4837564: (bf) Please make DirectByteBuffer performance enhancements

[Ulf Zibis]

  Hi,

maybe you remember, that I have discussed some changes with Martin Buchholz related to aligning. See 
thead "Swap should be better done native?" from around april.

-Ulf


Am 11.10.2010 16:50, schrieb Alan Bateman:
>
> A long standing gripe for many is that direct buffers are page aligned with the result that the 
> memory usage can be significantly higher than expected. We've never documented the alignment and 
> I'm not aware of anyone that depends on it (if you do then speak up now!).  The patches here 
> change the implementation so these buffers aren't page aligned by default. A new VM option is 
> introduced to force page alignment if  really needed. Mapped buffers will of course continue to be 
> page aligned.
>
> A related issue is that the addition of the management interface for buffer pools subtly changed 
> the semantics of the MaxDirectMemorySize option. That option used to set a limit on the total 
> capacity of all direct buffers, whereas now it limits the total memory size. This is bug 6743526, 
> and the webrev includes the changes to restore the original semantics (which is course is only 
> interesting when these buffers are page aligned).
>
> The webrev with the changes is here. I'm only looking for a reviewer for the changes to the jdk 
> repo as I will be going to hotspot-runtime-dev for the hotspot change.
>  http://cr.openjdk.java.net/~alanb/4837564/
>
> Thanks,
> Alan.
>