linux-kernel - Re: [PATCH v3 1/4] mm/balloon_compaction: redesign ballooned pages management

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Date:	Tue, 28 Oct 2014 13:23:34 -0700
From:	Matt Mullins <mmullins@...x.us>
To:	Konstantin Khlebnikov <koct9i@...il.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Konstantin Khlebnikov <k.khlebnikov@...sung.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Rafael Aquini <aquini@...hat.com>,
	Stable <stable@...r.kernel.org>,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: [PATCH v3 1/4] mm/balloon_compaction: redesign ballooned pages
 management

On Tue, Oct 28, 2014 at 11:56:15PM +0400, Konstantin Khlebnikov wrote:
> On Tue, Oct 28, 2014 at 9:47 PM, Matt Mullins <mmullins@...x.us> wrote:
> > On Sat, Sep 27, 2014 at 11:15:16PM +0400, Konstantin Khlebnikov wrote:
> >> This patch fixes all of them.
> >
> > It seems to have rendered virtio_balloon completely ineffective without
> > CONFIG_COMPACTION and CONFIG_BALLOON_COMPACTION, even for the case that I'm
> > expanding the memory available to my VM.
> 
> What do you mean by ineffective?

Ballooning does not change the amount of memory available at all.  Bisecting
the change got me back to this patch.

I'm currently using 3.18-rc2 and running in qemu-kvm-1.6.2-9.fc20.x86_64 via
libvirt-daemon-1.1.3.6-1.fc20.x86_64.

I'll attach my .config; enabling COMPACTION and BALLOON_COMPACTION makes
virtio-ballooning work again.

> That it cannot handle fragmentation? I saw that without compaction
> ballooning works even better:
> it allocates pages without GFP_MOVABLE and buddy allocator returns
> much less scattered pages.
> 
> >
> > Was this intended?  Should Kconfig be updated so that VIRTIO_BALLOON depends on
> > BALLOON_COMPACTION now?
> 
> Nope, this is independent feature.

Good to know, thanks.

View attachment "config-3.18-rc2" of type "text/plain" (48964 bytes)