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

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Date:   Thu, 1 Sep 2022 19:08:28 -0500
From:   Rebecca Mckeever <remckee0@...il.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     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 Thu, Sep 01, 2022 at 10:06:48AM +0200, David Hildenbrand wrote:
> On 31.08.22 05:49, Rebecca Mckeever wrote:
> > On Tue, Aug 30, 2022 at 01:17:56PM +0200, David Hildenbrand wrote:
> >> 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?
> >>
> > Without the factor, some of the tests will break if we increase MEM_SIZE
> > in the future (which we may need to do). I could rewrite them so that the
> > factor is not needed, but I thought the code would be over-complicated if
> > I did.
> 
> Independent of the suggestion from Mike, I wonder if we should really
> care about (eventual) MEM_SIZE changes for now if not caring simplifies
> the current code.
> 
Maybe not. I'm going to try Mike's suggestion, but I will keep this in
mind if the code seems too complicated.

> -- 
> Thanks,
> 
> David / dhildenb
> 
Thanks,
Rebecca