Proposal for adding O_DIRECT support into JDK 9

[Brian Burkhalter]

Hi Lucy,

On Aug 30, 2017, at 10:57 AM, Lu, Yingqi <yingqi.lu at intel.com> wrote:

> Thank you very much for testing it on AIX and patching the current version for AIX. This is really helpful!

Agreed!

> Regarding to setting O_DIRECT to a file descriptor, I remember Alan had some concerns before. I will let either Alan or Brian to double confirm. Alan/Brian, please also provide some guidance on how should we work this feature with AIX.

I was just looking over Volker’s patch and will see whether there are any issues there. At first glance it looks OK but I’d have to go back over the e-mail trail to see which concerns were raised previously.

> I also found that Windows flag setting FILE_FLAG_NO_BUFFERING and FILE_FLAG_WRITE_THROUGH are missing in the most recent version of the patch.

Please do. I was also wondering whether there is an equivalent to mincore() or something which could enable DirectIOTest on Windows.

> I will add it back in the next version together with the new test cases and hopefully changes for AIX.

I ran version .06 through our regression harness. The results are as expected for now: DirectIOTest fails on all platforms on which it is run due to the absence of the native library, and all DIO tests fail on Solaris. All pre-existing NIO tests in the harness succeed on all platforms.

With respect to Solaris, the DIO read/write tests fail because the file system type is not supported for DIO. I wonder whether we need to disable this test on Solaris or add a check of the file system type to determine whether it is either NFS or UFS? [1]

Thanks,

Brian

[1] http://docs.oracle.com/cd/E36784_01/html/E36874/directio-3c.html
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