Proposal for adding O_DIRECT support into JDK 9

[Philippe Marschall]

Hi

I'm just a lurker so excuse me when overstep some boundaries here.
Assuming FileStore#getBlockSize stays:
- Could that be changed into a default method? That would be a help
for any file system implementer (eg myself) and would also simplify
JrtFileStore and ZipFileStore.
- Could the Javadoc be updated to state that throwing
UnsupportedOperationException is valid?

Cheers
Philippe

On Wed, Nov 16, 2016 at 11:14 PM, Lu, Yingqi <yingqi.lu at intel.com> wrote:
> Hi All,
>
>
>
> Our most recent version of our DirectIO patch is available at
> http://cr.openjdk.java.net/~kkharbas/8164900/webrev.04/
>
> In this version, we have modified the following items:
>
> 1.       Remove ByteBuffer.allocateDirectAligned() and
> ByteBuffer.isAligned(). Instead, using existing APIs alignmentOffset() and
> alignedSlice()
>
> 2.       Use Block Size as the alignment value instead of OS page size
>
> 3.       Create a function named getBlockSize from FileStore class
>
> 4.       Implement DirectIO for Windows
>
> 5.       JTreg test passed for Windows, Linux and OS X with regarding to the
> DirectIO changes we made
>
>
>
> Please let us know your comments and feedback. Thank you very much for your
> consideration!
>
>
>
> Thanks,
>
> Lucy
>
>
>
> From: nio-dev [mailto:nio-dev-bounces at openjdk.java.net] On Behalf Of Lu,
> Yingqi
> Sent: Sunday, November 06, 2016 9:37 AM
> To: Alan Bateman <Alan.Bateman at oracle.com>
> Cc: Kharbas, Kishor <kishor.kharbas at intel.com>; David Holmes
> <david.holmes at oracle.com>; core-libs-dev at openjdk.java.net;
> nio-dev at openjdk.java.net; Thomas Stüfe <thomas.stuefe at gmail.com>; Kaczmarek,
> Eric <eric.kaczmarek at intel.com>
> Subject: Re: Proposal for adding O_DIRECT support into JDK 9
>
>
>
> Hi Alan,
>
>
>
> Thank you very much for your suggestion. FileStore is a better home for the
> alignment value. We will use It in our next version of the patch and update
> here for review soon.
>
> Thanks,
>
> Lucy
>
> Sent from my iPhone
>
> On Nov 6, 2016, at 9:04 AM, Alan Bateman <Alan.Bateman at oracle.com> wrote:
>
> On 06/11/2016 15:51, Lu, Yingqi wrote:
>
> Another approach might be use ioctl to get the block size and use that as
> the alignment value. I think ioctl is available on UNIX based OSes (please
> chime in if I miss any OS here) and has a similar call for Windows named
> DeviceIoControl. The request code of ioctl is different from OS to OS, but
> we could address that in the native code.
>
>
>
> A possible approach (I think I mentioned this in one of the early mails) is
> to have FileStore expose the block size that can be use to align and size
> the buffer.
>
> -Alan