linux-kernel - Re: [PATCH v11 5/7] virtio_balloon: introduce migration primitives to balloon pages

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Date:	Wed, 7 Nov 2012 20:02:56 -0200
From:	Rafael Aquini <aquini@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>,
	Andi Kleen <andi@...stfloor.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Minchan Kim <minchan@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH v11 5/7] virtio_balloon: introduce migration primitives
 to balloon pages

On Wed, Nov 07, 2012 at 11:58:10AM -0800, Andrew Morton wrote:
> On Wed,  7 Nov 2012 01:05:52 -0200
> Rafael Aquini <aquini@...hat.com> wrote:
> 
> > Memory fragmentation introduced by ballooning might reduce significantly
> > the number of 2MB contiguous memory blocks that can be used within a guest,
> > thus imposing performance penalties associated with the reduced number of
> > transparent huge pages that could be used by the guest workload.
> > 
> > Besides making balloon pages movable at allocation time and introducing
> > the necessary primitives to perform balloon page migration/compaction,
> > this patch also introduces the following locking scheme, in order to
> > enhance the syncronization methods for accessing elements of struct
> > virtio_balloon, thus providing protection against concurrent access
> > introduced by parallel memory migration threads.
> > 
> > ...
> >
> > @@ -122,18 +128,25 @@ static void set_page_pfns(u32 pfns[], struct page *page)
> >  
> >  static void fill_balloon(struct virtio_balloon *vb, size_t num)
> >  {
> > +	struct balloon_dev_info *vb_dev_info = vb->vb_dev_info;
> > +
> > +	static DEFINE_RATELIMIT_STATE(fill_balloon_rs,
> > +				      DEFAULT_RATELIMIT_INTERVAL,
> > +				      DEFAULT_RATELIMIT_BURST);
> > +
> >  	/* We can only do one array worth at a time. */
> >  	num = min(num, ARRAY_SIZE(vb->pfns));
> >  
> > +	mutex_lock(&vb->balloon_lock);
> >  	for (vb->num_pfns = 0; vb->num_pfns < num;
> >  	     vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
> > -		struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY |
> > -					__GFP_NOMEMALLOC | __GFP_NOWARN);
> > +		struct page *page = balloon_page_enqueue(vb_dev_info);
> > +
> >  		if (!page) {
> > -			if (printk_ratelimit())
> > +			if (__ratelimit(&fill_balloon_rs))
> >  				dev_printk(KERN_INFO, &vb->vdev->dev,
> >  					   "Out of puff! Can't get %zu pages\n",
> > -					   num);
> > +					   VIRTIO_BALLOON_PAGES_PER_PAGE);
> >  			/* Sleep for at least 1/5 of a second before retry. */
> >  			msleep(200);
> >  			break;
> 
> linux-next's fill_balloon() has already been converted to
> dev_info_ratelimited().  I fixed everything up.  Please check the result.

Looks great, thanks for doing it

> 
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