linux-kernel - Re: [PATCHv1 5/8] xen/balloon: rationalize memory hotplug stats

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Message-ID: <20150625213113.GP14050@olila.local.net-space.pl>
Date:	Thu, 25 Jun 2015 23:31:13 +0200
From:	Daniel Kiper <daniel.kiper@...cle.com>
To:	David Vrabel <david.vrabel@...rix.com>
Cc:	xen-devel@...ts.xenproject.org,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv1 5/8] xen/balloon: rationalize memory hotplug stats

On Thu, Jun 25, 2015 at 08:54:45PM +0200, Daniel Kiper wrote:
> On Thu, Jun 25, 2015 at 08:38:36PM +0200, Daniel Kiper wrote:
> > On Thu, Jun 25, 2015 at 06:11:00PM +0100, David Vrabel wrote:
> > > The stats used for memory hotplug make no sense and are fiddled with
> > > in odd ways.  Remove them and introduce total_pages to track the total
> > > number of pages (both populated and unpopulated) including those within
> > > hotplugged regions (note that this includes not yet onlined pages).
> > >
> > > This will be useful when deciding whether additional memory needs to be
> > > hotplugged.
> > >
> > > Signed-off-by: David Vrabel <david.vrabel@...rix.com>
> >
> > Nice optimization! I suppose that it is remnant from very early
> > version of memory hotplug. Probably after a few patch series
> > iterations hotplug_pages and balloon_hotplug lost their meaning
> > and I did not catch it. Additionally, as I can see there is not
> > any consumer for total_pages here. So, I think that we can go
> > further and remove this obfuscated code at all.
>
> Err... Ignore that. I missed next patch... Should not both of them
> merged in one or commit comment contain clear info that this will
> be used by next patch.

This patch, #6 and probably #3 change reserve_additional_memory() behavior.
Please check comment before that function and update it accordingly.

It looks that balloon_stats.total_pages is used only in memory hotplug case.
Please do references (and definition) to it inside #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
like it is done in balloon_stats.hotplug_pages and balloon_stats.balloon_hotplug case.

Daniel
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