linux-kernel - Re: [PATCH v2 1/4] memblock tests: add simulation of physical memory with multiple NUMA nodes

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Message-ID: <329ab669-620c-ba9e-3c57-9cb90d55b942@redhat.com>
Date:   Tue, 30 Aug 2022 13:17:56 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Rebecca Mckeever <remckee0@...il.com>,
        Mike Rapoport <rppt@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] memblock tests: add simulation of physical memory
 with multiple NUMA nodes

On 19.08.22 11:05, Rebecca Mckeever wrote:
> Add functions setup_numa_memblock_generic() and setup_numa_memblock()
> for setting up a memory layout with multiple NUMA nodes in a previously
> allocated dummy physical memory. These functions can be used in place of
> setup_memblock() in tests that need to simulate a NUMA system.
> 
> setup_numa_memblock_generic():
> - allows for setting up a custom memory layout by specifying the amount
>   of memory in each node, the number of nodes, and a factor that will be
>   used to scale the memory in each node
> 
> setup_numa_memblock():
> - allows for setting up a default memory layout
> 
> Introduce constant MEM_FACTOR, which is used to scale the default memory
> layout based on MEM_SIZE.
> 
> Set CONFIG_NODES_SHIFT to 4 when building with NUMA=1 to allow for up to
> 16 NUMA nodes.
> 
> Signed-off-by: Rebecca Mckeever <remckee0@...il.com>
> ---
>  .../testing/memblock/scripts/Makefile.include |  2 +-
>  tools/testing/memblock/tests/common.c         | 38 +++++++++++++++++++
>  tools/testing/memblock/tests/common.h         |  9 ++++-
>  3 files changed, 47 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/memblock/scripts/Makefile.include b/tools/testing/memblock/scripts/Makefile.include
> index aa6d82d56a23..998281723590 100644
> --- a/tools/testing/memblock/scripts/Makefile.include
> +++ b/tools/testing/memblock/scripts/Makefile.include
> @@ -3,7 +3,7 @@
>  
>  # Simulate CONFIG_NUMA=y
>  ifeq ($(NUMA), 1)
> -	CFLAGS += -D CONFIG_NUMA
> +	CFLAGS += -D CONFIG_NUMA -D CONFIG_NODES_SHIFT=4
>  endif
>  
>  # Use 32 bit physical addresses.
> diff --git a/tools/testing/memblock/tests/common.c b/tools/testing/memblock/tests/common.c
> index eec6901081af..15d8767dc70c 100644
> --- a/tools/testing/memblock/tests/common.c
> +++ b/tools/testing/memblock/tests/common.c
> @@ -34,6 +34,10 @@ static const char * const help_opts[] = {
>  
>  static int verbose;
>  
> +static const phys_addr_t node_sizes[] = {
> +	SZ_4K, SZ_1K, SZ_2K, SZ_2K, SZ_1K, SZ_1K, SZ_4K, SZ_1K
> +};
> +
>  /* sets global variable returned by movable_node_is_enabled() stub */
>  bool movable_node_enabled;
>  
> @@ -72,6 +76,40 @@ void setup_memblock(void)
>  	fill_memblock();
>  }
>  
> +/**
> + * setup_numa_memblock_generic:
> + * Set up a memory layout with multiple NUMA nodes in a previously allocated
> + * dummy physical memory.
> + * @nodes: an array containing the amount of memory in each node
> + * @node_cnt: the size of @nodes
> + * @factor: a factor that will be used to scale the memory in each node
> + *
> + * The nids will be set to 0 through node_cnt - 1.
> + */
> +void setup_numa_memblock_generic(const phys_addr_t nodes[],
> +				 int node_cnt, int factor)
> +{
> +	phys_addr_t base;
> +	int flags;
> +
> +	reset_memblock_regions();
> +	base = (phys_addr_t)memory_block.base;
> +	flags = (movable_node_is_enabled()) ? MEMBLOCK_NONE : MEMBLOCK_HOTPLUG;
> +
> +	for (int i = 0; i < node_cnt; i++) {
> +		phys_addr_t size = factor * nodes[i];

I'm a bit lost why we need the factor if we already provide sizes in the
array.

Can you enlighten me? :)

Why can't we just stick to the sizes in the array?

-- 
Thanks,

David / dhildenb