Re: [PATCH v3 4/5][RESEND] page_alloc: Make movablecore_map hashigher priority

[Simon Jeons]

On Tue, 2012-12-11 at 12:56 +0800, Tang Chen wrote:
> If kernelcore or movablecore is specified at the same time
> with movablecore_map, movablecore_map will have higher
> priority to be satisfied.
> This patch will make find_zone_movable_pfns_for_nodes()
> calculate zone_movable_pfn[] with the limit from
> zone_movable_limit[].
> 
> change log:
> Move find_usable_zone_for_movable() to free_area_init_nodes()
> so that sanitize_zone_movable_limit() in patch 3 could use
> initialized movable_zone.
> 
> Reported-by: Wu Jianguo <wujianguo@xxxxxxxxxx>
> 
> Signed-off-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>
> Reviewed-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
> Reviewed-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
> Tested-by: Lin Feng <linfeng@xxxxxxxxxxxxxx>
> ---
>  mm/page_alloc.c |   28 +++++++++++++++++++++++++---
>  1 files changed, 25 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 52c368e..00fa67d 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4839,9 +4839,17 @@ static void __init find_zone_movable_pfns_for_nodes(void)
>  		required_kernelcore = max(required_kernelcore, corepages);
>  	}
>  
> -	/* If kernelcore was not specified, there is no ZONE_MOVABLE */
> -	if (!required_kernelcore)
> +	/*
> +	 * If neither kernelcore/movablecore nor movablecore_map is specified,
> +	 * there is no ZONE_MOVABLE. But if movablecore_map is specified, the
> +	 * start pfn of ZONE_MOVABLE has been stored in zone_movable_limit[].
> +	 */
> +	if (!required_kernelcore) {
> +		if (movablecore_map.nr_map)
> +			memcpy(zone_movable_pfn, zone_movable_limit,
> +				sizeof(zone_movable_pfn));
>  		goto out;
> +	}
>  
>  	/* usable_startpfn is the lowest possible pfn ZONE_MOVABLE can be at */
>  	usable_startpfn = arch_zone_lowest_possible_pfn[movable_zone];
> @@ -4871,10 +4879,24 @@ restart:
>  		for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
>  			unsigned long size_pages;
>  
> +			/*
> +			 * Find more memory for kernelcore in
> +			 * [zone_movable_pfn[nid], zone_movable_limit[nid]).
> +			 */
>  			start_pfn = max(start_pfn, zone_movable_pfn[nid]);
>  			if (start_pfn >= end_pfn)
>  				continue;
>  

Hi Chen,

> +			if (zone_movable_limit[nid]) {
> +				end_pfn = min(end_pfn, zone_movable_limit[nid]);
> +				/* No range left for kernelcore in this node */
> +				if (start_pfn >= end_pfn) {
> +					zone_movable_pfn[nid] =
> +							zone_movable_limit[nid];
> +					break;
> +				}
> +			}
> +

Could you explain this part of codes? hard to understand.

>  			/* Account for what is only usable for kernelcore */
>  			if (start_pfn < usable_startpfn) {
>  				unsigned long kernel_pages;
> @@ -4934,12 +4956,12 @@ restart:
>  	if (usable_nodes && required_kernelcore > usable_nodes)
>  		goto restart;
>  
> +out:
>  	/* Align start of ZONE_MOVABLE on all nids to MAX_ORDER_NR_PAGES */
>  	for (nid = 0; nid < MAX_NUMNODES; nid++)
>  		zone_movable_pfn[nid] =
>  			roundup(zone_movable_pfn[nid], MAX_ORDER_NR_PAGES);
>  
> -out:
>  	/* restore the node_state */
>  	node_states[N_HIGH_MEMORY] = saved_node_state;
>  }


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