Patch: improve huge page support

[Dr Andrew John Hughes]

On 13:00 Thu 05 May     , Andrew Haley wrote:
> On 05/04/2011 04:53 PM, Dr Andrew John Hughes wrote:
> > 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?
> 
> Yes, but it's missing from the email, that's all.
> 

So which version?

> > 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).
> 
> The patches aren't separate, and shouldn't be applied separately.  There
> are no circumstances in which it's appropriate to apply just one, IMO.
> 

They are separate changesets so should be separate patches.  It's very hard
to tell what's in the current patch as it doesn't correspond directly to
an OpenJDK7 changeset.  If one was to appear in OpenJDK6 and not the other,
it would be difficult to work out which parts were from which changeset.

> > 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.
> 
> I suspect so, but I had to do a fair bit of work on the backport,
> as this file has some churn.
> 

Well, merging the two changesets makes this harder as it's now difficult to tell which
bits of the patch came from which changeset, and which bits came from neither but are
a result of backporting.

> > 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
> 
> OK, I see.
> 
> Andrew.

-- 
Andrew :)

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

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