Re: inux-next: Tree for Apr 27 (uml + mm/memcontrol.c)

From: David Rientjes
Date: Fri Apr 27 2012 - 19:52:41 EST


On Fri, 27 Apr 2012, Andrew Morton wrote:

> > > Minor matter: that's non-responsive to my suggestion.
> > >
> >
> > If it's moved to a new cgroup then we can just go back to the original
> > point that I made as was trying to avoid: adding #ifdefs all over
> > mm/memcontrol.c in a dozen or so places. A mm/hugetlbcg.c would only be
> > built, natually, when we have "depends on HUGETLB_PAGE" and
> > linux/hugetlb.h takes care of the rest (setting HUGE_MAX_HSTATE for archs
> > that don't define it themselves, in other words only one hugepage size).
>
> And if it isn't moved to a new cgroup then your
> memcg-add-hugetlb-extension-fix.patch is suboptimal. Why is this so
> hard?
>

It _should_ be moved to a new cgroup: there's no reason why someone should
need to enable memcg (and incur ~1% of metadata overhead that comes with
it) if they just want to seperate a global hugepage pool amongst a set of
tasks. Perhaps Aneesh has a reasoning behind this, I dunno.

And yes, memcg-add-hugetlb-extension-fix.patch is a build fix for the
linux-next breakage. If it's seperated out to mm/hugetlbcg.c, this is all
irrelevant. I'd like to determine the direction of this feature before
proposing any fixes for build breakage. In other words, if
memcg-add-hugetlb-extension.patch is rewritten then
memcg-add-hugetlb-extension-fix.patch is useless.
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