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

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Date:	Wed, 7 Nov 2012 11:58:10 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Rafael Aquini <aquini@...hat.com>
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,  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.

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