linux-kernel - Re: [Approach #2] [RFC][PATCH] Remove cgroup member from struct page

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Message-Id: <200809110702.45003.nickpiggin@yahoo.com.au>
Date:	Thu, 11 Sep 2008 07:02:44 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	balbir@...ux.vnet.ibm.com,
	Andrew Morton <akpm@...ux-foundation.org>, hugh@...itas.com,
	menage@...gle.com, xemul@...nvz.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [Approach #2] [RFC][PATCH] Remove cgroup member from struct page

On Wednesday 10 September 2008 21:03, KAMEZAWA Hiroyuki wrote:
> On Thu, 11 Sep 2008 06:44:37 +1000
>
> Nick Piggin <nickpiggin@...oo.com.au> wrote:
> > On Wednesday 10 September 2008 11:49, KAMEZAWA Hiroyuki wrote:
> > > On Tue, 9 Sep 2008 18:20:48 -0700
> > >
> > > Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> > > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2008-09-09
> > > > 21:30:12]: OK, here is approach #2, it works for me and gives me
> > > > really good performance (surpassing even the current memory
> > > > controller). I am seeing almost a 7% increase
> > >
> > > This number is from pre-allcation, maybe.
> > > We really do alloc-at-boot all page_cgroup ? This seems a big change.
> >
> > It seems really nice to me -- we get the best of both worlds, less
> > overhead for those who don't enable the memory controller, and even
> > better performance for those who do.
>
> No trobles for me for allocating-all-at-boot policy.
> My small concern is
>   - wasting page_cgroup for hugepage area.
>   - memory hotplug

In those cases you still waste the struct page area too. I realise that
isn't a good way to justify even more wastage. But I guess it is
relatively low. At least, I would think the users would be more happy to
get a 7% performance increase for small pages! :)


> > Are you expecting many users to want to turn this on and off at runtime?
> > I wouldn't expect so, but I don't know enough about them.
>
> There is no runtime switch. only at boot.

Fine

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