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

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Date:   Thu, 12 Sep 2019 11:58:33 +0100
From:   Mike Rapoport <rppt@...nel.org>
To:     Thomas Bogendoerfer <tbogendoerfer@...e.de>
Cc:     Paul Burton <paul.burton@...s.com>, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [PATCH] mips: sgi-ip27: switch from DISCONTIGMEM to SPARSEMEM

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@...nel.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)
> 
> -- 
> SUSE Software Solutions Germany GmbH
> HRB 247165 (AG München)
> Geschäftsführer: Felix Imendörffer

-- 
Sincerely yours,
Mike.