martin,
>
> I filed the following to track this:
>  6944584: Improvements to subprocess handling on Unix

Thanks.

> I took a look at the preliminary changes.
>  * I'm not sure we can remove any previous authors names.

We've considered doing that en masse.

I think it's only old copyrights that can never be removed.

>  * I assume the second part, buffering of data after process
>   termination has not been implemented yet, right?

Right.

> Otherwise look good.
>
> Michael:
>  You may want to take a look at these changes also.
>
> -Chris.
>
> Martin Buchholz wrote:
>>
>> Chris and/or Alan,
>> I am planning some improvements to Process.
>> Please file a bug.
>>
>> Synopsis: Improvements to subprocess handling on Unix
>> Description:
>> Looking at UNIXProcess.java.linux, there are a number of possible
>> improvements:
>>
>> The "process reaper" thread should run in a thread pool to save on
>> thread creation in case of repeated process creation.  Its stack size
>> should be small.
>>
>> If the process reaper thread throws a non-IOException (e.g. OOME)
>> the thread creating the subprocess will hang,
>> waiting for a signal from the reaper thread.
>>
>> The JDK knows when the subprocess terminates.
>> At that time, we cannot yet close the streams,
>> because there may still be unread buffered data, but...
>> the file descriptors underlying the subprocess streams
>> can be drained, then closed, and the drained bytes can
>> be added to the internal buffer.  This will solve most cases
>> of (pandemic) poor file stream hygiene leading to
>> file descriptor exhaustion or simply poor performance.
>>
>> Preliminary fix here:
>> http://cr.openjdk.java.net/~martin/webrevs/openjdk7/UNIXProcess/
>