Re: zone movable patches comments

[Andy Whitcroft <apw@shadowen.org>]

Mel Gorman wrote:
> On (10/07/07 20:18), Nick Piggin didst pronounce:
>> Nick Piggin wrote:
>>
>>> I'm not completely against kernelcore=, no. However I do think that
>>> should be a general parameter that exists for the core kernel. I guess it
>>> would override any other reservations and things, and it would specify the
>>> absolute minimum kernelcore.
>>>
>>> Then if you add a movable_mem= (or something -- I don't know what the
>>> exact name should be), then that would also specify the minimum movable
>>> memory, although at a lower priority to kernelcore= (and you could have
>>> the appropriate warnings and such if they cannot be satisfied).
>> Ah yes, I now read Andy's mail and this is what he is suggesting, so
>> yes it seems like a good idea I think.
>>
> 
> *beats keyboard with stick* 
> 
> Does something like the following cover it? Tested on a standalone x86
> and it seemed to behave as expected.
> 
> =====
> 
> This patch adds a new parameter for sizing ZONE_MOVABLE called
> movablecore=. kernelcore is used to specify the minimum amount of memory that
> must be available for all allocation types. movablecore= is used to specify
> the minimum amount of memory that is used for migratable allocations. The
> amount of memory used for migratable allocations determines how large the
> huge page pool could be dynamically resized to at runtime for example.
> 
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> ---
>  Documentation/kernel-parameters.txt |   10 +++++
>  mm/page_alloc.c                     |   61 +++++++++++++++++++++++++++++++-----
>  2 files changed, 64 insertions(+), 7 deletions(-)
> 
> diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.22-zonemovable/Documentation/kernel-parameters.txt linux-2.6.22-movablecore/Documentation/kernel-parameters.txt
> --- linux-2.6.22-zonemovable/Documentation/kernel-parameters.txt	2007-07-09 11:50:18.000000000 +0100
> +++ linux-2.6.22-movablecore/Documentation/kernel-parameters.txt	2007-07-10 11:38:04.000000000 +0100
> @@ -850,6 +850,16 @@ and is between 256 and 4096 characters. 
>  			use the HighMem zone if it exists, and the Normal
>  			zone if it does not.
>  
> +	movablecore=nn[KMG]	[KNL,IA-32,IA-64,PPC,X86-64] This parameter
> +			is similar to kernelcore except it specifies the
> +			amount of memory used for migratable allocations.
> +			If both kernelcore and movablecore is specified,
> +			then kernelcore will be at *least* the specified
> +			value but may be more. If movablecore on its own
> +			is specified, the administrator must be careful
> +			that the amount of memory usable for all allocations
> +			is not too small.
> +
>  	keepinitrd	[HW,ARM]
>  
>  	kstack=N	[IA-32,X86-64] Print N words from the kernel stack
> diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.22-zonemovable/mm/page_alloc.c linux-2.6.22-movablecore/mm/page_alloc.c
> --- linux-2.6.22-zonemovable/mm/page_alloc.c	2007-07-09 11:50:18.000000000 +0100
> +++ linux-2.6.22-movablecore/mm/page_alloc.c	2007-07-10 12:31:39.000000000 +0100
> @@ -137,6 +137,7 @@ static unsigned long __meminitdata dma_r
>    unsigned long __initdata node_boundary_end_pfn[MAX_NUMNODES];
>  #endif /* CONFIG_MEMORY_HOTPLUG_RESERVE */
>    unsigned long __initdata required_kernelcore;
> +  unsigned long __initdata required_movablecore;
>    unsigned long __initdata zone_movable_pfn[MAX_NUMNODES];
>  
>    /* movable_zone is the "real" zone pages in ZONE_MOVABLE are taken from */
> @@ -2980,6 +2981,18 @@ unsigned long __init find_max_pfn_with_a
>  	return max_pfn;
>  }
>  
> +unsigned long __init early_calculate_totalpages(void)
> +{
> +	int i;
> +	unsigned long totalpages = 0;
> +
> +	for (i = 0; i < nr_nodemap_entries; i++)
> +		totalpages += early_node_map[i].end_pfn -
> +						early_node_map[i].start_pfn;
> +
> +	return totalpages;
> +}
> +
>  /*
>   * Find the PFN the Movable zone begins in each node. Kernel memory
>   * is spread evenly between nodes as long as the nodes have enough
> @@ -2993,6 +3006,25 @@ void __init find_zone_movable_pfns_for_n
>  	unsigned long kernelcore_node, kernelcore_remaining;
>  	int usable_nodes = num_online_nodes();
>  
> +	/*
> +	 * If movablecore was specified, calculate what size of
> +	 * kernelcore that corresponds so that memory usable for
> +	 * any allocation type is evenly spread. If both kernelcore
> +	 * and movablecore are specified, then the value of kernelcore
> +	 * will be used for required_kernelcore if it's greater than
> +	 * what movablecore would have allowed.
> +	 */
> +	if (required_movablecore) {
> +		unsigned long totalpages = early_calculate_totalpages();
> +		unsigned long corepages;
> +		
> +		required_movablecore =
> +			roundup(required_movablecore, MAX_ORDER_NR_PAGES);

This roundup is subtle.  This ensures that we get at least as much
MOVABLE as we requested, which is correct, but perhaps it should be
mentioned in the commentary.

> +		corepages = totalpages - required_movablecore;
> +
> +		required_kernelcore = max(required_kernelcore, corepages);
> +	}
> +		
>  	/* If kernelcore was not specified, there is no ZONE_MOVABLE */
>  	if (!required_kernelcore)
>  		return;
> @@ -3173,26 +3205,41 @@ void __init free_area_init_nodes(unsigne
>  	}
>  }
>  
> -/*
> - * kernelcore=size sets the amount of memory for use for allocations that
> - * cannot be reclaimed or migrated.
> - */
> -static int __init cmdline_parse_kernelcore(char *p)
> +static int __init cmdline_parse_core(char *p, unsigned long *core)
>  {
>  	unsigned long long coremem;
>  	if (!p)
>  		return -EINVAL;
>  
>  	coremem = memparse(p, &p);
> -	required_kernelcore = coremem >> PAGE_SHIFT;
> +	*core = coremem >> PAGE_SHIFT;
>  
> -	/* Paranoid check that UL is enough for required_kernelcore */
> +	/* Paranoid check that UL is enough for the coremem value */
>  	WARN_ON((coremem >> PAGE_SHIFT) > ULONG_MAX);
>  
>  	return 0;
>  }
>  
> +/*
> + * kernelcore=size sets the amount of memory for use for allocations that
> + * cannot be reclaimed or migrated.
> + */
> +static int __init cmdline_parse_kernelcore(char *p)
> +{
> +	return cmdline_parse_core(p, &required_kernelcore);
> +}
> +
> +/*
> + * movablecore=size sets the amount of memory for use for allocations that
> + * can be reclaimed or migrated.
> + */
> +static int __init cmdline_parse_movablecore(char *p)
> +{
> +	return cmdline_parse_core(p, &required_movablecore);
> +}
> +
>  early_param("kernelcore", cmdline_parse_kernelcore);
> +early_param("movablecore", cmdline_parse_movablecore);
>  
>  #endif /* CONFIG_ARCH_POPULATES_NODE_MAP */
>  

Looks like a sane extension to this configurable to me.

Acked-by: Andy Whitcroft <apw@shadowen.org>

-apw

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