Proposal for adding O_DIRECT support into JDK 9

[Volker Simonis]

Hi Lucy,

I've tried your changes on AIX. The good news is that it compiles
fine. The bad news is that the current version doesn't really work on
AIX. That's because AIX only allows to set O_DIRECT when calling
open() but not later on, on a file descriptor with fcntl() (see [1]).
I could fix at least the current regression tests by setting the
O_DIRECT flag right in UnixChannelFactory.open() as demonstrated in
the following addon to your latest change:

http://cr.openjdk.java.net/~simonis/webrevs/2017/8164900_AIX_addon/

Unfortunately I'm not that deep into this topic to foresee if my fix
catches really all paths or if it is really necessary to set O_DIRECT
on a plain file descriptor which we're not opening ourselves. In the
latter case we will either have to switch O_DIRECT support on AIX
completely off or support it only in the case where we open the file
ourselves and disallow it for plain file descriptors.

Besides that, I've also updated the tests to support AIX. The changes
in the Makefile are just for reference because its contents will have
to be moved to jdk/make/test/JtregNative.gmk anyway.

Also please use jdk.test.lib.Platform from the testlibrary for
platform detection instead of parsing the properties yourself. You can
look for example at test/java/lang/System/OsVersionTest.java to see
how it can be used.

Regards,
Volker

[1] https://www.ibm.com/support/knowledgecenter/en/ssw_aix_72/com.ibm.aix.files/fcntl.h.htm

On Wed, Aug 30, 2017 at 6:16 PM, Lu, Yingqi <yingqi.lu at intel.com> wrote:
> Hi Volker,
>
> Thank you very much for the detailed instructions.
>
> Last night, I tried to do "make all" (normally I only do "make jdk") and found the native libraries were built in the build/linux-x86_64-normal-server-release/support/test/jdk/jtreg/native/lib. When using "-nativepath:PATH_TO_LIB" with jtreg, the test passed. I will try "make test-image-jdk-jtreg-native" as well to make sure it works too.
>
> Thank you!
> Lucy
>
>>-----Original Message-----
>>From: Volker Simonis [mailto:volker.simonis at gmail.com]
>>Sent: Wednesday, August 30, 2017 12:48 AM
>>To: Lu, Yingqi <yingqi.lu at intel.com>
>>Cc: Alan Bateman <Alan.Bateman at oracle.com>; Brian Burkhalter
>><brian.burkhalter at oracle.com>; nio-dev at openjdk.java.net; Markle, Seth
>><smarkle at amazon.com>
>>Subject: Re: Proposal for adding O_DIRECT support into JDK 9
>>
>>Hi Lucy,
>>
>>running the tests with native libs is a little tricky and not very well documented
>>but if you know how to do it it is quite simple :)
>>
>>- after doing a build (i.e. make images) you can build the native parts which
>>are required for running the corresponding tests by making the following
>>targets:
>>  make test-image-jdk-jtreg-native (for the jdk/test native parts)
>>  make test-image-hotspot-jtreg-native (for the hotspot/test native parts)
>>- this will create the following subdirectories in your build directory which can
>>be directly used as arguments to -nativepath when running the corresponding
>>JTreg tests:
>>  ./support/test/jdk/jtreg/native/lib (for the jdk/test native parts)
>>  ./support/test/hotspot/jtreg/native/lib (for the hotspot/test native parts)
>>
>>What Alan meant was that he wanted you to build the native part of your
>>tests with the make targets mentioned above (i.e.
>>test-image-jdk-jtreg-native) by putting the build instructions into
>>jdk/make/test/JtregNative.gmk. StringPlatformChars.java was meant as an
>>example of a test which needs a native library which is built in the described
>>way. I hearby second Alan's suggestion :)
>>
>>Regards,
>>Volker
>>
>>On Tue, Aug 29, 2017 at 7:19 PM, Lu, Yingqi <yingqi.lu at intel.com> wrote:
>>> Hi Alan,
>>>
>>> Thank you for your suggestion. I first tried to run StringPlatformChars.java
>>with jtreg and wanted to understand how it works. However the test failed
>>with error message " test result: Error. Use -nativepath to specify the location
>>of native code"
>>>
>>> The command I use to run is:
>>> jtreg
>>> jdk/test/java/lang/String/nativeEncoding/StringPlatformChars.java
>>>
>>> Please let me know if I missed anything.
>>>
>>> Thanks,
>>> Lucy
>>>
>>>>-----Original Message-----
>>>>From: Alan Bateman [mailto:Alan.Bateman at oracle.com]
>>>>Sent: Tuesday, August 29, 2017 3:24 AM
>>>>To: Brian Burkhalter <brian.burkhalter at oracle.com>; Lu, Yingqi
>>>><yingqi.lu at intel.com>
>>>>Cc: Markle, Seth <smarkle at amazon.com>; nio-dev at openjdk.java.net
>>>>Subject: Re: Proposal for adding O_DIRECT support into JDK 9
>>>>
>>>>On 28/08/2017 21:28, Brian Burkhalter wrote:
>>>>> Hi Lucy,
>>>>>
>>>>> I am unsure of the best way to get the native code to build as part
>>>>> of the test build. One example however of where this is done is in
>>>>> <JDK_REPO>/jdk/test/java/awt/JAWT but the test is a shell test and
>>>>> we are trying to move away from those. I do not know exactly what
>>>>> Alan intends by his comment. There are other tests which have
>>>>> pre-compiled shared libraries checked into the SCM. If there is a
>>>>> problem with the native library itself or in locating it, then I
>>>>> would think the test should fail and we would be alerted that there is a
>>problem.
>>>>An example to study is the test in
>>>>jdk/test/java/lang/String/nativeEncoding. The make file to build it is
>>>>jdk/make/test/JtregNative.gmk. No issue with splitting this to a
>>>>separate issue if you decide to include it.
>>>>
>>>>-Alan
>>>