Patch: improve huge page support

[Dr Andrew John Hughes]

On 15:49 Wed 04 May     , Andrew Haley wrote:
> My big patch to improve huge page support in now in HotSpot upstream.
> This is a backport.
> 
> The question is: to what branches should we apply this?  It makes the
> use of huge pages much, much easier.  You no longer need root access
> for anything except setting the size of the huge page pool, and the
> huge pages aren't locked in memory, so it's a big improvement for
> usability.  If the new huge page support doesn't work in the kernel,
> it falls back to the old SysV-style huge page allocator.
> 
> Thoughts?
> 

I notice this doesn't actually enable the patch in the Makefile.am.  Have
you built this on any version of IcedTea yet?

I would prefer that this was two separate patches, corresponding to each
upstream changeset.  It makes it easier to just delete the patch file
when it gets backported upstream in OpenJDK6 (and, prior to that, makes
it easier to see what we need to request for backport).

As to branches, things could get tricky, as each of the currently supported
branches has two HotSpot variants as follows:

1.8: hs14 & hs16
1.9: hs17 (default) & hs19
1.10: hs19 (default) & hs20
1.11 (HEAD): hs19 & hs20 (default)

So that's potentially five versions of HotSpot to patch (hs14, hs16, hs17, hs19, hs20)
but it may be that this code has changed little and the same patch can be applied to
several versions.

1.8 is due to become obsolete when we ship 1.11 (according to our 3-release policy [1]),
but that won't be until July and there will be a security update before that on the 7th
of June [2].

So I'll leave the call on 1.8 to you, but I'd expect we at least want this in 1.9,
1.10 and HEAD.

1. http://mail.openjdk.java.net/pipermail/distro-pkg-dev/2011-March/013215.html
2. http://www.oracle.com/technetwork/topics/security/alerts-086861.html

> Andrew.
> 
> 
> 2011-05-04  Andrew Haley  <aph at redhat.com>
> 
> 	* NEWS: Add S7037939, S7034464.
> 	* patches/icedtea-hugepage.patch: Support transparent huge pages
> 	on Linux available since 2.6.38
> 	Disable adaptive resizing if SHM large pages are used.
> 
-- 
Andrew :)

Free Java Software Engineer
Red Hat, Inc. (http://www.redhat.com)

Support Free Java!
Contribute to GNU Classpath and IcedTea
http://www.gnu.org/software/classpath
http://icedtea.classpath.org
PGP Key: F5862A37 (https://keys.indymedia.org/)
Fingerprint = EA30 D855 D50F 90CD F54D  0698 0713 C3ED F586 2A37