Re: [PATCH] mips: sgi-ip27: switch from DISCONTIGMEM to SPARSEMEM

Mike Rapoport
2019-09-12T10:58:41Z

On Wed, Sep 11, 2019 at 04:09:39PM +0200, Thomas Bogendoerfer wrote:
> On Tue, 10 Sep 2019 12:32:44 +0100
> Mike Rapoport <rppt@kernel.org> wrote:
>
> > [..]
>
> Patch below works on the same Origin.
>
> Does memblocks_present() deal better with the one reserved page per node
> than sparse_memory_present_with_active_regions() ? Or is there a better
> explanation ? My debug prints didn't make sense out of it...

I think the problem is that when we call
sparse_memory_present_with_active_regions() per node, the page for the node
data of the next nodes is not yet reserved and since memory_present() does
memblock allocations it may use that memory.

We can try to verify that with "memblock=debug" in the command line.

Another thing we could try to rule out the differences between
memblocks_present() and sparse_memory_present_with_active_regions() is to
replace memblocks_present() in your patch with
sparse_memory_present_with_active_regions(MAX_NUMNODES).

> Thomas.
>
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index d50fafd7bf3a..e4b02b5f3487 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -669,6 +669,7 @@ config SGI_IP22
> config SGI_IP27
> bool "SGI IP27 (Origin200/2000)"
> select ARCH_HAS_PHYS_TO_DMA
> + select ARCH_SPARSEMEM_ENABLE
> select FW_ARC
> select FW_ARC64
> select BOOT_ELF64
> @@ -2633,18 +2634,9 @@ config ARCH_FLATMEM_ENABLE
> def_bool y
> depends on !NUMA && !CPU_LOONGSON2
>
> -config ARCH_DISCONTIGMEM_ENABLE
> - bool
> - default y if SGI_IP27
> - help
> - Say Y to support efficient handling of discontiguous physical memory,
> - for architectures which are either NUMA (Non-Uniform Memory Access)
> - or have huge holes in the physical address space for other reasons.
> - See <file:Documentation/vm/numa.rst> for more.
> -
> config ARCH_SPARSEMEM_ENABLE
> bool
> - select SPARSEMEM_STATIC
> + select SPARSEMEM_STATIC if !SGI_IP27
>
> config NUMA
> bool "NUMA Support"
> diff --git a/arch/mips/sgi-ip27/ip27-memory.c b/arch/mips/sgi-ip27/ip27-memory.c
> index fb077a947575..370f2ba14a89 100644
> --- a/arch/mips/sgi-ip27/ip27-memory.c
> +++ b/arch/mips/sgi-ip27/ip27-memory.c
> @@ -410,8 +410,6 @@ static void __init node_mem_init(cnodeid_t node)
>
> memblock_reserve(slot_firstpfn << PAGE_SHIFT,
> ((slot_freepfn - slot_firstpfn) << PAGE_SHIFT));
> -
> - sparse_memory_present_with_active_regions(node);
> }
>
> /*
> @@ -444,6 +442,7 @@ void __init prom_meminit(void)
> }
> __node_data[node] = &null_node;
> }
> + memblocks_present();
> }
>
> void __init prom_free_prom_memory(void)
>
> --
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--
Sincerely yours,
Mike.