RFR: 8207851 JEP Draft: Support ByteBuffer mapped over non-volatile memory
fw at deneb.enyo.de
Thu Jul 26 19:05:22 UTC 2018
* Andrew Dinn:
>> + // TODO - remove the following defines
>> + // for testing we need to define the extra MAP_XXX flags used for
>> + // persistent memory. they will eventually get defined by the
>> + // system and included via sys/mman.h
>> Do you really want to change implementation behavior based on which
>> glibc headers (or kernel headers) were used to build the JDK? It's
>> likely more appropriate to define the constants yourself if they are
>> not available. There is some architecture variance for the MAP_*
>> constants, but in case of MAP_SHARED_VALIDATE, even HPPA has the same
> No, I guess I don't really want to change implementation behaviour based
> on which glibc headers (or kernel headers) were used to build the JDK.
> So, I think I need to modify this so the constants are always defined by
> I have followed the Intel libpmem code in defining the values for these
> constants. Can you provide details of the 'architecture variance' you
> refer to above?
Just a quick note on that: Some of the constants in <sys/mman.h> vary
between the Linux architectures for historic reasons. However, for
MAP_SHARED_VALIDATE, the constant is consistent across all
architectures supported by glibc and in the mainline kernel.
You could add something like this to be on the safe side:
#if MAP_SHARED_VALIDATE != 3
#error Unexpected value for MAP_SHARED_VALIDATE
#else /* !MAP_SHARED_VALIDATE */
#define MAP_SHARED_VALIDATE 3
But I doubt that this is required for this constant.
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