Proposal for adding O_DIRECT support into JDK 9

[Brian Burkhalter]

Hi Lucy,

On Oct 4, 2016, at 10:24 AM, Lu, Yingqi <yingqi.lu at intel.com> wrote:

> Anyone else has any feedback/comments?


I looked over the 8164900-2 patch and did not see any conceptual problems per se. I did not however scrutinize all the detailed changes, especially the more extensive ones in FileDispatcherImpl.c. I did however run the patch through our regression tests for IO and NIO and encountered some problems. Firstly the patch breaks the build on OS X [1], Solaris [2], and Windows [3]. Note that the code under src/java.base/unix is built on all Unix systems including Linux, OS X, and Solaris. Secondly but of lesser note there were some warnings during the Linux build [4]. Otherwise the IO and NIO tests succeeded on Linux, but that only suggests that pre-existing functionality is preserved as those tests of course do not exercise the new code for which I suppose tests will be provided in the final version of the patch.

Regards,

Brian

[1] OS X
build/macosx-x64/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:41: error: self-reference in initializer
    static final int O_DIRECT = O_DIRECT;
                                ^
[2] Solaris
build/solaris-x64/support/gensrc/java.base/sun/nio/fs/UnixConstants.java:41: error: self-reference in initializer
    static final int O_DIRECT = O_DIRECT;
                                ^
[3] Windows
jdk\src\java.base\windows\classes\java\io\FileDescriptor.java:76: error: <anonymous java.io.FileDescriptor$1> is not abstract and does not override abstract method getDirect(FileDescriptor) in JavaIOFileDescriptorAccess
            new JavaIOFileDescriptorAccess() {
                                             ^
[4] Linux (Ubuntu 16.04 amd64 desktop)

jdk/src/java.base/unix/native/libnio/ch/FileDispatcherImpl.c: In function ‘readDirect’:
jdk/src/java.base/unix/native/libnio/ch/FileDispatcherImpl.c:104:5: warning: ignoring return value of ‘posix_memalign’, declared with attribute warn_unused_result [-Wunused-result]
     posix_memalign(&bytes, pageSize, newLen);
     ^
jdk/src/java.base/unix/native/libnio/ch/FileDispatcherImpl.c: In function ‘writeDirect’:
jdk/src/java.base/unix/native/libnio/ch/FileDispatcherImpl.c:131:5: warning: ignoring return value of ‘posix_memalign’, declared with attribute warn_unused_result [-Wunused-result]
     posix_memalign(&bytes, pageSize, len);
     ^
jdk/src/java.base/unix/native/libnio/ch/FileDispatcherImpl.c: In function ‘Java_sun_nio_ch_FileDispatcherImpl_readvDirect0’:
jdk/src/java.base/unix/native/libnio/ch/FileDispatcherImpl.c:250:5: warning: ignoring return value of ‘posix_memalign’, declared with attribute warn_unused_result [-Wunused-result]
     posix_memalign(&bytes, pageSize, newLen);
     ^
jdk/src/java.base/unix/native/libnio/ch/FileDispatcherImpl.c: In function ‘Java_sun_nio_ch_FileDispatcherImpl_writevDirect0’:
jdk/src/java.base/unix/native/libnio/ch/FileDispatcherImpl.c:393:5: warning: ignoring return value of ‘posix_memalign’, declared with attribute warn_unused_result [-Wunused-result]
     posix_memalign(&bytes, pageSize, totalLen)