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SubjectRe: [PATCH v3] memblock,arm64: Expand the static memblock memory table
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在 2022/6/7 14:43, Anshuman Khandual 写道:
> Hello Zhou,
>
> On 5/27/22 14:48, Zhou Guanghui wrote:
>> In a system using HBM, a multi-bit ECC error occurs, and the BIOS
>> will mark the corresponding area (for example, 2 MB) as unusable.
>> When the system restarts next time, these areas are not reported
>> or reported as EFI_UNUSABLE_MEMORY. Both cases lead to an increase
>> in the number of memblocks, whereas EFI_UNUSABLE_MEMORY leads to a
>> larger number of memblocks.
>>
>> For example, if the EFI_UNUSABLE_MEMORY type is reported:
>> ...
>> memory[0x92] [0x0000200834a00000-0x0000200835bfffff], 0x0000000001200000 bytes on node 7 flags: 0x0
>> memory[0x93] [0x0000200835c00000-0x0000200835dfffff], 0x0000000000200000 bytes on node 7 flags: 0x4
>> memory[0x94] [0x0000200835e00000-0x00002008367fffff], 0x0000000000a00000 bytes on node 7 flags: 0x0
>> memory[0x95] [0x0000200836800000-0x00002008369fffff], 0x0000000000200000 bytes on node 7 flags: 0x4
>> memory[0x96] [0x0000200836a00000-0x0000200837bfffff], 0x0000000001200000 bytes on node 7 flags: 0x0
>> memory[0x97] [0x0000200837c00000-0x0000200837dfffff], 0x0000000000200000 bytes on node 7 flags: 0x4
>> memory[0x98] [0x0000200837e00000-0x000020087fffffff], 0x0000000048200000 bytes on node 7 flags: 0x0
>> memory[0x99] [0x0000200880000000-0x0000200bcfffffff], 0x0000000350000000 bytes on node 6 flags: 0x0
>> memory[0x9a] [0x0000200bd0000000-0x0000200bd01fffff], 0x0000000000200000 bytes on node 6 flags: 0x4
>> memory[0x9b] [0x0000200bd0200000-0x0000200bd07fffff], 0x0000000000600000 bytes on node 6 flags: 0x0
>> memory[0x9c] [0x0000200bd0800000-0x0000200bd09fffff], 0x0000000000200000 bytes on node 6 flags: 0x4
>> memory[0x9d] [0x0000200bd0a00000-0x0000200fcfffffff], 0x00000003ff600000 bytes on node 6 flags: 0x0
>> memory[0x9e] [0x0000200fd0000000-0x0000200fd01fffff], 0x0000000000200000 bytes on node 6 flags: 0x4
>> memory[0x9f] [0x0000200fd0200000-0x0000200fffffffff], 0x000000002fe00000 bytes on node 6 flags: 0x0
>> ...
>
> Although this patch did not mention about a real world system requiring
> this support, as been reported on the thread, Ampere Altra does seem to
> get benefited. Regardless, it's always better to describe platform test
> scenarios in more detail.
>

I encountered this scenario on Huawei Ascend ARM64 SoC.

>>
>> The EFI memory map is parsed to construct the memblock arrays before
>> the memblock arrays can be resized. As the result, memory regions
>> beyond INIT_MEMBLOCK_REGIONS are lost.
>>
>> Allow overriding memblock.memory array size with architecture defined
>> INIT_MEMBLOCK_MEMORY_REGIONS and make arm64 to set
>> INIT_MEMBLOCK_MEMORY_REGIONS to 1024 when CONFIG_EFI is enabled.
>
> Right, but first this needs to mention that INIT_MEMBLOCK_MEMORY_REGIONS
> (new macro) is being added to replace INIT_MEMBLOCK_REGIONS, representing
> max memory regions in the memblock. Platform override comes afterwards.
>

Add a paragraph before the description,like this?

Add a new macro INIT_MEMBLOCK_MEMORY_REGTIONS to replace
INIT_MEMBLOCK_REGTIONS to define the size of the static memblock.memory
array.

>>
>> Signed-off-by: Zhou Guanghui <zhouguanghui1@huawei.com>
>> Acked-by: Mike Rapoport <rppt@linux.ibm.com>
>> ---
>> arch/arm64/include/asm/memory.h | 9 +++++++++
>> mm/memblock.c | 14 +++++++++-----
>> 2 files changed, 18 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
>> index 0af70d9abede..eda61c0389c4 100644
>> --- a/arch/arm64/include/asm/memory.h
>> +++ b/arch/arm64/include/asm/memory.h
>> @@ -364,6 +364,15 @@ void dump_mem_limit(void);
>> # define INIT_MEMBLOCK_RESERVED_REGIONS (INIT_MEMBLOCK_REGIONS + NR_CPUS + 1)
>> #endif
>>
>> +/*
>> + * memory regions which marked with flag MEMBLOCK_NOMAP may divide a continuous
>> + * memory block into multiple parts. As a result, the number of memory regions
>> + * is large.
>> + */
>
> As mentioned in the previous version's thread,
>
> This comment needs be more specific about this increased static array size, being
> applicable ONLY for MEMBLOCK_NOMAP regions on EFI system with EFI_UNUSABLE_MEMORY
> tagging/flag support.
>

EFI_UNUSABLE_MEMORY is only one type of the MEMBLOCK_NOMAP region, as
shown in the is_usable_memory function. However, However, I currently
have too many memblocks due to this flag.

>> +#ifdef CONFIG_EFI
>> +#define INIT_MEMBLOCK_MEMORY_REGIONS 1024
>
> Although 1024 seems adequate as compared to 128 memory regions in the memblock to
> handle such error scenarios, but a co-relation with INIT_MEMBLOCK_REGIONS would
> be preferred similar to when INIT_MEMBLOCK_RESERVED_REGIONS gets overridden. This
> avoid a precedence when random numbers could get assigned in other archs later on.
>
> $git grep INIT_MEMBLOCK_RESERVED_REGIONS arch/
> arch/arm64/include/asm/memory.h:# define INIT_MEMBLOCK_RESERVED_REGIONS (INIT_MEMBLOCK_REGIONS + NR_CPUS + 1)
> arch/loongarch/include/asm/sparsemem.h:#define INIT_MEMBLOCK_RESERVED_REGIONS (INIT_MEMBLOCK_REGIONS + NR_CPUS)
>
> Something like
>
> #define INIT_MEMBLOCK_MEMORY_REGIONS (INIT_MEMBLOCK_REGIONS * 8)
>

I don't think this is necessary because INIT_MEMBLOCK_REGIONS is not
configurable. The newly added INIT_MEMBLOCK_MEMORY_REGIONS macro is
customized for each platform.

>
> - Anshuman
>

Thanks!

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