Re: [PATCH] MIPS: loongson64: alloc pglist_data at run time

[Jinyang He <hejinyang@loongson.cn>]

On 02/27/2021 02:29 PM, Huang Pei wrote:

> It can make some metadata of MM, like pglist_data and zone
> NUMA-aware
>
> Signed-off-by: Huang Pei <huangpei@loongson.cn>
> ---
>   arch/mips/loongson64/numa.c | 18 +++++++++++++++---
>   1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/arch/mips/loongson64/numa.c b/arch/mips/loongson64/numa.c
> index cf9459f79f9b..5912b2e7b10c 100644
> --- a/arch/mips/loongson64/numa.c
> +++ b/arch/mips/loongson64/numa.c
> @@ -26,7 +26,6 @@
>   #include <asm/wbflush.h>
>   #include <boot_param.h>
>   
> -static struct pglist_data prealloc__node_data[MAX_NUMNODES];
>   unsigned char __node_distances[MAX_NUMNODES][MAX_NUMNODES];
>   EXPORT_SYMBOL(__node_distances);
>   struct pglist_data *__node_data[MAX_NUMNODES];
> @@ -151,8 +150,12 @@ static void __init szmem(unsigned int node)
>   
>   static void __init node_mem_init(unsigned int node)
>   {
> +	struct pglist_data *nd;
>   	unsigned long node_addrspace_offset;
>   	unsigned long start_pfn, end_pfn;
> +	unsigned long nd_pa;
> +	int tnid;
> +	const size_t nd_size = roundup(sizeof(pg_data_t), SMP_CACHE_BYTES);
>   
>   	node_addrspace_offset = nid_to_addrbase(node);
>   	pr_info("Node%d's addrspace_offset is 0x%lx\n",
> @@ -162,8 +165,16 @@ static void __init node_mem_init(unsigned int node)
>   	pr_info("Node%d: start_pfn=0x%lx, end_pfn=0x%lx\n",
>   		node, start_pfn, end_pfn);
>   
> -	__node_data[node] = prealloc__node_data + node;
> -
> +	nd_pa = memblock_phys_alloc_try_nid(nd_size, SMP_CACHE_BYTES, node);
[...]

Hi, all,

Few related to this patch. About memblock, I have a question.

In my own understanding, 3 stages at previous part of arch_mem_init().

stage1: Add memory to memblock.memory at plat_mem_setup().
stage2: parse_early_param() parses parameter about memroy, such as "mem" 
"memmap".
         check_kernel_sections_mem() checks whether the current 
memblock.memory contains the kernel.
         At this stage, user can defined memblock.memory by themselves. 
Also it is the final stage of determining memblock.memory.
stage3: others. use memblock.memory and add them to memblock.reserve.

Calling to memblock_alloc*() should be after the reserve kernel(), see:
     memblock_set_current_limit(PFN_PHYS(max_low_pfn))

(
Here few about this patch: It works no problem, memblock_dump shows:
[    0.000000]  memory.cnt  = 0x2
[    0.000000]  memory[0x0] [0x0000000000200000-0x000000000effffff], 
0x000000000ee00000 bytes on node 0 flags: 0x0
[    0.000000]  memory[0x1] [0x0000000090200000-0x000000025fffffff], 
0x00000001cfe00000 bytes on node 0 flags: 0x0
[    0.000000]  reserved.cnt  = 0x3
[    0.000000]  reserved[0x0] [0x0000000000200000-0x0000000001ed7fff], 
0x0000000001cd8000 bytes flags: 0x0
[    0.000000]  reserved[0x1] [0x00000000fe000000-0x00000000ffffffff], 
0x0000000002000000 bytes flags: 0x0
--->>> [    0.000000]  reserved[0x2] 
[0x000000025fffd6c0-0x000000025fffffff], 0x0000000000002940 bytes flags: 
0x0  <<<---
memblock.bottom_up is not enabled here, and it is not destroy kernel, 
although looks strange.
)

Morever, about "mem" parameter.

When parsing the mem parameter for the first time, all memblock.memory 
is removed.
For NUMA, memblock.memory contain important node information. These 
information are
imported at plat_mem_setup(). Without these node information, the NUMA 
platform
may not be able to use memory correctly.

The mem parameter is rarely used, but it has meaning. For example, 
kdump. I have
done some fixes before, but it looks fool.

Huacai suggested me that use pa_to_nid().

memblock_add(start, size) -> memblock_add_node(start, size, 
pa_to_nid(start))

I think this is a good way. Does anyone have other suggestions?

At last, should the NUMA platform reserve the kernel area after parse 
"mem" rather than before it?

Thanks,
Jinyang