linux-kernel - Re: [Xen-devel] [PATCH] xen/balloon: Set balloon's initial state to number of existing RAM pages

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Date:	Thu, 07 Nov 2013 08:41:46 +0800
From:	Bob Liu <bob.liu@...cle.com>
To:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
CC:	konrad.wilk@...cle.com, david.vrabel@...rix.com,
	xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH] xen/balloon: Set balloon's initial state
 to number of existing RAM pages


On 11/07/2013 04:37 AM, Boris Ostrovsky wrote:
> Currently balloon's initial value is set to max_pfn which includes
> non-RAM ranges such as MMIO hole. As result, initial memory target
> (specified by guest's configuration file) will appear smaller than
> what balloon driver perceives to be the current number of available
> pages. Thus it will balloon down "extra" pages, decreasing amount of
> available memory for no good reason.
> 

This fix the strange behavior I mentioned yesterday, every time after
guest started balloon driver will be triggered unreasonably.

> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> ---
>  drivers/xen/balloon.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index b232908..1b62304 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -641,7 +641,7 @@ static int __init balloon_init(void)
>  
>  	balloon_stats.current_pages = xen_pv_domain()
>  		? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
> -		: max_pfn;
> +		: get_num_physpages();

By the way, should the other places using max_pfn also be changed with
get_num_physpages()?

>  	balloon_stats.target_pages  = balloon_stats.current_pages;
>  	balloon_stats.balloon_low   = 0;
>  	balloon_stats.balloon_high  = 0;
> 

-- 
Regards,
-Bob
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