Proposal for adding O_DIRECT support into JDK 9

[Lu, Yingqi]

Hi Brian,

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

Very good point! I only tested on UFS. If we decide not to disable the test, what is the best method to check? fstype? I am sorry that I do not have much experiences with Solaris OS.
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?

Thanks,
Lucy

From: Brian Burkhalter [mailto:brian.burkhalter at oracle.com]
Sent: Wednesday, August 30, 2017 11:19 AM
To: Lu, Yingqi <yingqi.lu at intel.com>
Cc: nio-dev at openjdk.java.net
Subject: Re: Proposal for adding O_DIRECT support into JDK 9

Hi Lucy,

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