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Date:   Tue, 6 Sep 2022 15:17:46 +0200
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To:     Rebecca Mckeever <remckee0@gmail.com>,
        Mike Rapoport <rppt@kernel.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <cover.1662264560.git.remckee0@gmail.com>
 <49b96ce88dece5b394d5dd4332c1572da917b30a.1662264560.git.remckee0@gmail.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
Subject: Re: [PATCH v4 1/4] memblock tests: add simulation of physical memory
 with multiple NUMA nodes
In-Reply-To: <49b96ce88dece5b394d5dd4332c1572da917b30a.1662264560.git.remckee0@gmail.com>
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On 04.09.22 06:21, Rebecca Mckeever wrote:
> Add function setup_numa_memblock() for setting up a memory layout with
> multiple NUMA nodes in a previously allocated dummy physical memory.
> This function can be used in place of setup_memblock() in tests that need
> to simulate a NUMA system.
> 
> setup_numa_memblock():
> - allows for setting up a memory layout by specifying the fraction of
>    MEM_SIZE in each node
> 
> 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@gmail.com>
> ---
>   .../testing/memblock/scripts/Makefile.include |  2 +-
>   tools/testing/memblock/tests/common.c         | 29 +++++++++++++++++++
>   tools/testing/memblock/tests/common.h         |  4 ++-
>   3 files changed, 33 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..b6110df21b2a 100644
> --- a/tools/testing/memblock/tests/common.c
> +++ b/tools/testing/memblock/tests/common.c
> @@ -72,6 +72,35 @@ void setup_memblock(void)
>   	fill_memblock();
>   }
>   
> +/**
> + * setup_numa_memblock:
> + * Set up a memory layout with multiple NUMA nodes in a previously allocated
> + * dummy physical memory.
> + * @nodes: an array containing the denominators of the fractions of MEM_SIZE
> + *         contained in each node (e.g., if nodes[0] = SZ_8, node 0 will
> + *         contain 1/8th of MEM_SIZE)
> + *
> + * The nids will be set to 0 through NUMA_NODES - 1.
> + */
> +void setup_numa_memblock(const phys_addr_t nodes[])
> +{
> +	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 < NUMA_NODES; i++) {
> +		assert(nodes[i] <= MEM_SIZE && nodes[i] > 0);

I think it would be even easier to get if this would just be a fraction.
E.g., instead of "1/8 * MEM_SIZE" just "1/8". All values have to add up 
to 1.

... but then we'd have to mess with floats eventually, so I guess this 
makes it easier to handle these fractions.


We could use "int" and simply specify the fraction in percent, like

nodes[0] = 50;
nodes[1] = 25;
nodes[2] = 25;

and everything has to add up to 100.


> +		phys_addr_t size = MEM_SIZE / nodes[i];


Hmmm, assuming a single node with "MEM_SIZE", we would get size=1.

Shouldn't this be "size = nodes[i]"

?

-- 
Thanks,

David / dhildenb