Date:   Mon, 13 Jun 2022 06:03:42 +0000
From:   Zhouguanghui <zhouguanghui1@...wei.com>
To:     Anshuman Khandual <anshuman.khandual@....com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "rppt@...nel.org" <rppt@...nel.org>,
        "will@...nel.org" <will@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "xuqiang (M)" <xuqiang36@...wei.com>
Subject: Re: [PATCH v3] memblock,arm64: Expand the static memblock memory
 table

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@...wei.com>
>> Acked-by: Mike Rapoport <rppt@...ux.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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