Proposal for adding O_DIRECT support into JDK 9

[Volker Simonis]

On Fri, Sep 8, 2017 at 6:12 PM, Lu, Yingqi <yingqi.lu at intel.com> wrote:
> Hi Volker,
>
> Sorry for the confusion. Brian's patch is patching on top of your patch. I already included your patch in webrev.08. However, it has issue building on MacOS. Brian's patch fixed it. I will incorporate Brian's patch into webrev.09 which will be online sometime today.
>

Sorry, but I can't see my patch in webrev.08. My fix was in
make/gensrc/GensrcMisc.gmk which isn't touched in
http://cr.openjdk.java.net/~kkharbas/8164900/webrev.08/

Brian's fix is OK for platforms which don't define O_DIRECT at all.
But for Linux it will simply define O_DIRECT to 00 which is wrong! We
have to generate UnixConstants.java from UnixConstants.java.template
with the same CPP defines we use for the compilation of the actual
C-sources because  O_DIRECT is only defined on Linux if we are using
"-D_GNU_SOURCE".

Regards,
Volker

> Please let me know if you have any questions.
>
> Thanks,
> Lucy
>
>>-----Original Message-----
>>From: Volker Simonis [mailto:volker.simonis at gmail.com]
>>Sent: Friday, September 08, 2017 2:58 AM
>>To: Brian Burkhalter <brian.burkhalter at oracle.com>
>>Cc: Lu, Yingqi <yingqi.lu at intel.com>; nio-dev at openjdk.java.net
>>Subject: Re: Proposal for adding O_DIRECT support into JDK 9
>>
>>On Thu, Sep 7, 2017 at 8:38 PM, Brian Burkhalter <brian.burkhalter at oracle.com>
>>wrote:
>>> Hi Lucy,
>>>
>>> On Sep 6, 2017, at 11:38 AM, Lu, Yingqi <yingqi.lu at intel.com> wrote:
>>>
>>> The webrev.08 is available at
>>> http://cr.openjdk.java.net/~kkharbas/8164900/webrev.08/
>>>
>>> It supposes to address the following the issues. Please let me know if
>>> there is anything missing.
>>>
>>>
>>> I was off yesterday so I need to catch up here.
>>>
>>> On Sep 7, 2017, at 12:52 AM, huaming.li at oracle.com wrote:
>>>
>>> I applied the patch, face following compilation error, I worked on
>>> Mac, Darwin Kernel Version 16.7.0.
>>>
>>>
>>/workspace/jdk/jdk10/jdk/src/java.base/unix/classes/sun/nio/fs/UnixChannelFac
>>tory.java:247:
>>> error: cannot find symbol
>>>             oflags |= O_DIRECT;
>>>                       ^
>>>   symbol:   variable O_DIRECT
>>>   location: class UnixChannelFactory
>>>
>>> The same failure occurs of course on Solaris. In the build phase it is
>>> resolved by
>>>
>>> ---
>>> a/src/java.base/unix/classes/sun/nio/fs/UnixConstants.java.template
>>> +++ b/src/java.base/unix/classes/sun/nio/fs/UnixConstants.java.templat
>>> +++ e
>>> @@ -72,6 +72,9 @@
>>>
>>>
>>>
>>>  #ifdef O_DIRECT
>>>      static final int PREFIX_O_DIRECT = O_DIRECT;
>>> +#else
>>> +    // not supported (dummy values will not be used at runtime).
>>> +    static final int PREFIX_O_DIRECT = 00;
>>>  #endif
>>>
>>>
>>>
>>>      static final int PREFIX_S_IAMB =
>>>
>>
>>Sorry but this is now getting a little confusing as it seems we have two different
>>mail threads for this topic.
>>
>>To resolve the build issue we not only need the patch proposed by Brian, but also
>>the following build patch which I've already sent you four days before on the
>>other mail thread [1]:
>>
>>The problem on Linux is caused by the fact that the build doesn't use "-
>>D_GNU_SOURCE" when processing UnixConstants.java.template and therefore
>>"O_DIRECT" isn't visible. In contrast, the compilation of "FileDispatcherImpl.c"
>>always uses "-D_GNU_SOURCE", so you can freely access "O_DIRECT".
>>
>>A quick fix is the following:
>>
>>diff -r 0c49baac8805 make/gensrc/GensrcMisc.gmk
>>--- a/make/gensrc/GensrcMisc.gmk        Wed Aug 30 18:54:50 2017 +0200
>>+++ b/make/gensrc/GensrcMisc.gmk        Mon Sep 04 19:37:35 2017 +0200
>>@@ -63,7 +63,7 @@
>> define generate-preproc-src
>>        $(call MakeDir, $(@D))
>>        ( $(NAWK) '/@@END_COPYRIGHT@@/{exit}1' $< && \
>>-         $(CPP) $(CPP_FLAGS) $(SYSROOT_CFLAGS) $< \
>>+         $(CPP) $(CPP_FLAGS) $(SYSROOT_CFLAGS) $(CFLAGS_JDKLIB) $< \
>>              2> >($(GREP) -v '^$(<F)$$' >&2) \
>>              | $(NAWK) '/@@START_HERE@@/,0' \
>>              |  $(SED) -e 's/@@START_HERE@@/\/\/ AUTOMATICALLY GENERATED
>>FILE - DO NOT EDIT/' \
>>
>>which worked for me on Linux/Solaris/AIX (haven't tested on Mac).
>>
>>I think it was always a mistake that we haven't generated the UnixConstants with
>>the same C-Flags that we've also used to compile the files which used them. It
>>was probably just luck that we've not run into problems until now.
>>
>>[1] http://mail.openjdk.java.net/pipermail/nio-dev/2017-September/004478.html
>>
>>> I am currently running a build+regression job on Linux, macOS,
>>> Solaris, and Windows.
>>>
>>> Thanks,
>>>
>>> Brian